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LAT-DS-06124

1. LAT VSC Figure 21 DAQ board cross strapping The figure illustrates that any one time the spacecraft uses one of its interfaces to communicate with one of the LAT s DAQ boards Note that while the figure shows any one communication path as a single wire in actual fact the wire represents communication between the three different types of physical interfaces between SIU and vsc These include i the science interface ii the 1 PPS interface iii the analog temperature and voltage measurements associated with the DAQ board Therefore whenever the cross strapping changes it s changed in unison for all three of these physical interfaces Each one of the four options corresponds to a particular path between the units as is enumerated in Table 6 Table 6 Cross strapping options for the DAQ interface Use Unit VSC LAT Path Primary Redundant Primary Redundant AA yes no yes no AB yes no no yes BA no yes yes no BB no yes no yes When the VSC is initially booted the VSC defaults to using the AA path which corresponds to using the Primary LAT interface communicating with the Primary DAQ board The DagInterface request class see Section 7 7 is used to modify the current cross strapping The class s constructor takes as an argument an enumeration see Section 7 5 Initial public release page 61 The Virtual Spacecraft VSC Users Manual Chapter
2. Oe eccesccccccccccccccccccescesccescecsesoese Oe eccecccccccccccccccccccescesccescecseocoss Oe eccecccccccccccccccceccescesceescecseecoss O I NVULSAS SGNO94S Co 0 C O 0 EO Eo gt o MN E o 0 A E o o O JB Lo 03 gt jemi oJ L ova Nvannaay ovd AYYNIHd SOSAINA O I NVULSAS KO gt O TIEM E O gt O Y E 0 Eo o AM Co 0 E O o O JB o 07 gt oJ L ova NvaNnaay OVA AYYNIHd Figure 15 Corner teststand configuration Figure 16 illustrates how these modules are cabled up This configuration requires the following cables Six 6 LAT DS XXXXX Six 4 LAT DS XXXXX Six 5 LAT DS xxxxx Initial public release page 49 The Virtual Spacecraft VSC Users Manual Chapter 2 Hardware Version Issue 1 4 2 LAT DS XXXXX _ LAT DS XXXXX _ LAT DS XXXXX _ gt Figure 16 Internal Connectivity LAT VSC page 50 Initial public release The Virtual Spacec
3. 7 public 8 virtual Telemetry 9 public 10 Telemetry amp operator const Telemetry amp 11 y 4 8 Science Science packets are simply sub classed from GenericTelemet ry see Section 4 6 with the template packet size argument satisfied Science packets are fixed size independent of the actual allocated payload size 4096 bytes That is the maxPayload function will return 4096 bytes less the size of the header Science packets are delivered on the science stream see Section 7 2 Listing 7 Class definition for Science 1 class Science public GenericTelemetry lt 4096 gt 2 public constructors 3 Science short apid 4 unsigned secs unsigned usecs 5 SeqFlags flags alone unsigned short seqNum 0 6 Science const Science amp 7 public 8 virtual Sciencel Jis public 10 Science amp operator const Science amp 11 public 12 unsigned short pad const 133 const unsigned data const 14 unsigned sizeofData const 15 y 4 8 1 Member synopsis pad Returns the value of the so called pad word of the corresponding CCSDS packet This function has no arguments and throws no exceptions Initial public release page 87 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 data Returns a pointer to the datagram portion of the corresponding CCSDS packet This function has no arguments and throws no exceptions sizeofDa
4. Returns the requested value of the VERSION field of the CCSDS packet header see 16 and 17 Only the low order three bits of the returned value are significant Note that this function is virtual and may be over loaded by a derived class By default the member function is not over loaded the function returns a value of seven 7 This function has no arguments and throws no exceptions Initial public release page 83 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 recordedChecksum Returns the requested value for the initial value of the packet s recorded checksum Note that as soon as the TeleCmnd s copy method see Section 4 4 is called this value will no longer be the packet s recorded checksum Instead the packet will have the computed checksum Note that this function is virtual and may be over loaded by a derived class By default the member function is not over loaded the function returns a value of zero 0 This function has no arguments and throws no exceptions 4 6 Generic Telemetry packet This class specifies a GLAST specific generic CCSDS telemetry packet All GLAST telemetry packets share a common set of attributes In particular the isTelecommand function always returns FALSE A time stamp This time stamp specifies when the telemetry was acquired Acquisition time is represented by two 32 bit quantities the acquisition time in granularity of both
5. O CO o O E O gt OC S O gt gt O O o O IE CO o O T E O Figure 14 VSC 850 module 2 8 LAT Monitoring interface Initial public release page 47 The Virtual Spacecraft VSC Users Manual Chapter 2 Hardware Version Issue 1 4 2 2 9 VSC Configurations 2 9 1 The Testbed As shown in Figure 15 the testbed configuration consists of the following modules One 1 21 slot 6U VME crate One 1 MVE2304 Single Board Computer Two 2 PMC 1553B 1553 interface modules One 1 TTM637VME GPS receiver Two 2 VSC SCI science modules One 1 vSC DSC discrete interface module One 1 Systran 1 0 substrate with four 4 industrial packets One vsc 850 LAT interface module page 48 Initial public release The Virtual Spacecraft VSC Chapter 2 Hardware Users Manual Version Issue 1 4 2 8 10 11 12 MVE2304 TTM637VME VSC SCI VSC SCI VSC DSC vme DATA GPSANT O DATA vme DY VSC SCI SCIENCE INTERFACE DS 06654 VSC SCI SCIENCE INTERFACE DS 06654 LAT DSC VME IN SOSAINA VSC DSC DISCRETE INTERFACE DS 06656 XMT RCV XMT RCV XMT RCV SALANIIN Oe eccecccccccccccccccceccescesccescecceooess Oe eccecccccccccccccccccccescesccesceosescess
6. the LAT is responsible for insuring its clock is consistent both within itself and the FES Front End Simulator In this fashion time is coherently maintained between spacecraft instrument and event simulation The LAT insures consistency between it and the FES by page 28 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 driving the FES s clock using the LAT external test connector see 19 Coherency between vsc and LAT is a bit more complex and requires understanding how the VSC represents and keeps time 1 3 1 Time representation The VSC represents time as an unsigned 32 bit value in which one count equals one second A value of zero corresponds to the time at 00 00 00 0 hours at January 1 2001 This is the common unit of time measurement between spacecraft and instrument see 8 The agreed upon current time between VSC and LAT is maintained within the VSC s observatory time base The time base is updated once a second see Section 1 3 2 therefore its value at any one point corresponds to the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 The vscC uses the observatory time base to determine when a telecommand becomes due Section 1 3 Set the period time for all ancillary commands time tag any telemetry the VSC might source time tag any necessary timing information sent to the LAT In short wherever the VS
7. FSM with five states These states are 1 Stopped In this state all queues are nominally empty the VSC accepts all telecommands time does not increment scheduling is disabled 2 Paused In this state the state of all queues is irrelevant the VSC accepts all telecommands time does not increment scheduling is disabled 3 Running In this state the state of all queues is irrelevant the VSC accepts all telecommands time increments scheduling is enabled 4 Flushing queues In this state the state of all queues is indeterminate the VSC rejects all telecommands time does not increment scheduling is disabled 5 Setting time In this state the state of all queues is irrelevant the VSC rejects all telecommands time does not increment scheduling is disabled Transitions between states are triggered by the execution of a scheduler request Commands of this type are scheduled for execution within the phase discussed in Section 1 4 3 2 This command has two functions State transition Requests a state transition The function code enumerates the new state requested of the scheduler The telecommand parameter is ignored The set of potential state transitions are Initial public release page 37 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 Start put the VSC into a state of running Pause put the VSC into a paused sta
8. The constructor throws no exceptions A 2 2 Member synopsis validate dispose This method will be called whenever a CCSDS science packet arrives which is to be assembled into the resulting datagram The default implementation is a no op and simply returns The argument is a reference to the arrived CCSDS science packet Note that the argument referenced by this method and any objects it may reference is ephemeral When the method returns these objects are no longer accessible Consequently any information in these objects which the user finds necessary to persist across calls to this method must be copied Note This function is pure virtual and therefore its implementation must be provided by a derived class This function returns no value and throws no exceptions This method is called once per assembled datagram It will be called immediately after all the packets which constitute the datagram have been processed The first argument is a reference to the assembled datagram see 27 The second argument is these number of fragments CCSDS science packets used in the assembly of the datagram Note that the argument referenced by this method and any objects it may reference is ephemeral When the method returns these objects are no longer accessible Consequently any information in these objects which the user finds necessary to persist across calls to this method must be copied Note This function is pure virtual and therefore its
9. printf Payload size is d bytes n packet sizeofPayload printf Dump of first word of payload n packet payload return This function is passed the packet to decode and print along with a character string to print as the decode prefix Now in order to simplify the examples in Section 3 5 2 gratuitously wrap this function in a class which accepts the packet title as an argument to its constructor class Dump public Dump const char title title title Dump public void decode VscCcsds Telemetry amp private const char title 1 Of course this function would in practice be much more sophisticated page 64 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 Next a class derived from TelemetryHandler see Section 5 3 is defined which contains this function class MyHandler public TelemetryHandler public MyHandler const char title TelemetryHandler _dump title MyHandler private Dump _ dump MyHandl er contains an object of type Dump A handler disposes of its caught packets through its process method The method is passed as an argument the arrived packet As this method is virtual MyHandler provides the implementation void MyHandler process VscCcsds Telemetry amp packet _ decode packet ret
10. see 8 Note that one field of this command specifies whether or not the source of the 1 PPS signal was a GPS receiver The value of this field is independent of which of the two types of sources are used by the VSC 1 4 Routing and scheduling requests The command and control of the VSC is governed by five different types of objects inPorts Delivers request packets off a stream routers Routs arrived requests based on APID to their appropriate queue queues Holds telecommands in time order for their later execution scheduler Examines once a second each queue to determine whether there are any telecommands due for execution Scheduling is discussed in Section 1 4 3 page 30 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 drivers Transforms telecommands to appropriate LAT interface commands Sends these commands to the LAT The flow of command and control through these objects is illustrated within Figure 4 commanding stream command port routing transitions stored immediate ancillary stored immediate control control control command command command queue queue queue queue queue queue a a schedule processing schedule processing Figure 4 Command and Control flow through the vsc 1 4 1 Routing The VSC receives direction through a specific type of tele
11. while the 4 attitude command is always sent somewhere within slot nineteen Slot number 5 spans the interval from 200000 to 239999 microseconds while slot number 19 spans the interval from 760000 to 799999 microseconds The proxy interface provides the application with three different options in terms of how the ancillary slots are populated page 72 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 For example this code snippet establishes a default sequence Do not fill This is the default behaviour after the VSC boots Of course this option is not very useful with respect to correct operation of the LAT and is intended primarily as a tool to commission and debug the processing of the ancillary sequence by FSW on the LAT If a default sequence see below has been established one can return to not filling the ancillary slots by calling the schedule member of the Proxy class with no arguments Fill with the same set of commands independent of period The application defines a specific set of seven commands sends these commands to the VSC which transmits the same set at every period to the LAT This option is attractive when LAT FSW either needs to dwell on a specific set or doesn t care what the contents of the commands are as long as the appropriate slots are filled The application specifies a fixed sequence by calling the schedule member of
12. 3 A P Waite updated 30 November 2004 page 4 Initial public release The Virtual Spacecraft VSC References Users Manual Version Issue 1 4 2 22 23 24 25 26 27 28 29 The GLT Electronics Module Programming ICD specification Michael Huffer LAT TD 01545 See the LAT Flight Software web site for the traveller documentation for LPA currently undefined See the LAT Flight Software web site for the traveller documentation for datagrams currently undefined See the LAT Flight Software web site for the traveller documentation for LCI currently under project APP package LCT The EBM Electronics Module Programming ICD specification Michael Huffer LAT TD 01546 The DataFlow Public Interface Michael Huffer LAT TD 01546 Data Sheet for the Goodrich Model 0118MF High Reliability Surface Temperature Sensor http www sensors goodrich com literature list shtml Data Sheet for the YSI 44900 Series Thermistor GSFC S 311 P 18 http www ysitemperature com tech home html Note For additional resources refer to the LAT Electronics DAQ Critical Design Requirements List On the LAT Electronics Data Acquisition amp Instrument Flight Software page http www glast slac stanford edu Elec_DAQ Elec_DAQ_home htm click Hardware and then click List of all documents Initial public release page 5 The Virtual Spacecraft VSC Document Control Sheet Use
13. 3 Using the proxy interface Version Issue 1 4 2 which specifies which one of the four cross strapping options should be selected For example to communicate with the primary DAQ board through the VSC s redundant interface vsc execute DagqInterface AB Or to restore the cross strapping to its initial value vsc execute DagInterface 3 3 5 Enabling the Science Interface The science interface on the spacecraft contains a data enable This enable is the so called DEVICE READY LINE In order to enable or disable the SSR interface one instantiates the Ssr class see Section 7 11 When the VSC is initially booted the science interface is disabled Until the science interface is enabled any science data sent to the VSC by the LAT remains queued on the LAT Once the interface is enabled the DEVICE READY LINE is asserted this queued data will be received on the VSC and forwarded to the proxy interface as science telemetry see 8 For example to enable science data vsc execute Ssr Enable and to disable the science data vsc execute Ssr Disable 3 3 6 Enabling Diagnostic Monitoring The spacecraft has the responsibility to monitor ninety two 92 different temperatures and voltage whose origin is the LAT This information is acquired and brought to the ground as one component of the spacecraft s telemetry In order to mitigate against single point fa
14. B NASA Goddard Space Flight Center April 2002 8 GLAST LAT to Spacecraft Interface Control Document Spectrum Astro Inc February 2003 9 GLAST Spacecraft Interface Board Hardware Specification LAT Hardware Specification Document 10 LTX User Manual V1 1 0 LAT FSW User Manual August 2003 11 Military Standard 1553B Notice 2 United States Department of Defence September 1986 12 Military Standard 1553B Aircraft Internal Time Division Command Response Multiplex Data Bus United States Department of Defence September 1978 13 MSG User Manual LAT Flight Software User Manual 14 PBS Package Documentation LAT Flight Software Code Documentation 15 PMC 1553 Reference Manual Rev 1 2 Alphi Technology Corporation June 1998 16 Recommendation for Space Data System Standards Advanced Orbiting Systems Networks and Data Links Architectural Specification Blue Book 701 0 B 3 Consultative Committee for Space Data Systems June 2001 17 Recommendation for Space Data System Standards Telecommand Part 3 Data Management Service Architectural Specification Blue Book 203 0 B 1 Consultative Committee for Space Data Systems January 1987 18 Telecommand and Telemetry Formats LAT TD 02659 19 GASU Based Teststands A hardware and software Primer Michael Huffer LAT TD 03664 20 Symmetricom TTM635 637VME Time and Frequency Processor revision B Users Guide 8500 0138 February 2004 21 LAT Flight Software CMX Manual version V2 2
15. B 2 Telemetry from the 850 board The spread sheet illustrated in Figure B 1 enumerates the quantities monitored by the 850 board and encapsulated in the telemetry packet whose APID is defined in Section B 2 7 Each entry in the spread sheet corresponds to one specific monitored quantity For each quantity the spread sheet specifies the relative location of its data sensor type and description Data offsets are described in units of 16 bit decimal words with offset zero 0 beginning immediately following the standard telemetry header i e the start of the packet s payload Initial public release page 135 The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring System Version Issue 1 4 2 For example offset eight 8 corresponds to a measurement of the GASU s temperature on its primary DAQ board The sensor type is thermistor which specifies temperature as measured through a thermistor page 136 Initial public release The Virtual Spacecraft VSC Appendix B_ Telemetry from the Monitoring System Users Manual Version Issue 1 4 2 B 2 7 APID 0x00A8 Offset a a mis 2 22121718 13 813 8 lt lt lt lt lt lt TU v ala I gt FE FIFA Sla a 2 2 2 9 3 2 22 8 3 z lt lt lt lt lt lt U Conversion hermistor Primary SIU Temperature P Primary SIU Voltage hermistor Primary SIU Spare Temperature P R f ri
16. Hardware Version Issue 1 4 2 2 4 The Science interface VSC SCI vme DATA o e FES PPS OUT OUT FES PPS IN IN LAT VSC SCI SCIENCE INTERFACE DS 06654 XMT RCV Figure 11 Science interface page 44 Initial public release The Virtual Spacecraft VSC Chapter 2 Hardware Users Manual Version Issue 1 4 2 2 5 The Discrete interface VSC DSC DSC VME IN LAT VSC DSC DISCRETE INTERFACE DS 06656 XMT RCV a Figure 12 Vsc components Initial public release page 45 The Virtual Spacecraft VSC Chapter 2 Hardware Users Manual Version Issue 1 4 2 2 6 Digitizer SYSTRAN SOSSAINA AO BO co DO E O I NVULSAS Figure 13 Digitizer 2 LAT Cable interface page 46 Initial public release The Virtual Spacecraft VSC Chapter 2 Hardware Users Manual Version Issue 1 4 2 xmt rev xmt rev xmt rcv eecccocococoooocoocosocoooococoooooooooooooo CO VSC 850 nda nis L ova LNVONNdGaY OVA AYVINIed co O EO O E O
17. MyHandler public Housekeeping Housekeeping And the constructor s implementation Housekeeping Housekeeping MyHandler Housekeeping handle 0x200 Ox25F The implementation simply calls Router s range method passing both the necessary low and high APIDs Once registered with a router the handler will catch and process those packets whose APIDs fall only within the housekeeping range However what happens to those packets which do not fall within this range specified by the handler In such a case these packets are delivered to a router s catchall method as discussed in Section 3 5 What if a handler wishes to catch more then one range For example assume poorly the Housekeeping handler is required to catch and process not only LAT housekeeping telemetry but also alert telemetry Alert APIDs vary from 340 to 39F hexadecimal In sucha case the range method is used twice Housekeeping Housekeeping MyHandler Housekeeping handle 0x200 0x25F housekeeping handle 0x340 0x39F alert 3 5 Routing Incoming telemetry Telemetry arrives from the VSC to the proxy interface as a series of CCSDS packets see 4 7 and 4 8 As these packets arrive they need to be dispatched to a set of appropriate telemetry handlers telemetry handlers are discussed in Section 3 4 In order to dispatch arriving telemetry the appl
18. No transmit port To be written 7 15 3 Network Transmit Failure To be written Initial public release page 125 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 page 126 Initial public release The Virtual Spacecraft VSC Users Manual Appendix A The Datagram support package Version Issue 1 4 2 Appendix A The Datagram support package By LAT convention information passed on the science stream is always organized in units of datagrams see 23 A Datagram is a common structure used to encapsulate all science data created and transmitted by Flight Software FSW Much but not all of the complication of processing science as opposed to housekeeping telemetry is due to this encapsulation For example while in principal datagram size is unbounded this is not the case for CCSDS packets To deal with this eventuality FSW transmits datagrams as a series of one or more science CCSDS packets with the same APID In other words a datagram may span CCSDS science packets Sequencing information within the packet see 16 is used to identify which packet is which part of a datagram The principal function of this package is therefore the assembly of CCSDS science packets into datagrams An assembled datagram is represented by the Datagram class see 27 As packets for these datagrams arrive potentially out of order they must be sequenced before assembly Further as packet tr
19. Section 4 7 The implementation of this class simply derives from Handler see Section 5 2 and satisfies the template argument with the class representing a telemetry packet Any application which handles telemetry packets is expected to sub class from TelemetryHandler and provide an implementation of its process method Listing 13 Class definition for TelemetryHandler 1 class TelemetryHandler public Handler lt VscCcsds Telemetry gt 5 3 1 Constructor synopsis see Section 5 2 5 3 2 Member synopsis see Section 5 2 5 4 Science Handler This class specifies a handler for a science packets see Section 4 8 The implementation of this class simply derives from Handler see Section 5 2 and satisfies the template argument with the class representing a science packet Any application which handles science packets is expected to sub class from ScienceHandler and provide an implementation of its process method Listing 14 Class definition for ScienceHandler 1 class ScienceHandler public Handler lt VscCcsds Science gt page 98 Initial public release The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 5 4 1 Constructor synopsis see Section 5 2 5 4 2 Member synopsis see Section 5 2 5 5 Telecommand Handler This class specifies a handler for a telecommand packets see Section 4 4 The implementation of this class simply derives
20. VSC diagnostic This stream transmits solicited CCSDS telemetry from the VSC to the proxy interface Solicited telemetry is requested by the user s of the proxy interface by queuing download requests see Section 7 12 The set of CCSDS packets which constitute the allowed telemetry on this stream are enumerated and described in appendix B Note that this stream is independent of the VSC telemetry stream used to receive unsolicited telemetry sourced by the vsc That stream is the VSC telemetry stream described below LAT diagnostic This stream transmits CCSDS telemetry from the VSC to the proxy interface This telemetry is the LAT diagnostic telemetry which was brought into the VSC through the 1553 interface between VSC and LAT The set of CCSDS packets which constitute the allowed telemetry on this stream are enumerated and described within the The GLAST Command and Telemetry Database see 18 Note that this stream is independent of the LAT telemetry stream That stream is the LAT telemetry stream described below VSC telemetry This stream transmits unsolicited CCSDS telemetry from the VSC to the proxy interface An example of such telemetry would be the voltage and temperatures of the LAT which are measured by the vsc The set of CCSDS packets which constitute the allowed telemetry on this stream are enumerated and described in xxx Note that this stream is independent of the LAT telemetry stream used to receive housekeeping and diagnos
21. a value of zero 0 to 999 999 decimal The next three arguments are quaternions which correspond to the position of the Spacecraft with the first of the three arguments corresponding to the position with respect to the X axis the second with respect to the Y axis the third with respect to the Z axis The last three arguments correspond to the velocity of the spacecraft with the first of the three arguments corresponding to the position with respect to the X axis the second with respect to the Y axis the third with respect to the Z axis The ninth argument is an enumeration corresponding to the satellite s GNC mode The tenth argument specifies the fraction of SSR storage used for science data not yet down linked This fraction is expressed as a number between zero 0 and 100 percent The last argument is a bit list representing the current state of the spacecraft See 7 for an explanation of the possible states The Ancillary telecommands are transmitted for execution by objects of the class described in Section 7 2 4 11 2 Member synopsis usecs Returns the time within the execution period to schedule the telecommand This time is specified in micro seconds and may range from a value of zero 0 to 999 999 decimal This function has no arguments POSITION X Returns the X axis component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to t
22. consume Packets arrive asynchronously on three different telemetry streams see Section 7 2 An application makes the connection between their handler and packets arriving on a stream by registering their handler with an application specific router see Section 6 2 In turn this router is registered with a stream The class specification for the abstract handler is found in Listing 12 An application is not expected to directly inherit from this class Instead an application will sub class from one of these three specific handlers TelemetryHandler see Section 5 3 ScienceHandler see Section 5 4 TeleCmndHandler see Section 5 5 Listing 12 Class definition for Handler 1 template lt class T gt Handler public VscList Link lt Handler gt 2 protected constructors 3 Handler 4 public 5 virtual Handler 6 public 7 virtual void process T amp 0 8 public 9 Handler lt T amp gt next const 10 public Ts bool catchable const Te const 12 public 13 const ApidRange head const 14 const ApidRange last const 15 void handle unsigned short 16 void handle unsigned short low unsigned short high 17 page 96 Initial public release The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 5 2 1 Constructor synopsis Handler The constructor sets its internal list of APID ranges see Section 5 6 to
23. each of the classes of the package Each class description begins with a class specification The specification syntax is C as this is implementation language for both the VSC and its proxy interface Following the specification is a short synopsis of the class s constructors and members The package description ends with an enumeration of the exceptions the classes of the package may throw 1 2 2 Header files and name spaces Each package has its own name space The name of this space corresponds to the name of the package Each class within the package has two associated files A file with an extension hh containing the interface class description A file with an extension of cc containing the class s implementation Each file name has the form PackageName ClassName For example the class description file of the CCSDS telemetry packet is a part of the VscCCSDS package and would therefore have the file name VscCcsds Telemetry hh while its corresponding implementation file would have the name VscCcsds Telemetry cc 1 2 3 Configuration management The code base is managed using the FSw Flight Software management and build system see 21 The code base is organized under its own project The project name is VSC The vsc package and constituent organization remains to be described 1 3 Observatory time The VSC has the responsibility for maintaining consistent time between it and the LAT In turn
24. empty This list corresponds to the set of APIDs whose corresponding packets the handler is willing to catch If the list is empty the handler will catch any packet independent of APID This constructor throws no exceptions 5 2 2 Member synopsis process next catchable head last This method would be called whenever the cat chable function see below matches a CCSDS packet against its APID list The argument to the method specifies a reference to the packet to be processed This function returns no value and throws no exception If this handler resides on a router list see Section 6 2 this method returns a reference to the handler on the list following this handler If the handler is not on a list the method returns a reference to itself If the handler is at a router s tail it returns a reference which is equal to the list itself This function throws no exception This method determines whether the handler could catch and process a particular incoming CCSDS packet This packet is represented by the input argument which is a reference to a CCSDS packet see Section 4 2 This involves traversing the handler s internal range list For each range on this list if the packet s APID falls within that range the handler should catch the packet If the range list is empty the handler would catch any packet If the packet would be caught this method returns a TRUE value If the packet would not be caught the method retur
25. follows the APID is set to the value of the constructor s first argument the secondary header SH is set the packet type identifier T is set indicating this is a telecommand the packet version is set to zero indicating a version 1 packet the sequence count is set to zero the sequence flag is set to Standalone packet 3 the packet length is set to zero 0 The constructor throws no exceptions Packet short apid SeqFlags unsigned short seqNum This constructor initializes the CCSDS primary header of the packet corresponding to the object as follows the APID is set to the value of the constructor s first argument the secondary header SH is set the packet type identifier T is cleared indicating this is a telemetry packet the packet version is set to zero indicating a version 1 packet Initial public release page 79 The Virtual Spacecraft VSC Chapter 4 CCSDS package Users Manual Version Issue 1 4 2 the sequence count is set to the value specified by the constructor s third argument If this argument is omitted the sequence count is set to zero the sequence flag is set to the value specified by the constructor s second argument the packet length is set to zero 0 The constructor throws no exceptions 4 3 2 Member synopsis apid Returns a value corresponding to the application identifier APID for the corresponding CCSDS packet APIDs range from zero
26. for its corresponding field Listing 4 Class definition for Mangle al 2 3 4 5 6 7 8 E 10 Tis 12 public public public class Mangle public constructors Mangle virtual Mangle virtual bool T const virtual bool SH const virtual unsigned short version const virtual unsigned short recordedChecksum const 4 5 1 Constructor synopsis Just the default 4 5 2 Member synopsis SH version Returns the requested state of the T field of the CCSDS packet header see 16 and 17 The T field determines whether or not the packet declares itself as a telecommand A value of TRUE specifies the T field is set a FALSE value that the field is clear Note that this function is virtual and may be over loaded by a derived class By default the member function is not over loaded the function returns a FALSE value This function has no arguments and throws no exceptions Returns the requested state of the SH field of the CCSDS packet header see 16 and 17 The SH field determines whether or not the packet has a secondary header A value of TRUE specifies the SH field is set a FALSE value that the field is clear Note that this function is virtual and may be over loaded by a derived class By default the member function is not over loaded the function returns a FALSE value This function has no arguments and throws no exceptions
27. function throws no exceptions high This function returns the larger of the two APIDs specifying the range If the range s extent corresponds to only one APID the value returned will be equal to the returned value of the low function described above This function throws no exceptions page 100 Initial public release The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 5 7 Exceptions none Initial public release page 101 The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 page 102 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 6 The Routing package Version Issue 1 4 2 Chapter 6 The Routing package The classes of this package allow the user to register an application specific object to route incoming CCSDS packets on a stream to be caught by an appropriate handler Objects which catch and route CCSDS packets are called Routers Incoming packets are carried on the streams discussed in Section 1 1 These packets take three different forms i 1553 Diagnostics and housekeeping telemetry ii Science telemetry which includes both science housekeeping and events iii Telecommands For each of type of packet there is a corresponding router however all three routers are derived through a common base class see Section 6 2 as they all have exactly the same form except for the type of the packe
28. implementation must be provided by a derived class This function returns no value and throws no exceptions unexpected This method will be called whenever a CCSDS science packet arrives at the assembler which was not expected For example the assembler may be waiting for the last packet of a sequence and is sent instead the first packet of the sequence The first argument is a reference to the unexpected CCSDS packet The second argument is the expected state expressed as a value from zero to fifteen decimal The third argument is the expected sequence number Note This function is pure virtual and therefore its implementation must be provided by a derived class This function returns no value and throws no exceptions maxDatagramSize This method returns the maximum size in bytes of any expected assembled datagram This value was passed as an argument to the constructor This function has no arguments and throws no exceptions Initial public release page 129 The Virtual Spacecraft VSC Users Manual Appendix A The Datagram support package Version Issue 1 4 2 A 3 LCI Assembler This class allows for the assembly of datagrams which originated from FSW s LAT Charge Injection LCI system see 25 The implementation of this class is straightforward itinherits from Assembler see Section A 2 determines and sets the maximum size of any expected datagrams determines and registers the APIDs corresponding to
29. receiver and can therefore be assumed to be stable with respect to the LAT s clock If the value returned is TRUE the telecommand was synthesized with respect to the VSC s GPS receiver If the value returned is FALSE the telecommand was synthesized with respect to the VSC s local clock This function has no arguments and throws no exceptions Returns a value which specifies the time corresponding to the next transmission of the 1 PPS signal sent to the LAT The returned value will also be equal to the time at which the telcommand will be executed plus one 1 Time is represented as the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 This function has no arguments and throws no exceptions 4 13 Exceptions None page 94 Initial public release The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 Chapter 5 The Handling package The classes of this package allow the user to register an application specific object to catch and handle incoming CCSDS packets Objects which catch and process CCSDS packets are called Handlers Incoming packets are carried on the streams discussed in Section 1 1 These packets take three different forms i 1553 Diagnostics and housekeeping telemetry ii Science telemetry which includes both science housekeeping and events iii Telecommands For each of type of packet there is a corresponding handler however all three handl
30. reference to an object containing these parameters The constructor will replace its own internal copy of these parameters with the parameters specified by the argument The constructor throws the exceptions Section 7 15 2 and Section 7 15 3 7 2 2 Member synopsis vscDiagnostic Creates a connection to the VSC s diagnostic stream and registers an application specific router to process the diagnostic telemetry acquired by the vsc and returned through the stream The set of potential diagnostic telemetry returned by the VSC is described in appendix B The router s code is executed in the context of the thread named VscDiagnosticThread The priority of the thread is specified by adding zero 0 to a common base priority The base priority is returned by the basePriority function of the class described in Section 7 14 The functions s argument specifies a reference to the router to process incoming packets see Section 6 2 The router will be called back once for every received CCSDS telemetry packet One can only register a router once per stream If this member function has been previously called the exception described in Section 7 15 1 will be thrown If this member function cannot transmit the connection request to the VSC due to a network error the exception described in Section 7 15 3 will be thrown This member function returns no value vscTelemetry Creates a connection to the VSC s telemetry stream and registers an application
31. relative priority between the five potential threads is fixed by the proxy interface and cannot be changed These relative priorities are implicit in the ordering of Table 7 For example the highest priority thread is associated with the VSC diagnostic stream while the lowest is associated with the science stream While relative priorities are immutable the base priority of the five threads can be changed by the application see Section 7 14 This should only prove necessary in the eventuality that the proxy interface s threads conflict with the priorities of other application threads page 68 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 As an example suppose the router described in Section 3 5 was required catch and process arriving LAT telemetry This requires the router to first be instantiated and second passed to the appropriate member function to be registered vsc latTelemetry new MyRouter 3 5 2 APID dispatching The previous section demonstrated how an application constructs a router which dispatches all packets belonging to a single handler However the interface also supports dispatching packets based on APID to different handlers In the same fashion that a handler contains a list of APIDs a router contains a list of handlers For example assume we wish to process alert telemetry differently then housekeeping te
32. the epoch 00 00 00 0 hours at January 1 2001 The seven commands transmitted are represented by the seven arguments following the period argument Relative to each other these commands are transmitted to the LAT in argument order The relative time structure between these and other telecommands transmitted to the LAT is discussed in Section 1 4 The second argument is a reference to the first of the five different attitude packets see Section 4 10 sent to the LAT within the scheduled one second period The third argument is a reference to the time tone packet sent to the LAT period see Section 4 12 within the scheduled one second period The fourth fifth and sixth arguments are references to the next three attitude packets sent to the LAT within the scheduled one second period The seventh argument is a reference to the single ancillary data packet see Section 4 11 sent to the LAT within the scheduled one second period The eight and last argument is a reference to the fifth and last attitude packet sent to the LAT within the scheduled one second period This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 Initial public release page 115 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 73 Scheduler control request Constructs a change scheduler state request The new state is specified as an enumerati
33. the scheduler attempts to queue to the LAT through the Vsc s 1553 interface the telecommands on the work lists associated with the ancillary immediate and stored command queues see Table 4 These telecommands provide direction to the LAT For example the telecommand used to take the SIU out of primary boot see 8 for a list of these telecommands The spacecraft and consequently VSC limits transmission to at most one command per slot Five of these slots are not accessible to the user therefore the maximum number of proxy originated commands which can be sent to the LAT during any one period is limited to twenty Seven of these slots are pre allocated to the ancillary sequence the so called magic seven and each particular ancillary command is mapped to a specific slot For example the timetone command is always sent on slot five see Figure 6 for the complete assignments This leaves thirteen slots allocated to arbitrary commands to be scattered within arbitrary slots The scheduler fills any given slot depending on whether the slot would be occupied with either an ancillary or generic command Ifthe slot specifies an ancillary command the telecommand at the head of the work list associated with the ancillary queue is removed and transmitted If when removing a command from this list the list was empty a default command is looked for If the default is present it is transmitted If a default command is not found the s
34. thrown If this member function cannot transmit the connection request to the VSC due to a network error the exception described in Section 7 15 3 will be thrown This member function returns no value latScience Registers an application specific router to process telemetry received by the VSC on the science telemetry stream The router s code is executed in the context of a thread named VscScienceThread The priority of the thread is specified by adding four 4 toa common base priority The base priority is returned by the basePriority function of the class described in Section 7 14 The functions s argument specifies a reference to the router to process incoming packets see Section 6 2 The router will be called back once for every received CCSDS telemetry packet One can only register a router once per stream If this member function has been previously called the exception described in Section 7 15 1 will be thrown If this member function cannot transmit the connection request to the vsc due to a network error the exception described in Section 7 15 3 will be thrown This member function returns no value execute Scheduler amp Transmits a scheduler requests on the command stream to the VSC where these requests are then queued on the VSC for subsequent execution as soon as the VSC has the capability to do so The scheduler requests to execute are represented by the function s arguments Relative to each other these commands a
35. 0 to FFFF hex This function has no arguments and throws no exceptions isTelecommand Returns an boolean identifying whether or not the corresponding CCSDS version segqNum segFlags length 4 4 TeleCmnd packet is a command or telemetry packet If the value returned is TRUE the packet is a telecommand packet If the value returned is FALSE the packet is a telemetry packet This function has no arguments and throws no exceptions Returns a value corresponding to the version identifier for the corresponding CCSDS packet The version identifier for all LAT CCSDS packets is zero 0 used to indicate a Version 1 packet This function has no arguments and throws no exceptions Returns a value corresponding to the sequence number for the corresponding CCSDS packet This function has no arguments and throws no exceptions Returns an enumeration specifying the packet s location in a sequence of data which could potentially span multiple packets The return value can have one of the four possible values enumerated within Table 8 This function has no arguments and throws no exceptions Returns the length of the packet less the primary header six bytes For reasons which escape me the value is actually the value specified above less one 1 The length is expressed in units of bytes The length is inclusive of any secondary header As all LAT CCSDS packets are a multiple of 16 bits words the value returned will always be odd This fu
36. 2 describes the telemetry packet produced by the 468 board In actuality to mitigate against single point failure data for these 102 quantities are brought twice into the VSC however only one set is transmitted at any one time see Section 3 3 6 Each packet contains as its last field a boolean which identifies whether this data originates from the primary or redundant set of signals A value of one 1 indicates the primary signals and a value of two 2 indicates the redundant signals For each quantity monitored the corresponding VSC digitizer produces 11 bits of magnitude and one bit of sign This 12 bit value is sign extended to a 16 bit value before transmission B 1 Unit conversion There are six different types of conversion necessary to translate between raw sign extended ADC counts and engineering units The relationship between conversion type and monitored quantity is enumerated in the spreadsheets of figures B 1 and B 2 The following six sections define for each of these six conversion types the necessary conversion equation Initial public release page 133 The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring System Version Issue 1 4 2 B 1 1 LAT voltage LatV Equation 1 converts voltage sensor counts v to voltage V where v is the signed 16 bit ADC value and V is measured in volts V C C X Vy where 1 Cy 20V c 4096counts B 1 2 BPU voltage BpuV
37. 4 2 Listing 25 Listing 26 Listing 27 Listing 28 Listing 29 Listing 30 Listing 31 Listing 32 Listing A 1 Listing A 2 Listing A 3 goog e ee We tp 119 120 121 122 122 123 124 124 128 130 131 Class definition for DaqInterface Class definition for ToggleLines Class definition for Reset Class definition for Monitor Class definition for SsrInterface Class definition for Download Class definition fortGrb Class definition for Parameters Class definition for Assembler Class definition for LciAssembler Class definition for LpaAssembler page 20 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 Chapter 1 Introduction Physically the VSC consists of a VME crate with a Single board Computer SBC and up to five different modules The processor executes code operating under VxWorks as its real time kernel As its principal responsibility the VSC emulates the spacecraft s S C side of the interface between spacecraft and LAT A series VME modules implement the physical interface These modules are controlled and managed with software residing in the SBC This software constitutes the VSC s internal implementation which is not described in this document In addition to implementing the ICD the VSC also includes an external software interface The external interface allows an application to control and manage the VSC remotely The rem
38. C Table of Contents Users Manual Version Issue 1 4 2 The Handling package 95 5 1 Name space VscHandling 96 5 2 Handler 96 5 2 1 Constructor synopsis 97 5 2 2 Member synopsis 97 5 3 Telemetry Handler 98 5 3 1 Constructor synopsis 98 5 3 2 Member synopsis 98 5 4 Science Handler 98 5 4 1 Constructor synopsis 99 5 4 2 Member synopsis 99 5 5 Telecommand Handler 99 5 5 1 Constructor synopsis 99 5 5 2 Member synopsis 99 5 6 APID Range 99 5 6 1 Constructor synopsis 100 5 6 2 Member synopsis 100 5 7 Exceptions 101 Chapter 6 The Routing package 103 6 1 Name space VscRouting 104 6 2 Router 104 6 2 1 Constructor synopsis 105 6 2 2 Member synopsis 105 6 3 Telemetry Router 106 6 3 1 Constructor synopsis 106 6 3 2 Member synopsis 106 6 4 Science Router 106 6 4 1 Constructor synopsis 107 6 4 2 Member synopsis 107 6 5 Telecommand Router 107 6 5 1 Constructor synopsis 107 6 5 2 Member synopsis 107 6 6 Exceptions 108 6 6 1 Insufficient Memory 108 Chapter 7 The VSC proxy package 109 7 1 Name space VscProxy 110 7 2 Proxy 110 7 2 1 Constructor synopsis 112 7 2 2 Member synopsis 112 page 12 Initial public release The Virtual Spacecraft VSC Table of Contents Users Manual Version Issue 1 4 2 7 3 Scheduler control request 116 7 3 1 Constructor synopsis 116 7 3 2 Member synopsis 116 7 4 Control request 117 7 5 Cross strappi
39. C requires an absolute time it does so by accessing the observatory time base 1 3 1 1 Initializing the observatory time base In addition to the observatory time base the VSC also maintains a local or wall clock time base Both time bases are initilized whenever the VSC is booted First the wall clock time base is initialized Its initial value depends on the presence or absence of a GPS receiver within the VSC see Chapter 2 Ifa GPS receiver is present the time base is set to the current universal time as determined by the GPS receiver Ifa GPS receiver is not present the time base is set to the current universal time as determined by the local vxWorks real time clock see xxx Once the wall clock time base is established the observatory time base is simply initialized to the current value of the wall clock time base However at any time the base value of the observatory time base can also established via a request through the proxy interface see Section 7 4 The updated initial value depends on whether or not the request specifies a a particular value If a request specifies a particular time the time base will be set to that time 1 When the LAT is implemented within the testbed Initial public release page 29 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 Ifa request does not specify a particular time the don t care value the time base w
40. Enabling or disabling the interface corresponds to asserting or deasserting the DEVICE READY line of the interface see 7 If the interface was already enabled this operation has no effect Listing 29 Class definition for SsrInterface 1 class SsrInterface public Control 2 public 3 enum EnableDisable Enable Disable 4 public 5 SsrInterface EnableDisable Disable 6 public 7 Ssrinterface 8 public 9 EnableDisable state const 10 page 122 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 7 11 1 Constructor synopsis SsrInterface This constructor takes as an argument an enumeration see Section 7 11 which determines whether or not the interface is to be enabled or disabled This constructor throws no exceptions 7 11 2 Member synopsis state Returns the requested state expressed as an enumeration The member function has no arguments and throws no exceptions 7 12 Down load control request The function of this request is to be described Listing 30 Class definition for Download 1 class Download public Control 2 public constructors 3 Download unsigned short apid 4 public 5 Download 6 public 7 unsigned short apid const 8 unsigned long tid const 9 y 7 12 1 Constructor synopsis Download This constructor takes as an argument the APID of the teleme
41. Equation 2 converts BPU voltage sensor counts v to voltage V where v is the signed 16 bit ADC value and V is measured in volts V C C X Va where 2 Cy 200V c 4096counts B 1 3 BPU Current Bpul Equation 3 converts BPU current sensor counts v to current A where v is the signed 16 bit ADC value and A is measured in amperes A C C X Vy where 3 Cy 20A c 4096counts B 1 4 DAQ Current Daq l Equation 4 converts DAQ current sensor counts v to current A where v is the signed 16 bit ADC value and A is measured in amperes page 134 Initial public release The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring System Version Issue 1 4 2 A C C X Vy where 4 Cy 200A c 4096counts B 1 5 Thermistor Equation 5 converts thermistor sensor counts v to resistance r where v is the signed 16 bit ADC value and r is measured in kilo ohms The conversion from resistance to temperature is specified in reference 29 r Co V Cy where Cy 191488kQcounts 5 07 cy 120kQ B 1 6 RTD Equation 6 converts RTD sensor counts v to resistance r where v is the signed 16 bit ADC value and r is measured in kilo ohms The conversion from resistance to temperature is specified in reference 28 r Cote xv 0 03x v where Cy 775 5kQ c 0 097656kQ count 6 Cy 361 25 cz 0 049142 count
42. Ly 8 bool GBM_IN SSA 1 9 bool ARR_ENABLED Ly 10 unsigned int RESERVED 9 iis 12 enum GncMode Idle 0 13 Intertial_Capture ale 14 Sun_Point 2 15 Mission Interial_Point 3 16 Mission _Manuever 4 17 Mission Zenith Point 5 18 Reentry Cruise 6 19 Reentry Delta_V 7 20 public constructors 21 Data unsigned usecs 22 float POSITION X 234 float POSITION Y 24 float POSITION Z 254 float VELOCITY X 26 float VELOCITY Y 273 float VELOCITY Z 28 Data Gnc_Mode 29 unsigned SSR_USAGE 30 Data Flags 31 Data amp Data const Data 32 public destructor 33 Data 34 public 35 Data amp operator const Data amp 36 public 37 unsigned usecs const 38 public 39 float POSITION X const 40 float POSITION Y const 41 float POSITION Z const 42 float VELOCITY X const 43 float VELOCITY Y const 44 float VELOCITY Z const 45 Data GncMode GNC_MODE const 46 unsigned SSR_USAGE const 47 Data Flags FLAGS const 48 Initial public release page 91 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 4 11 1 Constructor synopsis Data This constructor builds an attitude ancillary GLAST telecommand as specified in 8 The first argument specifies the time within the execution period which the information contained in the packet was acquired This time is specified in micro seconds and may range from
43. O The GLAST experiment at SLAC The Virtual Spacecraft VSC GLAST Electronics group Users Manual Document Version Document Issue Document Edition Document Status Document ID Document Date 1 4 2 English Initial public release LAT TD 05601 December 5 2005 Stanford Linear Accelerator Center SLAC 2575 Sandhill Road Menlo Park California 94025 USA The Virtual Spacecraft VSC Users Manual December 5 2005 Version Issue 1 4 2 This document has been prepared using the Software Documentation Layout Templates that have been prepared by the IPT Group Information Process and Technology IT Division CERN The European Laboratory for Particle Physics For more information go to http framemaker cern ch page 2 Initial public release The Virtual Spacecraft VSC Users Manual Abstract Version Issue 1 4 2 Abstract A proposal for a SLAC produced version of the GLAST Spacecraft S C called the vsc Virtual Spacecraft The VSC consists of a VME crate containing modules which provide a complete implementation of the LAT to S C ICD including full redundancy and cross strapping support Within the crate resides the software necessary to control the interface to the LAT as well as software implementing an additional external interface This interface through TCP IP sockets allows an external application to interact with the VSC as if it were in the role of a ground station To do so the appl
44. Proxy Interface Instantiation Instantiation vsc diagnostic LAT diagnostic LAT telemetry vsc telemetry Science VSC Figure 19 Multiple proxy interfaces In this scenario the user on host A would connect as follows page 56 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 MyRouter router new MyRouter Proxy controlAndMonitor controlAndMonitor latDiagnostic router controlAndMonitor vscDiagnostic router While a user on host B would connect as follows MyRouter router new MyRouter Proxy processor processor latTelemetry router processor vscTelemetry router processor latScience router Note that independent of number of proxies instantiated or which proxies are connected to which telemetry streams each proxy retains a connection to the command stream and consequently the ability to command the vsc Therefore an application must be carefully crafted when apportioning control responsibilities in order to insure the two users do not conflict in the management of the VSC 3 2 Managing the SC GBM interface The GBM instrument s primary responsibility with respect to the LAT is notification of candidate GRBs Gamma Ray Burst As the GBM does not communicate directly with the LAT these alerts are relayed through the spacecra
45. SE 0 value and a FALSE deasserted logical value corresponds to a physical TRUE 1 value Listing 26 Class definition for ToggleLines 2 3 4 5 6 7 8 9 0 10 Tis class ToggleLines public Control public enum Lines Line0 0x1 Linel 0x2 Line2 0x4 public ToggleLines unsigned lines unsigned values public ToggleLines public unsigned lines const unsigned values const he 7 8 1 Constructor synopsis ToggleLines The first argument corresponds to a 3 bit mask which defines which of the three discrete lines are to be changed Each bit offset corresponds to a line If the bit at the corresponding offset is set the value of the line is to be changed If the bit at the offset is clear the line s value is left unchanged The new values of the discrete lines are determined by the second argument Each bit offset of this argument also corresponds to a discrete line If the bit at the corresponding offset is set and the corresponding offset in the first argument is set the discrete line is asserted If the bit at the corresponding offset is clear and the corresponding offset in the first argument is set the discrete is deasserted The class provides an enumeration for each of the bit offsets 7 8 2 Member synopsis lines values Returns the discrete lines to be changed Each bit offset corresponds to a line If the bit at the corresponding offset is set the value of
46. VSC as the time since the standard epoch 00 00 00 0 hours at January 1 2001 in seconds This function has no arguments and throws no exceptions If the request did not involve resetting the time base this function will return a value of zero 0 page 116 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 7 4 Control request All telecommands which provide direction to the VSC are called control requests In order to differentiate request based telecommands from GLAST based telecommands specific requests described below all sub class from Request Usage of this class is reserved to the implementation An application should never directly either use or sub class from Control It is documented in this chapter only for completeness Listing 23 Class definition for Control 1 class Control VscCcsds Telcmnd 2 Request unsigned short apid unsigned short function 3 public 4 Request 5 7 5 Cross strapping options In order to mitigate against single point failure both the VSC and LAT have redundant SIU and and DAQ communication interfaces All these interfaces are cross strapped and any change to the current cross strapping is governed by the request classes described in sections 7 6 and 7 7 Each of two classes takes as an argument the enumeration defined below enum Path AA 1 AB 2 BA 3 BB 4 T
47. ackage Users Manual Version Issue 1 4 2 by using the schedule function or may be stored for subsequent action or transmission at a specific time implicitly identified by using the scheduleAt function Down linked information is encoded as GLAST telemetry packets see Chapter 4 The application receives this telemetry by registering a router see Chapter 6 for each of the five asynchronous telemetry streams Listing 21 Class definition for Proxy 1 2 3 4 5z 6 7 8 ois 10 11 123 133 14 153 16 17 18 193 204 21l 223 233 24 25 26 27 28 29 30 31 32 33 34 35 36 class Proxy public Proxy Proxy Parameters amp public Proxy public void vscDiagnostic VscRouting void void void void public void latScience VscRouting S execute const Scheduler amp execute const Control amp execute const VscCcsds void void public void executeAt unsigned time void public void executeAt unsigned time schedule schedule const const const const const VscCcsds VscCcsds VscCcsds VscCcsds VscCcsds const VscCcsds const VscCcsds schedule unsigned time void void TelemetryRouters amp cienceRouter yi DE TeleCmnd amp const Control amp TeleCmnd const VscCcsds Attituder TimeTone amp Attitudes amp Attitudes amp Attitude amp Data amp Attitudex const con
48. ample period t Within the period are the twenty five slots numbered such that increasing slot number corresponds to increasing time relative to the period s start Associated with each slot is a potential telecommand to be sent by the VSC to the LAT see Section 1 4 3 4 For example slot nine 9 is offset 360 milliseconds from the beginning of the period persists until 400 milliseconds and is associated with the transmission of an ancillary attitude telecommand see Section 4 10 Spanning these twenty five slots scheduling involves five distinct phases sequenced as illustrated in Figure 7 0 1 24 harvest _ transit control command cleanup Figure 7 Phases within a period page 34 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 The activity within each of these phases is described below 1 4 3 1 Harvesting the work load During this phase each of the seven queues are probed for potential work If a queue is not empty the due field for the work request at the queue s head is examined The due field contains either zero 0 or an absolute time corresponding to the period in which the work contained within the entry should be performed A value of zero specifies the entry contains immediate work Immediate work independent of period is scheduled as soon as it appears A non zero value specifies the entry contains stored wor
49. and control the discrete interface between VSC and LAT define the scheduling of the seven different ancillary telecommands for each and every second of the VSC s operation See Chapter 7 for a detailed description of the classes of this package Each package is assigned its own individual chapter These chapter provide a detailed description of the classes contained within the package For example the VscCcsds package is described in chapter 4 1 2 1 Documentation conventions Each package is described individually in its appropriate chapter Each description starts with a synopsis of the package s function followed by a class dependency diagram expressing the Initial public release page 27 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 relationships between the classes of the package and the package s linkages to other classes in other packages The conventions for these diagrams are as follows Each box represents a class A shaded box indicates a class which is outside the package and on which at least one of the package s classes is dependent Arrows specify a relationship between classes A solid line specifies an inheritance relationship A dotted line specifies either a uses or a has a relationship The direction of the arrow is such that an arrow points away to the dependent class Following the class diagram is a description for
50. ansmission is not considered reliable the package must assure a mechanism to both catch and report both duplicate packets and incomplete datagrams The classes used to support datagram assembly are all based on the Assembler class described in Section A 2 The relationship between the classes of this package is illustrated in Figure A 1 ScienceHandler LciAssembler gt Assembler lt LpaAssembler y Dfi Datagram Figure A 1 Class dependencies for the datagram support package Initial public release page 127 The Virtual Spacecraft VSC Users Manual Appendix A The Datagram support package Version Issue 1 4 2 A 1 Name space VscDatagram A 2 Datagram Assembler This class which forms a base class for specific handlers described below is used to catch and assemble into datagrams incoming CCSDS science packets This class is derived from the canonical science handler see Section 4 8 As packets arrive to assemble the class triggers the validate method passing as an argument the incoming packet Once the datagram is assembled the dispose method is triggered This method receives as an argument both the assembled datagram and the number of packets which were used in its assembly The class retains state based on APID for any each pending assembly datagram As packets arrive they must satisfy the following constraints Their sequence flag
51. as a single wire in actual fact the wire represents communication between the three different types of physical interfaces between SIU and VSC These include i the 1553 interface ii the Discrete interface iii the Reset interface Therefore whenever the cross strapping is changed for one it s changed in unison for all three of these physical interfaces Each one of the four options corresponds to a particular path between the units as enumerated in Table 5 1 Which is from the viewpoint of the spacecraft a part of the discrete interface page 58 Initial public release The Virtual Spacecraft VSC Chapter 3 Using the proxy interface Users Manual Version Issue 1 4 2 Table 5 Cross strapping options for the siu interface Use Unit VSC LAT Path Primary Redundant Primary Redundant AA yes no yes no AB yes no no yes BA no yes yes no BB no yes no yes When the vsC is initially booted the VSC defaults to using the AA path which corresponds to using the Primary LAT interface communicating with the Primary SIU The SiulInterface request class see Section 7 6 is used to modify the current spacecraft LAT cross strapping The class s constructor takes as an argument an enumeration see Section 7 5 which specifies which one of the four cross strapping options should be selected For example to communicate with the redundant SIU through the vsc s redundant interfa
52. asses s constructor This method has no arguments and throws no exceptions GNC_MODE Returns an enumeration corresponding to the satellite s GNC mode This method has no arguments and throws no exceptions SSR_USAGE Returns a value which specifies the fraction of SSR storage used for science data not yet down linked This fraction is expressed as a number between zero 0 and 100 percent This method has no arguments and throws no exceptions FLAGS Returns a bit list representing the current state of the spacecraft See 7 for an explanation of the possible states This method has no arguments and throws no exceptions 4 12 The Time Tone Ancillary Telecommand Objects of this class are instantiated automatically by the VSC in response to processing a queued ancillary sequence see Section 7 2 This command indicates the exact time at the next transmission of the 1 PPS signal sent to the LAT see Section 1 3 Nominally this telecommand is sent to the LAT somewhere between 500 and 800 milliseconds before the corresponding 1 PPS signal is asserted The LAT s timing system uses both this telecommand and 1 PPS signal to establish its absolute time in a fashion which is coherent with the Spacecraft s absolute time Listing 11 Class definition for TimeTone 1 class TimeTone public M7Cmnd 2 public 3 public constructors 4 TimeTone bool sourceIsGps TRUE 5 TimeTone amp TimeTone const amp TimeTone 6 publ
53. at a user s application will be constructed A summary of the function of these packages would be VscCesds The quanta of information exchange between VSC and proxy interface is a CCSDS packet see 16 and 17 The observatory differentiates between two types of CCSDS packets telecommands and telemetry Telecommands are sent by the proxy interface to direct either the VSC or LAT to perform some generic type of action Telemetry is received from the VSC by the proxy interface and contains generic information about the state or health of either the VSC or LAT The CCSDS packet package contains a variety of classes to both instantiate and inspect CCSDS packets representing either telecommands or telemetry See Chapter 4 for a detailed description of the classes of this package 1 Unfortunately the usage of the word package in this context is quite distinct from its usage by CMX see Section 1 2 3 1 Although always received from the vsc telemetry may originate from either the VSC or the LAT page 26 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 VscHandlers This package provides the mechanisms to catch any arrived telemetry Telemetry arrives on three different streams the VSC telemetry LAT telemetry Science telemetry streams The application provides an individual handler for each stream This handler is used to catch and processes telemetry packet arrivin
54. atchall TS 0 public void route TG public const VscHandling Handler lt T gt head const const VscHandling Handler lt T gt last const public void insert VscHandling Handler lt T gt amp py 6 2 1 Constructor synopsis Router The constructor sets its internal list of handlers see Section 5 2 to empty This list corresponds to the set of handlers which the router is prepared to dispatch packets to If the list is empty the router will catch any packet independent of APID by calling back its cat chal1 method This constructor throws no exceptions 6 2 2 Member synopsis allocate route catchall This function is used to locate the memory to place an incoming CCSDS packet This function is always called before the appropriate handler is fired If memory cannot be allocated the derived class must throw the exception described in 6 6 1 The function returns a pointer to the allocated packet This method attempts to catch and process a particular incoming CCSDS packet This packet is represented by the input argument which is a reference to a CCSDS packet see Section 4 3 This involves traversing the routers s internal handler list checking for a handler to catch the packet If a handler is not found on the list the catchall method see below is invoked passing the caught packet as an argument This function returns no value and throws no exceptions This function is called by the rou
55. ation implementing the proxy interface may inter operate through the VSC with any representation of the LAT whether it s the real thing the testbed or a teststand This provides the user with a powerful tool to debug and commission their own applications As an example within Figure 1 the emulation of the LAT is the testbed residing in the DataFlow lab 1 1 Information Exchange Vertical arrows shown between entities in Figure 1 represents flow of information Information is exchanged between entities using a variety of protocols with the protocol page 22 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 varying on both the type of information exchanged and the information s latency and bandwidth requirements Therefore the information flow represented by a single arrow in Figure 1 can be further decomposed into a set of individual data streams as illustrated in Figure 2 PROXY INTERFACE VSC LAT LAT VSC science command diagnostic diagnostic telemetry telemetry telemetry VSC 1553 reset discretes science 1 PPS monitoring LAT Figure 2 Logical relationship of the VSC and its external interface to the observatory Each arrow represents not only the type of information exchanged on the stream but also that information on any one stream is exchanged asynchronously with respect to information exchange on any o
56. c virtual LpaAssembler de nu FF WN HP A 4 5 Constructor synopsis Just the default A 4 6 Member synopsis See the base class Section A 2 A 5 Exceptions none Initial public release page 131 The Virtual Spacecraft VSC Users Manual Appendix A The Datagram support package Version Issue 1 4 2 page 132 Initial public release The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring System Version Issue 1 4 2 Appendix B Telemetry from the Monitoring System The VSC monitors once per second 102 analog voltage current and temperatures from the LAT and its BPU Once acquired this information is transmitted from VSC to proxy as a series of CCSDS packets on the VSC telemetry stream see Section 7 2 Physically the monitored information originates from two different types of VSC boards the 850 and 468 board see Chapter 2 For each board the monitoring system generates a single packet with the packet s APID used to differentiate board In short 102 points are monitored and their information is spread over two type of packets giving a transmission rate of two packets per second This appendix describes for each type of packet the telemetry produced by the vSC s monitoring system These CCSDS packets follow the standard GLAST telemetry standards as described in Section 4 7 Section B 2 describes the telemetry packet produced by the 850 board and Section B
57. ce vsc execute Siulnterface BB Or to restore the cross strapping to its default setting vsc execute Siulnterface AA 3 3 2 SIU Reset The Reset request class see Section 7 9 is used to issue a LAT Reset as this fragment illustrates vsc execute Reset This reset signal is communicated to the LAT through whatever cross strapping is currently established see 3 3 1 Initial public release page 59 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 3 3 3 SIU discretes The ICD specifies three individual lines between the spacecraft and LAT which are driven by the spacecraft The spacecraft can either assert or deassert these lines When the VSC is initially booted the VSC interface deasserts the discrete lines The ToggleLines request class see Section 7 8 is used to toggle the state of the three discrete lines In a single request the interface may change the value of one two or three of these lines The first argument specifies the discrete lines to toggle and the second argument determines each line s new value Each bit offset of each argument corresponds to a particular line For example bit offset zero 0 corresponds to line zero Only if a bit offset in the first argument is set will the corresponding line s value be changed The new value of the line is determined by the corresponding bit offset in the secon
58. command called a control request see Section 7 4 Requests to the VSC originate from two different sources e From the Proxy through a network interface Requests are transmitted from the proxy up to the VSC through the command stream Requests arriving on the command stream are meant to provide direction either to the VSC or indirectly the LAT e From the LAT These requests arrive from the LAT through the 1553 interface Once requests arrive at the vsc the router based on request contents directs the request to its appropriate queue Initial public release page 31 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 1 4 2 Queuing Queues are used to buffer requests dispatched from the router Nominally the queue treats a request as a container holding a variable number of telecommands Each telecommand represents a quanta of work requested of the VSC The queue s principal responsibility is to decouple the rate at which the requests arrive with respect to the rate at which work as represented by the telecommands can be performed The queue serves the additional function of storing requests to be executed at a future specific time A queue contains two lists A pending and a free list Lists have FIFO discipline An entry on either list is a reference to a work request If a work request is on the pending list it represents work to be performed If a work request is on the free
59. d argument The ToggleLines class provides an enumeration for each of these offsets For example to deassert line zero 0 and to assert line two 2 while leaving line one 1 unchanged vsc execute ToggleLines Line0 Line2 Which one of the two sets of discrete lines primary or redundant actually toggled is determined by whatever cross strapping is currently established see 3 3 1 3 3 4 GASU DAQ board cross strapping The LAT has one GASU which contains two DAQ boards One DAQ board is designated as the Primary DAQ board and the other as the Redundant DAQ board Only one of the two DAQ boards is active at any one time In turn the spacecraft mitigates against single point failure by having two DAQ board interfaces which the VSC emulates One interface is called out as the Primary LAT interface and the other as the Redundant LAT interface In order to support full redundancy each of the four units has both an A and B port This results in the cross strapping of both interface and DAQ boards as illustrated by Figure 21 1 Actually four but the fourth is used as the LAT reset and is called out separately in Section 3 3 2 page 60 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 A E A Primary Primary DAQ LAT Interface A A Redundant 1 Redundant DAQ i i LAT Interface B EE Ga B
60. e Section 6 2 and satisfies the template argument with the class representing a telemetry packet see Section 4 3 Any application which routes telemetry packets is expected to sub class from TelemetryRouter and provide an implementation of both its allocate and catchall methods Listing 18 Class definition for TelemetryRouter T class TelemetryRouter public Router lt VscCcsds Telemetry gt 6 3 1 Constructor synopsis see Section 6 2 6 3 2 Member synopsis see Section 6 2 6 4 Science Router This class specifies a router for a science packets arriving on a science stream see Section 7 2 The implementation of this class simply derives from Router see Section 6 2 and satisfies the template argument with the class representing a science packet see Section 4 8 Any page 106 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 6 The Routing package Version Issue 1 4 2 application which routes science packets is expected to sub class from ScienceRouter and provide an implementation of both its allocate and catchall methods Listing 19 Class definition for ScienceRouter 1 class ScienceRouter public Router lt VscCcsds Science gt 6 4 1 Constructor synopsis see Section 6 2 6 4 2 Member synopsis see Section 6 2 6 5 Telecommand Router This class specifies a router for a telecommand packets arriving on a telecommand stream see Section 7 2 Th
61. e default size expressed as the maximum number of entries The sum of all work requests over all queues represent the work that the VSC is asked to both schedule and execute 1 4 3 Scheduling The scheduler is woken up periodically once per second Its principal responsibility is to both determine and then sequence any necessary work within each one second period The process requires the scheduler to break up each period into twenty five 40 milliseconds time slots as illustrated in Figure 6 Initial public release page 33 Users Manual The Virtual Spacecraft VSC Version Issue 1 4 2 Chapter 1 Introduction slot pe 1000 attitude 24 960 telecommand 22 yo telecommand 21 data 20 800 4 attitude 19 760 telecommand 17 680 s 4 telecommand 16 640 a telecommand 15 600 t ie i attitude 14 560 3 E TE telecommand 12 1 480 A i telecommand 11 440 i telecommand 10 400 attitude y telecommand telecommand time tone attitude telecommand telecommand telecommand 280 LN e ee 240 ae om A ge eG 0 EG te oy E E 080 10 1 ME pa Po 040 ea i e l fa Pe O NAUIONO No Q Q II OUUU UNI to ty ta ta A Figure 6 Scheduling within a period This figure shows the succession of periods labelled t ty etc and the structure of any one period for this ex
62. e ew 2 amp amp 28 1 3 Observatory time 4 2 4 28 we oe ww aoe amp 28 1 3 1 Time representation Ae we A es SI A 1 3 1 1 Initializing the Eset time base ea ss 29 1 3 2 Time Keeping gt e s s e wo k Co ok Gos i e Go SO Initial public release page 9 The Virtual Spacecraft VSC Table of Contents Users Manual Version Issue 1 4 2 1 4 Routing and scheduling requests 1 4 1 Routing 1 4 2 Queuing 1 4 3 Scheduling 1 4 3 1 Harvesting the T iid 1 4 3 2 Scheduling state transitions 1 4 3 3 Scheduling control work 1 4 3 4 Scheduling command work 1 4 3 5 Cleanup A 1 4 4 Scheduler State Model Chapter 2 Hardware 2 1 Electrical conventions 2 2 The SBC and 1553 interface 2 3 The GPS receiver 2 4 The Science interface 2 5 The Discrete interface 2 6 Digitizer i 2 7 LAT Cable eed 2 8 LAT Monitoring interface 2 9 VSC Configurations 2 9 1 The Testbed 2 10 VSC Inter Connectivity Chapter 3 Using the proxy interface 3 1 Distribution of telemetry ee 3 2 Managing the SC GBM interface 3 3 Managing the SC LAT interfaces 3 3 1 SIU cross strapping 3 3 2 SIU Reset 3 3 3 SIU discretes 3 3 4 GASU DAQ board cross epi 3 3 5 Enabling the Science Interface 3 3 6 Enabling Diagnostic Monitoring 3 4 Handling Incoming telemetry 3 4 1 APID filtering 3 5 Routing Incoming telemetry 3 5 1 Router registration 3 5 2 APID dispatching e 3 5 3 Science tele
63. e implementation of this class simply derives from Router see Section 6 2 and satisfies the template argument with the class representing a telecommand packet see Section 4 4 Any application which routes telecommand packets is expected to sub class from TeleCmndRouter and provide an implementation of both its allocate and catchall methods Listing 20 Class definition for TeleCmndRouter 1 class TeleCmndRouter public Router lt VscCcsds TeleCmnd gt 6 5 1 Constructor synopsis see Section 6 2 6 5 2 Member synopsis see Section 6 2 Initial public release page 107 The Virtual Spacecraft VSC Users Manual Chapter 6 The Routing package Version Issue 1 4 2 6 6 Exceptions 6 6 1 Insufficient Memory To be written page 108 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 Chapter 7 The VSC proxy package The VSC package consists of the classes which will form the anchor of any user application The classes contained within this package have four major functions i ii iii Provide a remote network passed connection to the VSC This is accomplished by instantiating the Proxy class Receive telemetry packets originating from both the LAT through the VSC and the vsc itself This is accomplished by registering telemetry routers see Chapter 6 using member functions of the Proxy class Command the vscC T
64. e monitoring of LAT analog voltage and temperature data see 7 When enabled monitoring information is sent on the vsc diagnostic stream see Section 7 2 as a series of CCSDS packets The number and structure of these packets are described in Appendix B Their are two identical monitors The Primary monitor and the Redundant Monitor Only one of these two monitors may be enabled at any one time By default when the VSC is started monitoring is disabled Initial public release page 121 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 Listing 28 Class definition for Monitor 1 class Monitor public Control 2 public 3 enum MonitorSide None Primary Redundant 4 public 5 Monitor MonitorSide None 6 public 7 Monitor 8 public 9 MonitorSide side const 10 y 7 10 1 Constructor synopsis Monitor This constructor takes as an argument an enumeration which determines whether or not monitoring is to be enabled or disabled If enabled the enumeration specifies whether to enable the Primary or Redundant monitor This constructor throws no exceptions 7 10 2 Member synopsis side Returns the requested monitor expressed as an enumeration The member function has no arguments and throws no exceptions 7 11 SSR control request The function of this request is to either enable or disable the reception of data through the SSR Interface
65. e scheduler The following code fragments provide one rather pedagogical example of how the VSC could be initialized First the necessary telemetry routers must be defined instantiated and registered with the proxy interface For example assume albeit unrealistically the router defined in Section 3 5 could be used to catch and process all incoming VSC and LAT telemetry Then to instantiate and register this router MyRouter router new MyRouter vsc latDiagnostic router vsc vscDiagnostic router vsc latTelemetry router vsc vscTelemetry router vsc latScience router Once registered the application must be prepared to catch and process telemetry Note that while VSC telemetry is inhibited with the scheduler stopped there is no such guarantee for LAT telemetry While highly unlikely that telemetry could flow out of the LAT and through the vsc with the scheduler stopped there is nothing in the VSC to actually prohibit such an action So if commanding or any other initilization should be live before telemetry is received the application could defer registration until the last step of initilization Next any LAT telecommands that the application wishes present before scheduling is started are queued For example assume before any user interaction with the LAT should be allowed the application requires assurance that the LAT s housekeeping system is in a well known state The LAT initializes the
66. ed In order to enable or disable monitoring one instantiates the Monitor class see Section 7 10 The argument to its constructor is an enumeration specifying which of two monitors to enable For example to enable monitoring from the Primary monitor vsc execute Monitoring Primary and to disable monitoring vsc execute Monitoring None Finally to enable monitoring from the Redundant monitor Initial public release page 63 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 vsc execute Monitoring Redundant Note When the VSC is initially booted monitoring is disabled 3 4 Handling Incoming telemetry In order to catch and process telemetry an application sub classes from one of two handlers described in chapter 5 TelemetryHandler ScienceHandler As an example imagine the construction of a set of tools to assist a user in debugging an application which processes telemetry One potentially useful tool would be a mechanism which simply decodes and prints the invariants associated with any CCSDS telemetry packet The following code fragment captures the spirit of this functionality void decode VscCcsds Telemetry amp packet const char title printf title printf Apid x and function x n packet apid packet function printf Acquired at d d n packet secs packet usecs
67. el VMESC5 from Systran Industries see xxx These boards digitize the 96 quantities sources by the LAT but monitored by the vsc A cable interface to the LAT This interface is a in house produced VME module called the VSCIO 850 This board is one of two cable interface modules see below between the VSC and LAT This particular module services all singles which either come from or go to the LAT shield This module has two functions It adapts the cabling from the shield to the flat ribbon cables required by the appropriate interface modules Initial public release page 41 The Virtual Spacecraft VSC Chapter 2 Hardware Users Manual Version Issue 1 4 2 2 1 Electrical conventions 2 2 The SBC and 1553 interface MVE2304 d HS Serial Port On d 100 Base T Ethernet 1553 o O gt 1553 B side lt x 1553 A side B TCLK Primary oa 05 wo CLK Redundant PEG Figure 9 SBC and 1553 interface page 42 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 2 Hardware Version Issue 1 4 2 2 3 The GPS receiver TTM637VMB GPS ANT O OER SYNOH SGNO9A4S SALANIN Figure 10 GPS receiver Initial public release page 43 The Virtual Spacecraft VSC Users Manual Chapter 2
68. ers are derived through a common base class see Section 5 2 as they all have exactly the same form except for the type of the packet they are intended to handle The user is expected to sub class from one of these three handlers in order to construct their own specific handler All handlers execute in the context of a specific thread see Section 3 5 1 The dependencies of the classes of this package are described in Figure 24 ScienceHandler gt Science Packet lt Handler TelemetryHandler gt Telemetry v AS ApidRange TeleCmndHandler gt TeleCmnd Figure 24 Class dependencies for the Handler package Initial public release page 95 The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 5 1 Name space VscHandling 5 2 Handler This class which forms a base class for the specific handlers described below is used to catch and process incoming CCSDS packets To catch a packet requires the derived class to specify a set of APIDs which the handler is willing to catch The handler maintains a list of APID ranges see Section 5 6 in order to determine which packets the handler will or will not handle To process a packet requires the derived class to provide an implementation of the abstract method process This method is passed as an argument the packet to
69. ery straightforward and requires only an instantiation of a Proxy object see Section 7 2 For example Proxy vsc If the Proxy class is successfully instantiated the application is successfully connected to the vsc Once connected the application controls the VSC by instantiating one or more requests or telecommands and then invoking the execute member of the Proxy class see Section 7 2 passing the request as an argument For example vsc execute Grb constructs an object which instructs the VSC to issue to the LAT a GRB Gamma Ray Burst alert Grb see Section 7 13 and then transmits this request to the VSC for later execution Note the VSC comes up in the stopped state see Section 1 4 and needs starting before any commands queued to the VSC are actually executed including the previous example However before starting the VSC a user typically needs to perform some application specific initilization While the form of this initilization is peculiar to each application most likely it would include the following steps for each type of telemetry define its router Initial public release page 53 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 define an appropriate set of telemetry handlers register an appropriate set of telemetry routers queue an initial set of LAT telecommands establish the vsc s time start th
70. es above could have been queued simultaneously vsc execute Scheduler Start SetTime T0 Reset 3 1 Distribution of telemetry The preceding example connects all five telemetry streams with one instantiation of the proxy interface on one host Schematically this scenario is represented by Figure 18 Initial public release page 55 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 Host A Proxy Interface Instantiation A vsc diagnostic LAT diagnostic LAT telemetry vsc telemetry Science VSC Figure 18 One proxy interface processing all telemetry streams However there is no necessity to register all streams with any one instantiation of the proxy interface For example diagnostic telemetry is considered real time and its prompt delivery may be useful to the robust operation of the VSC In such a case dividing the diagnostic telemetry from the housekeeping and science telemetry by directing the streams to two different proxies could be attractive One proxy would be responsible for the control and monitoring of the VSC and the other proxy responsible for processing any data delivered by the VSC An even greater isolation between these functions could be achieved by instantiating the proxies on separate hosts Such as scenario is represented in Figure 19 Host A Host B Proxy Interface
71. fer representing the data to be copied into the packet as the payload The second argument specifies the size of the payload data in bytes The size must be an even number of bytes The value of this argument must range from two 2 to the value returned by the maxPayload function described below This function returns no value and throws no exceptions function Returns the telcommand s function code This member function has no arguments and throws no exceptions maxPayload Returns the actual amount of storage reserved for a payload The current allocation of the payload is returned by the function described above This function has no arguments and throws no exceptions payload Returns a pointer to the payload portion of the corresponding CCSDS packet This function has no arguments and throws no exceptions sizeofPayload Returns the size in bytes of the payload portion of the corresponding CCSDS packet This function has no arguments and throws no exceptions recordedChecksum Returns the recorded payload check sum for the packet The computedChecksum function described below returns the computed checksum A properly formed packet has a computed checksum which is equal to its recorded checksum The recorded checksum is replaced each time the resizePayload function is called This function has no arguments and throws no exceptions computedChecksum Returns the computed payload check sum for the packet The recordedChecksum function descr
72. frame J This value was specified as an argument to the classes constructor This function has no arguments Qsu 4 Returns the scaler component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes constructor This function has no arguments WsJ_1 Returns the X axis component expressing the Spacecraft s S angular velocity Angular velocity is expressed in radians second This value was specified as an argument to the classes constructor This function has no arguments WSJ_2 Returns the Y axis component expressing the Spacecraft s S angular velocity Angular velocity is expressed in radians second This value was specified as an argument to the classes constructor This function has no arguments WsJ_3 Returns the Z axis component expressing the Spacecraft s S angular velocity Angular velocity is expressed in radians second This value was specified as an argument to the classes constructor This function has no arguments 4 11 The Ancillary Data Telecommand To be written page 90 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 Listing 10 Class definition for Data 1 class Data public M7Cmnd 2 public 3 struct Flags bool LAT_IN_SSA 1 4 bool IS_IN_ SUN 1 53 bool GPS_OUTAGE 1 6 bool SBAND_ON T 7 bool XBAND ON
73. from Handler see Section 5 2 and satisfies the template argument with the class representing a telecommand packet Any application which handles telecommand packets is expected to sub class from TeleCmndHandler and provide an implementation of its process method Listing 15 Class definition for TeleCmndHandler 1 class TeleCmndHandler public Handler lt VscCcsds TeleCmnd gt 5 5 1 Constructor synopsis see Section 5 2 5 5 2 Member synopsis see Section 5 2 5 6 APID Range This class captures the concept of an APID range The range is represented by two numbers one value specifying the lowest inclusive value of the range and the other specifying the inclusive highest value of the range If a range consists of a single number then both the low and high values of the range are equal If an incoming packet has an APID which falls within a range the packet is said to be catchable for that range A handler see Section 5 2 holds a list of APID ranges If any one of the ranges held by a handler would catch an incoming packet then the packet is said to be catchable by the handler Initial public release page 99 The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 Listing 16 Class definition for ApidRange 1 class ApidRange public VscList Link lt ApidRange gt 2 public constructors 33 ApidRange unsigned short 4 ApidRange unsigned short
74. ft When notified by the GBM the spacecraft sends an agreed upon signal to the LAT This interface allows an application to trigger the VSC to emit such a telecommand For example vsc execute Grb Initial public release page 57 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 3 3 Managing the SC LAT interfaces 3 3 1 SIU cross strapping The LAT has two SIUs Spacecraft Interface Unit One SIU is designated as the Primary SIU and the other as the Redundant SIU In orbit the redundant SIU is called out as a cold spare As the name implies SIUs interact with the spacecraft In turn the spacecraft mitigates against single point failure by having two SIU interfaces which the VSC emulates One interface is called out as the Primary LAT interface and the other as the Redundant LAT interface In order to support full redundancy each of the four units has both an A and B port This results in the cross strapping of both interface and SIU as illustrated by Figure 20 A HE E A Primary Primary SIU i LAT Interface B A A Redundant 1 1 Redundant LAT Interf SIU B mE 5 nterface LAT VSC Figure 20 siu cross strapping The figure illustrates that any one time the spacecraft uses one of its interfaces to communicate with one of the LAT s SIUs Note that while the figure shows any one communication path
75. g on that particular stream Each stream is associated with a separate thread see Section 3 5 It is in the context of that thread that the application s handler executes Chapter 5 contains a detailed description of the classes of this package VscProxy This package forms the anchor around which the application s implementation is built The package provides the following services Connects to the VSC commanding stream Allows an application to connect to any one of the five telemetry streams When connecting the application registers a handler to catch and process any and all telemetry packets arriving on the connected stream Allows the user to queue on the VSC any LAT telecommand for subsequent delivery and execution on the LAT Allows the user to queue on the VSC any VSC telecommand for latter delivery and execution on the vsc These telecommands construction and transmission are hidden behind another set of eight classes Each class groups together related telecommands into a single coherent interface The functions of these classes are to control the vsc s scheduler select and monitor SIU cross strapping select and monitor DAQ board cross strapping on the GASU control and monitor the FES Front End Simulator queue a GRB Gamma Ray Burst request to the LAT monitor and control the state of the device ready line of the science interface between VSC and LAT monitor
76. ge Version Issue 1 4 2 7 14 2 Member synopsis vse Returns the TCP IP host name of the VSC Note this function is virtual While there should be no necessity to do so if the host name agreement between VSC and proxy interface is broken the default assignment may be changed by over riding this function This function has no arguments and throws no exceptions control Returns the port number of the TCP IP port used to send outgoing CCSDS telecommand packets to the VSC These telecommands are handled internally by the VSC See the command function described below for the port number used to send telecommands which are relayed to the LAT Note this function is virtual While there should be no necessity to do so if the port number agreement between VSC and proxy interface is broken the default assignment may be changed by over riding this function This function has no arguments and throws no exceptions basePriority Returns the priority base used to establish the priority of the three different threads used to process incoming CCSDS telemetry packets see Section 7 2 The returned value may vary from zero 0 to 125 decimal with increasing priority corresponding to decreasing return value The relative priority between these three threads is fixed and cannot be changed however as this function is virtual it may be over ridden and the base priority re assigned 7 15 Exceptions 715 1 Data Stream Allocated To be written 7 15 2
77. he Virtual Spacecraft VSC Chapter 4 CCSDS package isPeriod Replaces the packet s current period value with the value specified by the argument Period time is represented as the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 This function returns the previous period value This function throws no exceptions 4 10 The Attitude Ancillary Telecommand To be written Listing 9 Class definition for Attitude 1 class Attitude public M7Cmnd 2 public constructors 3 Attitude unsigned usecs 4 double QSJ_1 5 double 0QSJ_2 6 double QSJ 3 7 double QSJ_ 4 8 float WSJ_1 93 float WSJ 2 10 float WSJ 3 11 Attitute amp Attitude const amp Attitude 12 public destructor 13 Attitude 14 public 15 Attitude amp operator const Attitude amp 16 public 17 unsigned usecs const 18 public 19 double QSJ_1 const 20 double QSJ_2 const 21 double QSJ_3 const 22 double QSJ_4 const 23 float WSJ_1 const 24 float WSJ_2 const 25 float WSJ_3 const 26 y 4 10 1 Constructor synopsis Attitude This constructor builds an attitude ancillary GLAST telecommand as specified in 8 The first argument specifies the time within the execution period to schedule the telecommand This time is specified in micro seconds and may range from a value of zero 0 to 999 999 decimal The next four arguments are quaternions which corresp
78. he classes s constructor This method has no arguments and throws no exceptions POSITION Y Returns the Y axis component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes s constructor This method has no arguments and throws no exceptions POSITION Z Returns the Z axis component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes s constructor This method has no arguments and throws no exceptions VELOCITY X Returns the X axis component of the quaternion expressing the velocity of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes s constructor This method has no arguments and throws no exceptions page 92 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 VELOCITY Y Returns the Y axis component of the quaternion expressing the velocity of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes s constructor This method has no arguments and throws no exceptions VELOCITY z Returns the Z axis component of the quaternion expressing the velocity of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the cl
79. he four units This request is used to specify which one of the four different cross strapping options should be used See Section 3 3 1 for more information Listing 25 Class definition for DaqInterface l class DaqInterface public Control 2 public 3 DagInterface VscProxy Path AA 4 public 5 DaqInterface 6 public 7 VscProxy Path path const 8 y 7 7 1 Constructor synopsis DagInterface This constructor takes as an argument the enumeration described in Section 7 5 This enumeration determines the exact cross strapping option requested If the argument is omitted the cross strapping request is equal to the initial cross strapping established by the vsc The constructor throws no exceptions 7 72 Member synopsis path Returns the enumeration described in Section 7 5 This enumeration specifies which one of the four cross strapping options is implied by the request This member has no arguments and throws no exceptions 78 SIU discrete control request The function of this request is change the state of one or more of the SIU s discrete lines Note This interface allows a discrete line to be either asserted or deasserted The definition of assertion follows the LAT negative logic convention where a TRUE asserted logical value corresponds to a Initial public release page 119 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 physical FAL
80. hin the payload of any one packet In other words the information spans packets Packet sequencing is not applicable for GLAST telecommands as they are fixed size 64 bytes and will always fit within a single packet However this is not necessarily true for GLAST telemetry In such a case the sequence flags and sequence number will working in conjunction identify what position in a sequence of information the packet occupies This position information is enumerated within Table 8 Table 8 Enumeration of sequence flag for a CCSDS telemetry packet Enumeration Value The packet is middle 0 part of a sequence but neither the first nor the last packet in the sequence first 1 the first packet of a sequence last 2 the last packet of a sequence alone 3 not part of a sequence These values are captured in the following enumeration Listing 1 Enumeration for packet sequence flags 1 enum SeqFlags middle 0 first 1 last 2 alone 3 4 3 Packet This class represents a generic CCSDS packet independent of whether the packet contains either telemetry or a telecommand An application never directly inherits from the class Instead this class is used indirectly through inheritance via the TeleCmnd and Telemetry classes see Section 4 4 and Section 4 6 Of course the class s member functions still interest an application These methods fit into three generic categories Header I
81. his enumeration specifies which one of the four cross strapping options should be applied as enumerated in Table 9 Table 9 Cross strapping options Use Unit VSC LAT Path Primary Redundant Primary Redundant AA yes no yes no AB yes no no yes BA no yes yes no BB no yes no yes Initial public release page 117 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 76 SIU interface control request The LAT has two SIUs Spacecraft Interface Unit One SIU is designated as the Primary SIU and the other as the Redundant SIU In orbit the redundant SIU is called out as a cold spare As the name implies SIUs interact with the spacecraft In turn the spacecraft mitigates against single point failure by having two SIU interfaces which the VSC emulates One interface is called out as the Primary LAT interface and the other as the Redundant LAT interface In order to support full redundancy each of the four units has both an A and B port The SIUs and VSC interfaces are physically cross strapped in order to allow mixing and matching of the four units This request is used to specify which one of the four different cross strapping options should be used See Section 3 3 1 for more information Listing 24 Class definition for SiuInterface 1 class SiuInterface public Control 2 public 3 SiuInterface VscProxy Path AA 4 public 5 Si
82. his is accomplished by calling member functions of the Proxy class passing as arguments specific request telecommands to be queued to and executed by the vsc All request telecommands inherit from the Request class The bulk of the classes described in this chapter are request telecommands Command the LAT This is accomplished by calling member functions of the Proxy class passing as arguments LAT specific telecommands to be queued to the VSC for subsequent transmission over its 1553 interface to the LAT Initial public release page 109 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 Scheduler gt StartPauseStop V Reset Parameters gt TeleCmnd x 7 m ToggleLines Proxy 7 gt Control p Download gt Attitude Ssrinterface gt EnableDisable TelemetryRouter lt T ad TimeTone Monitor 3 MonitorSide ScienceRouter lt 72 Data Siulnterface i ExPort lt SA Path gt TeleCmnd Daqinterface aI Grb Figure 26 Class dependencies for the proxy package 7 1 Name space VscProxy 7 2 Proxy The Proxy class provides a remote network based interface to the functionality of the VSC The network pro
83. housekeeping system in response to a SYSRET telecommand A class representation of this telecommand is defined in Section 3 6 Therefore to initialize housekeeping one simply instantiates this class invokes the execute member of the proxy interface passing as an argument the instantiated telecommand vsc execute SysReset The execute member transmits the specified telecommand to the VSC where it is routed to its appropriate queue for execution at the time until the scheduler is started Once the VSC is started see below the telecommand is then set to the LAT through its 1553 interface Note the execute function is synchronous the function does not return to the caller until the command has either been safely transmitted to the VSC or an exception has been thrown The next step in the initialization requires the setting the absolute time for the VSC and consequently the LAT page 54 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 define TO unsigned OxDEADBEEF vsc execute SetTime TO Need some more explanation here Next the scheduler and the vsc s clock is started vsc execute Scheduler Start Finally the LAT itself is reset vsc execute Reset Note that because the VSC allows more then one command to be executed each period the three commands of the exampl
84. ibed above returns the recorded checksum A properly formed packet has a computed checksum which is equal to its recorded checksum This function has no arguments and throws no exceptions 4 5 Mangle This class is used to consciously mangle the format and structure of a GLAST telecommand Nominally of course there would seem to be no need to purposely construct and transmit an ill formed telecommand The express reason for this class s existence is to test the LAT s response to invalid telecommands When for a particular application this reason does not exist its safe to assume the application can afford to ignore this class The class consists of a number of virtual functions each function corresponding to a field of a telecommand which may be mangled Each function returns a mangled value for its corresponding field Because the functions are virtual they may be over loaded allowing application to customize both the fields which should be mangled and their respective values In practice mangling is accomplished by instantiating either the class or a class derived from it and then passing the resulting object as an argument to Tel eCmnd s constructor see page 82 Initial public release The Virtual Spacecraft VSC Chapter 4 CCSDS package Users Manual Version Issue 1 4 2 Section 4 4 Note that by default that is using the base class without derivation each member returns a value guaranteed to be inappropriate
85. ic destructor 7 virtual TimeTone 8 public 9 TimeTone amp operator const TimeTone amp 10 public 11 bool sourceIsGps const 12 unsigned timelIs const 13 y Initial public release page 93 The Virtual Spacecraft VSC Chapter 4 CCSDS package Users Manual Version Issue 1 4 2 4 12 1 Constructor synopsis TimeTone This constructor builds a so called time tone ancillary GLAST telecommand as specified in 8 The first argument specifies both the execution time of the telecommand and the and the exact time corresponding to the next transmission of the 1 PPS signal sent to the LAT As these two values are the same there is no specific access to this field however its value can be retrieved by calling the execution time function associated with the telecommand see Section 4 4 The second argument is a boolean specifying whether or not the time indicated by the command was synchronized by the VSC s GPS system If not synchronized time was derived by a local clock whose stability with respect to the 1 PPs signal is not guaranteed The default option specifies that the time was derived through GPS Ancillary telecommands are transmitted for execution by objects of the class described in Section 7 2 This constructor throws no exceptions 4 12 2 Member synopsis sourcelsGps Returns a boolean specifying whether the time indicated by the command timels was synchronized by the VSC s GPS
86. ication codes against a set of C classes called the Proxy Interface A complete description and explanation of these classes is one of the principal goals of this document Intended audience While a design proposal this document is intended principally as a guide for the users of the vsc These include e Testers of Flight Software e Developers of Flight Software e Developers of I amp T Integration and Test based systems Conventions used in this document Certain special typographical conventions are used in this document They are documented here for the convenience of the reader e Field names are shown in bold and italics e g respond or parity e Acronyms are shown in small caps e g SLAC or TEM e Hardware signal or register names are shown in Courier bold e g RIGHT_FIRST or LAYER MASK 1 Initial public release page 3 The Virtual Spacecraft VSC References Users Manual Version Issue 1 4 2 References 1 1553 Product Handbook United Technologies Microelectronics Center Inc 1992 2 CCSDS Package User Manual LAT Flight Software User Manual 3 CTDB 1553 Drivers LAT Flight Software User Manual 4 EGSE Used to Test GASU LAT TD05787 5 Enhanced Summit Family Product Handbook UTMC Microelectronics Systems Inc October 1999 6 GLAST 1553 Bus Protocol Interface Control Document Spectrum Astro Inc 7 GLAST LAT Instrument Spacecraft Interface Requirements Document 433 IRD 0001 Revision
87. ication provides the proxy interface with a router A router is an application specific class inheriting from Router contained in the Routing package described in Chapter 6 Once instantiated a router is registered with the proxy interface Once registered the router is invoked by the proxy interface for each arriving CCSDS packet There are four steps involved in constructing an application specific router page 66 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 i Sub class from the router base class ii Implement memory management strategy for arriving packets If the processing of the packet can take processed entirely within the context of the router memory for only one packet is necessary If the processing of the packet is delegated to other processes perhaps executing in a different thread then a scheme where packets are allocated and deallocated from free store may be necessary iii Specify the set of necessary packet handlers iv Implement a catchall This is a handler to designed to catch any packets which were not caught by the specified set of packet handlers As an example suppose a router is specified which process packets entirely in its own context This implies a fixed packet allocation scheme is sufficient If this router s name is MyRouter its class definition would be as follows class MyRouter public Telemet
88. ill be set to the current value of the wall clock time base Note that whatever the mechanisms the time base is established booting or requested the the VSC scheduler must be in the stopped state see Section 1 4 3 Setting an explicit time allows the VSC s time to be consistent with for example a physics simulation which drives the LAT through the FES 1 3 2 Time Keeping Both the VSC and LAT are slaved to a hardware generated 1 PPS One Pulse Per Second signal The presence or absence of a GPS receiver see Chapter 2 determines which one of two types of 1 PPS signal is used A stable source A 1 PPS signal derived by VME based GPS receiver In turn The GPS receiver may derive its timing externally from satellite or internally fly wheel A degraded source A 1 PPS signal derived from a clock driven by the vsC s science interface see Chapter 2 On boot the VSC chooses for its 1 PPS signal the most stable source available The 1 PPS signal has four functions i re synchronizes the wall clock ii increments the observatory time base iii triggers the VSC s scheduler see Section 1 4 iv is transmitted to the LAT Shortly before the 1 PPS signal is transmitted to the LAT the VSC generates the so called time tone telecommand see Section 4 12 This command announces the observatory time for corresponding 1 PPS signal This telecommand is one of the seven ancillary commands sent once a second to the LAT
89. ilure each quantity is brought to the spacecraft from the LAT twice therefore in actuality this corresponds to monitoring 184 quantities The spacecraft has block redundancy with one set of signals the primary signals being monitored by one monitor and the other set the redundant signals being monitored by another At any one time only a single set of signals are acquired and sent to the ground As the VSC emulates the spacecraft it must provide analogous functionality In addition to support ground operations the VSC must also monitor 10 different voltages and currents from the BPU Both these functions are provided by the so called monitor interface Physically this information is brought from the LAT to the VSC page 62 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 through the vsc s 850 and 468 boards see Chapter 2 Once brought to the VSC these data are digitized by the VSC s Systran boards see Chapter 2 The monitor software on the VSC periodically once a second reads these digitized temperatures and voltages packages them up as a set of CCSDS telemetry packets and sends these packets down to the proxy through its vsc diagnostic stream see Section 7 2 The monitor has two components the primary monitor and the redundant monitor The user must select which one of these two monitors will be used to collect this telemetry Once this telemetry ar
90. in Section 1 4 The arguments following the first argument are references to a series of objects Each object corresponds to a command request sent as a telecommand see Section 4 4 to be executed by the VSC within the scheduled one second period This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 executeAt unsigned time TeleCmnd Transmitsa set of up to eight 8 commands on the command stream to the VSC where these telecommands are then queued on the VSC for subsequent transmission to the LAT at a time within a specific one second period The period is specified by the first argument whose value represents the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 The commands transmitted are represented by the arguments following the period first argument Relative to each other these commands are transmitted to page 114 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 the LAT in argument order The relative time structure between these and other telecommands transmitted to the LAT is discussed in Section 1 4 The arguments following the first argument are references to a series of objects Each object corresponds to a telecommand see Section 4 4 to be sent to the LAT within the scheduled one second period This function returns no value This functi
91. ion The only difference being the printing of the header string proceeding the decode function To actually dispatch arriving telemetry the router must be both instantiated and registered This process is described in the next section 3 5 1 Router registration Telemetry is delivered by the proxy interface on five asynchronous streams That implies telemetry on any one stream arrives both unsolicited and independently with respect to telemetry on any other stream The proxy interface dispatches telemetry to an application through a router see Section 3 5 The application creates the router and registers the router with the proxy by calling an appropriate method of the Proxy class see Section 7 2 The correspondence between stream and registration method is enumerated in Table 7 For example to catch telemetry on the LAT telemetry stream the application would register their router by invoking the lat Telemetry function of the Proxy class passing to the function as an argument the router to be registered Table 7 Streams and registration methods Stream Registration Method vsc diagnostic vscDiagnostic LAT diagnostic latDiagnostic VSC telemetry vscTelemetry LAT telemetry latTelemetry Science telemetry latScience The proxy interface associates a thread with each stream The execution code represented by an application s router and its set of handlers is all executed in the context of that thread The
92. is maintained on the VSC This is a predefined set of analog voltage and temperatures on the LAT but measured by the vsc The VSC uses these measurements as input into the decision to power on and boot the LAT The measurement of these temperatures and voltage are not part of the LAT s housekeeping telemetry as they must be monitored even when the LAT is not operating Instead this information is sent as VSC telemetry see appendix B 1 1 2 Information Exchange between VSC and proxy interface command This stream transmits CCSDS telecommands from the proxy interface to the VSC Telecommands fit into two classes Control requests and Commands Control Requests are telecommands consumed entirely within the VSC and generally constitute the functions to manage and control the VSC and its interfaces to the LAT One example of a request would be the telecommand used to establish which of two SIU s primary or redundant the VSC communicates with on the LAT The set of telecommands which are allowed on this stream are enumerated and described in xxx Commands are telecommands whose final destination is the LAT These commands are queued on the VSC for later delivery to the LAT The set of commands allowed on this stream is enumerated and described within the The GLAST Command and Telemetry Database see 18 page 24 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2
93. k If this value is non zero it is compared to the period s time If equal the work contained within the entry should be scheduled In short from the scheduler s perspective harvesting consists of requesting from the queue its list of work for that period The work list is a series of telecommands each telecommand representing one quanta of work Therefore at the end of harvesting the scheduler has seven different work lists one for each queue If the queue does not have any work for the specified period its work list will be empty This phase is the first activity within slot zero 0 1 4 3 2 Scheduling state transitions During this phase the scheduler attempts to process the telecommands on the work list associated with the transition queue see Table 4 The scheduler s behaviour is modelled as a Finite State Machine FSM The states and transitions of this machine are discussed in Section 1 4 4 The events which trigger state transitions correspond to the telecommands on this work list Therefore during this phase the scheduler transits to a potentially new state consistent with its current state and the presence of any transition events Once this phase completes if the scheduler is left in either the paused or stopped state the remainder of the phases discussed below are not executed This phase occurs within slot zero 0 1 4 3 3 Scheduling control work During this phase the scheduler attempts to process the telecommands on
94. lease page 21 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 spacecraft then the application coded against the proxy interface would represent a simulation of the ground station Because the proxy interface is a programmatic interface a variety of ground station simulations could be envisioned For example ground stations whose client is e FSW and FSW Test in order to both develop and test the LAT s flight software system e I amp T LATTE 5 in order to manage the integration and test of the instrument e The ISOC in order to both develop and test the instrument s ground station The relationship between the role of the VSC its proxy interface the Spacecraft LAT and ground station is illustrated in Figure 1 emulation of ground station lt LATTE 5 PROXY INTERFACE Back End Interface emulation of spacecraft lt VSC Front End Interface a 3 Back End Interface emulation of LAT TESTBED Figure 1 Logical relationship of the VSC and its proxy interface to the observatory Where here as one example the emulation of the ground station is LATTE 5 Recall the LAT itself represents an abstraction This abstraction is realized in many forms three examples are the test stand the test bed and of course the physical realization of the real LAT Therefore any applic
95. legitimate LCI datagrams Note Because the APIDs produced by the LCI system are both fixed and determined by FSW the user calls the base class s handle method see Section 5 2 at their own peril The definition for this class is contained in Listing A 2 Listing A 2 Class definition for LciAssembler virtual LciAssembler 1 class LciAssembler public Assembler 2 3 public 3 LciAssembler 4 public 5 6 A 3 3 Constructor synopsis Just the default A 3 4 Member synopsis See the base class Section A 2 A 4 LPA Assembler This class allows for the assembly of datagrams which originated from FSW s LAT Physics Analysis LPA system see 25 The implementation of this class is straightforward itinherits from Assembler see Section A 2 determines and sets the maximum size of any expected datagrams page 130 Initial public release The Virtual Spacecraft VSC Users Manual Appendix A The Datagram support package Version Issue 1 4 2 determines and registers the APIDs corresponding to legitimate LPA datagrams Note Because the APIDs produced by the LPA system are both fixed and determined by FSW the user calls the base class s handle method see Section 5 2 at their own peril The definition for this class is contained in Listing A 3 Listing A 3 Class definition for LpaAssembler class LpaAssembler public Assembler public LpaAssembler publi
96. lemetry Start by reusing the HoueseKeeping class Next define a new handler called Alert class Alert public MyHandler public Alert Alert For clarity Alert has almost the exact implementation as Houeskeeping In substance it differs only in its constructor implementation Alert Alert MyHandler Alert range 0x340 0x39F with the implementation varying in the alert APID range and title string A real example would of course take a very different form Finally modify MyRouter s constructor and register two handlers MyRouter MyRouter _dump Unexpected packet insert new Alert insert new Houskekeeping 1 But in this case we limit the handler to process only housekeeping APIDs Initial public release page 69 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 3 5 3 Science telemetry and datagrams To be written At this point there are still some ambiguities about the structure of the science data which I m trying to resolve Stay tuned 3 6 Telecommands Control of the LAT through the VSC is exercised by queuing telecommands to the VSC Telecommands are CCSDS packets which include a GLAST specific secondary header see 8 This structure is captured by the TeleCmnd class described in Section 4 4 which is part of the data ha
97. lic release page 85 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 4 6 2 Member synopsis copy Copies the data specified by the argument into the payload of the packet Any data currently in the payload is lost The first argument is a pointer to a buffer representing the data to be copied into the packet as the payload The second argument specifies the size of the payload data in bytes The size must be an even number of bytes The value of this argument must range from two 2 to the value returned by the maxPayload function described below This function returns no value and throws no exceptions append Appends the data specified by the argument into the payload of the packet The first argument is a pointer to a buffer representing the data to be appended to the current payload The second argument specifies the size of the appended data in bytes The size must be an even number of bytes The value of this argument must be no larger then the difference between the values returned by the sizeofPayload and the maxPayload functions If so the remainder is simply not copied This function returns no value and throws no exceptions payload Returns a pointer to the payload portion of the corresponding CCSDS packet This function has no arguments and throws no exceptions sizeofPayload Returns the size in bytes of the payload portion of the corresponding CCSDS packet This function has no argument
98. list it is available as a template from which to form a pending work request The work request contains a variable number of telecommands up to some predefined maximum A work request also specifies the time at which the actions represented by the set of telecommands are to be executed Execution time is specified using GLAST standard convention where time is represented as the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 The relationship between list and work request is illustrated in Figure 5 execution time of commands gt head free list telecommandy router triggers scheduler triggers telecommand telecommand gt head lt pending list telecommand 4 telecommand pending work request Figure 5 vsc queue both immediate and stored The life cycle of a work request is basically as follows when a request telecommand from the router arrives a work request is removed from the head of the free list the contents of the router s request copied to the work request and the work request inserted at the tail of the 1 With the exception of LAT based requests which originate through the 1553 interface page 32 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduc
99. lot is left empty Ifthe slot specifies an generic command the telecommand at the head of the work list associated with the stored command queue is removed and transmitted If when removing a command from this list the list is empty the telecommand at the head of the work list associated with the immediate command queue is removed and transmitted If when removing a command from this list the list is empty the slot is left unfilled This phase occurs on slots zero 0 through slot twenty four 24 1 4 3 5 Cleanup This phase occurs after all the work scheduled for this period is performed In this phase the work requested of the period is compared with the work performed within the period When the two are equal the resources required to perform the work are recovered In detail this involves asking each of the six queues to examine the work list for the work request at the head of its pending list If the work list is empty the work request is removed from the queue s pending list and returned to its free list This phase occurs on the last slot 24 1 They are reserved to the 1553 hardware driver to solicit telemetry from the LAT page 36 Initial public release The Virtual Spacecraft VSC Chapter 1 Introduction Users Manual Version Issue 1 4 2 1 4 4 Scheduler State Model The scheduler has abstract behaviour For example it can be started or stopped This behaviour is modelled as a Finite State Machine
100. low unsigned short high 5 public 6 ApidRange T public 8 const ApidRange amp next const 9 public 10 unsigned short low const 11 unsigned short high const 12 y 5 6 1 Constructor synopsis ApidRange unsigned short low The constructor assigns the argument as the APID corresponding to both the low and high value of the range By convention this implies the range spans a single APID The constructor throws no exceptions ApidRange unsigned short low unsigned short high The constructor assigns the smaller of the two arguments as the APID corresponding to the low value of the range The larger of the two arguments is assigned as the APID corresponding to the high range For good style the first argument should correspond to the smaller value and the second the larger value The constructor throws no exceptions 5 6 2 Member synopsis next If this range resides on a handler s range list see Section 5 2 this method returns a reference to the range on the list following this range If the range is not on a list the method returns a reference to itself If the range is at the list s tail it returns a reference which is equal to the list itself This function throws no exceptions low This function returns the smaller of the two APIDs specifying the range If the range s extent corresponds to only one APID the value returned will be equal to the returned value of the high function described below This
101. mal digits The hexadecimal digits are the digits 0 through 9 plus the characters a through or A through F which have the values 10 through 15 respectively For example a queue size of twenty nine could be expressed as either 29 0X1D or 0x1d For example to change the size of the Ancillary queue the signature of the init_vsc procedure could be as follows init _vse Ancillary 1000000 This would create an Ancillary queue capable of buffering up to one million decimal seconds worth of ancillary sequences and the other five queues would retain their default values If one the other hand two queues required new values init_vsc Ancillary 1000000 CommandStored 0x1F 3 8 2 Network configuration 3 8 2 1 VSC node name and IP address To be written 1 One entry on the ancillary queue holds all seven ancillary commands Initial public release page 75 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 3 8 2 2 Port Numbers To be written page 76 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 Chapter 4 CCSDS package The principal quanta of information between the VSC and the LAT and consequently the principal quanta of information between VSC and application is the CCSDS packet see 16 and 17 This package contains the necessary class sup
102. mary SIU Spare Voltage hermistor Redundant SIU Temperature Redundant SIU Spare Temperature edundant SIU Spare Voltage rimary GASU DAQ Board Temperature imary GASU DAQ Board Converter AEM EBM Digital Voltage 3 3V rimary GASU DAQ Board Converter AEM EBM Digital Voltage 2 5V rimary GASU DAQ Board Converter CRU GEM Digital Voltage 3 3V LatV hermistor Primary GASU DAQ Board Spare Temperature LatV timary GASU DAQ Board Spare Voltage 1 LatV rimary GASU DAQ Board Spare Voltage 2 hermistor Redundant GASU DAQ Board Temperature LatV Redundant GASU DAQ Board Converter AEM EBM Digital Voltage 3 3V LatV Redundant GASU DAQ Board Converter AEM EBM Digital Voltage 2 5V LatV Redundant GASU DAQ Board Converter CRU GEM Digital Voltage 3 3V LatV Redundant GASU DAQ Board Converter CRU GEM Digital Voltage 2 5V hermistor Redundant GASU DAQ Board Spare Temperature LatV Redundant GASU DAQ Board Spare Voltage 1 LatV edundant GASU DAQ Board Spare Voltage 2 hermistor La hermistor Lat La LaWV LatV pul pul pu pu pul pu pul pu pul A Which SC monitor was used to generate this packet hermistor hermistor Es hl PPP Q lt o 5 2 n lt fN D O o TU gt 4 po alkaa gt Ul U U U w w Figure B 1 Enumeration of 850 board monitored quantities Initial public release page 137 The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring Sys
103. metry and datagrams 3 6 Telecommands 30 31 32 33 35 35 35 36 36 37 41 42 42 43 44 45 46 46 47 48 48 51 53 55 57 58 58 59 60 60 62 62 64 65 66 68 69 70 70 page 10 Initial public release The Virtual Spacecraft VSC Table of Contents Users Manual Version Issue 1 4 2 3 7 Scheduling the Magic seven 71 3 8 Administrating the VSC 74 3 8 1 Configuring queue sizes 74 3 8 2 Network configuration 75 3 8 2 1 VSC node name and IP ddr 75 3 8 2 2 Port Numbers 76 Chapter 4 CCSDS package 77 4 1 Name space VscCcsds 78 4 2 Packet sequencing 78 4 3 Packet T 78 4 3 1 Constructor synopsis 79 4 3 2 Member synopsis 80 4 4 TeleCmnd 80 4 4 1 Constructor synopsis 81 4 4 2 Member synopsis 82 4 5 Mangle 82 4 5 1 Constructor synopsis 83 4 5 2 Member synopsis 83 4 6 Generic Telemetry packet 84 4 6 1 Constructor synopsis 85 4 6 2 Member synopsis 86 4 7 Telemetry 86 4 8 Science 87 4 8 1 Member synopsis 87 4 9 The Magic 7 Telecommands 88 4 9 1 Constructor synopsis 88 4 9 2 Member synopsis 88 4 10 The Attitude Ancillary ome 89 4 10 1 Constructor synopsis 89 4 10 2 Member synopsis 90 4 11 The Ancillary Data Telecommand 90 4 11 1 Constructor synopsis 92 4 11 2 Member synopsis 92 4 12 The Time Tone Ancillary Telecommand 93 4 12 1 Constructor synopsis 94 4 12 2 Member synopsis 94 4 13 Exceptions 94 Chapter 5 Initial public release page 11 The Virtual Spacecraft VS
104. n 4 10 one contains miscellaneous data Initial public release page 71 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 Section 4 11 and one contains the timetone for the subsequent 1 PPS signal see Section 4 12 Within each one second period these commands are sequenced and scheduled in a predefined order as specified in 8 and discussed in Section 1 4 3 The pertinent details for ancillary sequencing are as follows The scheduler divides each one second period into twenty five fixed time slots of 40000 microseconds each As the spacecraft limits transmission to at most one command per slot only one of the magic seven is sent within any one slot The ICD calls out a specific time slot for each of the magic seven commands If one assumes that t represents the VSC s initial observatory time base see Section 1 3 Figure 22 illustrates the scheduling process 1000000 attitude 24 960000 data 20 800000 attitude 19 760000 attitude 14 560000 attitude 9 360000 o Pi time tone 5 200000 i i o i attitude 4 160000 i i a slot a io 000000 A i l uA NI gt LALA to t tp t3 th Figure 22 Scheduling the Magic seven For example when requested the timetone command is always transmitted by the VSC somewhere within slot five
105. n of the modules are VME modules and the eighth is a PMC card These modules are i ii iii iv vi vii A commercial Single Board Computer SBC The SBC is a VME module model Motorola MVE2304 see xxx The 2304 serves two functions First as the platform under which the software of the VSC executes see chapter 3 and second as the carrier for the 1553 PMC cards see below A commercial 1553 interface The 1553 interface is a model PMC 1553B from Alphi Technologies see xxx This interface is on a PMC form factor and resides in the SBC described above A fully populated VSC contains two of these interfaces One serving as the primary 1553 interface and the second as the redundant 1553 interface A commercial GPS receiver The GPS receiver is a VME module model TTM637VME from Symmetricom Industries see xxx This module serves as the time base for the vsc and consequently for the LAT when it is attached to the VSC A Science interface This interface is a in house produced VME module called the VSC SCI A fully populated VSC contains two of these modules One serving as the Primary science interface and the second as the Redundant science interface A Discrete interface This interface is a in house produced VME module called the VSC DSC A single module implements both the primary and redundant discrete interfaces One or more commercial digitizer boards The digitizer board is an industry standard I O pack mod
106. nction has no arguments and throws no exceptions This class specifies a GLAST specific CCSDS telecommand packet All GLAST telecommands share a common set of attributes In particular the isTelecommand function always returns TRUE The sequence flag field is always set to alone page 80 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 telecommands have a fixed size which is 64 bytes independent of the number of significant bytes in the payload That is the maxPayload function will return 64 bytes less the header A payload checksum This checksum is always located at the end of the allocated payload Each time the payload is copied the checksum is re computed A example of how an application constructs their own telecommands is found in Section 3 6 Listing 3 Class definition for TeleCmnd 1 class TeleCmnd public Packet lt 64 gt 2 public constructors 3 TeleCmnd unsigned short apid 0 unsigned short function 0 4 TeleCmnd const Mangle amp short apid 0 short function 0 5 TeleCmnd const TelCmnd amp 6 public 7 TeleCmnd 8 public 9 TeleCmnd amp operator const TeleCmnd amp 10 public 11 void copy const void int sizeofPayload 12 public 13 unsigned short function const 14 unsigned short maxPayload const I5 const unsigned short payload const 16 public 17
107. ndling package While all telecommands share the same shape they all differ in their respective payloads This means in practice for most applications specific telecommands are constructed by derivation using TeleCmnd as a base class The customization of these classes typically will involve additional constructors and access methods For example consider an implementation of the LAT specific telcommand SysReset see 18 This command resets the LAT s housekeeping system using a specified set of configuration files The parameters for this telecommand packet are as follows The APIDis 650 hexadecimal The function code is one 1 The payload contains one four 4 element array Each element of the array is an unsigned 32 bit value which specifies a configuration file ID These parameters can be summarized with two defines and one structure struct MyPayload unsigned filelds 4 define APID 0x0650 define FUNCTION 1 First the class definition which is named after the telecommand mnemonic The IDs for configurations files will be specified as arguments to the constructor The number of configuration files can actually vary from zero to four which implies four constructors For pedagogical reasons only the first few constructors are shown in the definition In order to access the file IDs the class has four methods the name of the method corresponding to the corresponding file ID passed in the construct
108. ng options 117 7 6 SIU interface control request 118 7 6 1 Constructor synopsis 118 7 6 2 Member synopsis 118 7 7 DAQ interface control request 118 7 7 1 Constructor synopsis 119 7 7 2 Member synopsis 119 7 8 SIU discrete control request 119 7 8 1 Constructor synopsis 120 7 8 2 Member synopsis 120 7 9 SIU reset control request 121 7 9 1 Constructor synopsis 121 7 9 2 Member synopsis 121 7 10 Monitor control request 121 7 10 1 Constructor synopsis 122 7 10 2 Member synopsis 122 7 11 SSR control request 122 7 11 1 Constructor synopsis 123 7 11 2 Member synopsis 123 7 12 Down load control request 123 7 12 1 Constructor synopsis 123 7 12 2 Member synopsis 123 7 13 GBM control request 124 7 13 1 Constructor synopsis 124 7 13 2 Member synopsis 124 7 14 Proxy parameters 124 7 14 1 Constructor synopsis 124 7 14 2 Member synopsis 125 7 15 Exceptions 22a 125 7 15 1 Data Stream Allocated 125 7 15 2 No transmit port 125 7 15 3 Network Transmit Failure 125 Appendix A The Datagram support package 127 A 1 Name space VscDatagram 128 A 2 Datagram Assembler 128 Initial public release page 13 The Virtual Spacecraft VSC Table of Contents Users Manual Version Issue 1 4 2 A 2 1 Constructor synopsis A 2 2 Member synopsis A 3 LCI Assembler A 3 3 Constructor synopsis A 3 4 Member synopsis A 4 LPA Assembler A 4 5 Constructor s
109. ns a FALSE value This function throws no exceptions This method returns a reference to the APID range at the head of its range list If the list is empty the reference returned is equal to the reference returned by the last member see below This function throws no exceptions This method returns a reference to the range list By comparing for equality this reference to ranges on the handler s list see the head method the user can determine whether a range is at the tail of the list This function throws no exceptions handle unsigned short This method allocates and constructs an ApidRange see Section 5 6 using a constructor appropriate for creating a range corresponding to the single argument The range is inserted at the tail of the list of the handler s APID range list This method returns no value and throws no exceptions Initial public release page 97 The Virtual Spacecraft VSC Users Manual Chapter5 The Handling package Version Issue 1 4 2 handle unsigned short low unsigned short high This method allocates and constructs an ApidRange see Section 5 6 using a constructor appropriate for creating a range corresponding to the two arguments The created range is inserted at the tail of the handler s APID range list The function returns a reference to the created range This method returns no value and throws no exceptions 5 3 Telemetry Handler This class specifies a handler for a telemetry packets see
110. nspectors Those methods returning the primary header attributes of the packet For example the version member Payload Management Those methods which both manage and control the user payload of the packet For example the payload member Sequencing Those methods which are used to control packet sequencing For example the segFlags function page 78 Initial public release The Virtual Spacecraft VSC Chapter 4 CCSDS package Users Manual Version Issue 1 4 2 The derived classes s interest will most likely be centered around the payload methods as these are the primary mechanism used by an application in order to provide specialization of user s telecommands and telemetry Listing 2 Class definition for Packet 1 2 3 4 5 s 6 7 8 9 10 113 12 13 14 15 16 17 template lt unsigned T gt class Packet protected constructors Packet short apid Packet short apid Ccsds SeqFlags unsigned short seqNum Packet const Packet amp public Packet public Packet amp operator const Packet amp public inspectors unsigned short apid const unsigned short version const unsigned short length const unsigned short seqNum const Cesds SeqFlags seqFlags const bool isTelecommand const 4 3 1 Constructor synopsis Packet short apid This constructor initializes the CCSDS primary header of the packet corresponding to the object as
111. o pick a memory management strategy appropriate to application For example if a packet could be processed and dismissed entirely by the router storage for a single packet is all that is necessary and could be allocated within the router itself If on the other hand arrived packets are meant to be passed through the router to other objects for processing then allocation from a free store would be more appropriate Packet catching Once a packet has arrived and been placed in the memory specified by the router the stream s input port calls back the router s route method in order to dispose of the arrived packet This method searches for a handler see Section 5 2 to catch and process the arrived packet The class specification for the abstract router is found in Listing 17 An application is not expected to directly inherit from this class Instead an application will sub class from one of three type specific routers TelemetryRouter see Section 6 3 ScienceRouter see Section 6 4 TeleCmndRouter see Section 6 5 page 104 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 6 The Routing p ackage Version Issue 1 4 2 Listing 17 Class definition for Router E te 2 3 4 53 6 7 8 9 10 Lal I2 13 14 LS 16 mplate lt class T gt class Router public constructors Router public virtual Router public virtual T allocate 0 virtual void c
112. olated the LAT issues an error when processing a ancillary command By specifying an invalid acquisition time an application can test whether this constraint is correctly enforced For example 1 For clarity the bulk of the construction arguments are omitted Initial public release page 73 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 vsc schedule Attitude 160000 OK TimeTone 239900 OK Attitude 380000 OK Attitude 660000 Error Attitude 762100 A OK Data 801000 OK Attitude 1020000 Error To return to the VSC to its default state of not filling the ancillary slots requires scheduling a null sequence vsc schedule Finally using Figure 22 as an example to schedule a sequence for the second period relative to the initial value of the observatory time base ty define T2 TO unsigned 2 TO is the initial observatory base time vsc schedule T2 Attitude TimeTone Attitude Attitude Attitude Data Attitude 3 8 Administrating the VSC 3 8 1 Configuring queue sizes Each of the six queues described in Section 1 4 1 is assigned by default a maximum number of entries see Table 4 In many cases the default values may prove insufficient In such a case the user may change queue sizes by manip
113. omposite Shell Temperature 34 Thermistor Y ACD Inside Composite Shell Temperature Thermistor Z ACD Inside Composite Shell Temperature 36 Thermistor X_ACD PMT Rail Right Temperature 37 Thermistor Y ACD PMT Rail Right Temperature 38 Thermistor X ACD PMT Rail Right Temperature 39 Thermistor Y ACD PMT Rail Right Temperature 40 Thermistor X LAT Plate Heat Pipe Temperature 1 43 Thermistor X LAT Plate Heat Pipe Temperature 4 44 Thermistor Y Grid Radiator Interface X Side Temperature 45 Thermistor Y Grid Radiator Interface X Side Temperature 46 Thermistor Y Grid Make up Heaters X Side Temperature 49 Thermistor Y Grid Radiator Interface X Side Temperature 50 Thermistor Y Grid Radiator Interface X Side Temperature 51 Thermistor Y Grid Make up Heaters X Side Temperature 52 Thermistor Y Grid Make up Heaters X Side Temperature Figure B 2 Enumeration of 468 board monitored quantities Initial public release page 139 The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring System Version Issue 1 4 2 page 140 Initial public release
114. on passed as an argument to the constructor Note If this request specifies resetting the time base can only be issued if the VSC is currently in a stopped state see Section 1 4 4 Listing 22 Class definition for Scheduler 1 class Scheduler VscCcsds Telcmnd 2 public 3 enum StartPauseStop Start 1 Pause 2 Stop 3 4 public 5 Scheduler Scheduler StartPauseStop unsigned timebase 0 6 public Ta Scheduler 8 public 9 Scheduler StartPauseStop state const 10 public 11 unsigned time const 12 y 7 3 1 Constructor synopsis Scheduler This constructor takes as its first argument an enumeration expressing the state which the scheduler is to be driven See Section 1 4 4 for the meaning of each scheduler state The second argument specifies the new initial value of the time base as measured as the time since the standard epoch 00 00 00 0 hours at January 1 2001 Time is measured in units of seconds A value of zero the default specifies the time base should be set to the current value of the wall clock time base see Section 1 3 1 The constructor throws no exception 7 3 2 Member synopsis state time Returns the requested state expressed as an enumeration The member function has no arguments and throws no exceptions If the request was to reset the time base the function will return the enumeration Stop Returns the initial value of the time base on the
115. on can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 schedule Disables sending the default ancillary sequence See the member function below This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 schedule Attitude amp Transmits a set of seven specific commands on the command stream to the VSC where these telecommands form the default set of ancillary commands The first argument is a reference to the first of the five different default attitude packets see Section 4 10 The second argument is a reference to the default time tone packet see Section 4 12 The third fourth and fifth arguments are references to the next three default attitude packets The sixth argument is a reference to the single default ancillary data packet see Section 4 11 The seventh and last argument is a reference to the fifth and last default attitude packet This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 schedule unsigned time Attitude amp Transmits a set of seven specific commands on the command stream to the VSC where these telecommands are then queued on the VSC for subsequent transmission to the LAT at a time within a specific one second period The period is specified by the first argument whose value represents the number of seconds since
116. ond to the attitude of the Spacecraft with the third argument corresponding to the attitude of the X axis the fourth the Y axis the fifth the Initial public release page 89 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 Z axis and the sixth the so called scaler component The last three arguments correspond to the Spacecraft s angular velocity with the seventh argument corresponding to the velocity of the X axis the eight the Y axis and the ninth the Z axis Ancillary telecommands are transmitted for execution by objects of the class described in Section 7 2 4 10 2 Member synopsis usecs Returns the time within the execution period to schedule the telecommand This time is specified in micro seconds and may range from a value of zero 0 to 999 999 decimal This function has no arguments osJ_1 Returns the X axis component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes constructor This function has no arguments Qsa_2 Returns the Y axis component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000 frame J This value was specified as an argument to the classes constructor This function has no arguments QsJ_3 Returns the Z axis component of the quaternion expressing the attitude of the Spacecraft S with respect to the J2000
117. or The definition for this class page 70 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 class SysReset public TeleCmnd public constructors SysReset unsigned fidO 0 unsigned fidl 0 public destructor SysReset public unsigned fid0 const unsigned fid1 const unsigned fid2 const unsigned fid3 const Although the documentation is not explicit with respect to unused entries in the file ID array the constructors will initialize these entries to null As an example the following code fragment is the implementation of the constructor which requires two IDs SysReset SysReset unsigned fid0 unsigned fidl TeleCmnd APID FUNCTION _MyPayload payload payload fileId 0 fido payload fileId 1 fidl payload fileld 2 0 payload fileld 3 0 copy void payload sizeof _MyPayLoad Last the implementation of one of the four accessor methods unsigned SysReset fid2 unsigned long fileId unsigned long payload return filelId 2 3 7 Scheduling the Magic seven Once a second the VSC sends to the LAT seven 7 ancillary data telecommands These are the so called magic seven commands see Section 4 9 Five of these telecommands are identical in structure and contain attitude information Sectio
118. ority function of the class described in Section 7 14 The functions s argument specifies a pointer to the router to process incoming packets see Section 6 2 The router will be called back once for every received CCSDS telemetry packet One can only register a router once per stream If this member function has been previously called the exception described in Section 7 15 1 will be thrown If this member function cannot transmit the connection request to the VSC due to a network error the exception described in Section 7 15 3 will be thrown This member function returns no value latTelemetry Creates a connection to the VSC s LAT telemetry stream and registers an application specific router to process the telemetry acquired by the LAT and returned through the stream This includes both the so called LAT housekeeping and diagnostic telemetry The router s code is executed in the context of a thread named VscLatTelemetryThread The priority of the thread is specified by adding three 3 to a common base priority The base priority is returned by the basePriority function of the class described in Section 7 14 The functions s argument specifies a reference to the router to process incoming packets see Section 6 2 The router will be called back once for every received CCSDS telemetry packet One can only register a router once per stream If this member function has been previously called the exception described in Section 7 15 1 will be
119. ote interface is called the VSC s Proxy Interface This interface resides on a remote platform both UNIX and Windows based platforms The sum total of the vSc s hardware internal software and external interface constitute a spacecraft simulation Other simulations of the spacecraft exist each with complementary features However the VSC is designed expressly to meet the specific requirements of the LAT and in particular address the needs of the FSW group with respect to the simulation of the science data acquired by the LAT To this end the VSC has some features not required of the spacecraft e interface to the FES Front End Simulator e the ability to set the observatory time to an arbitrary value e the ability to start and stop observatory time e the ability to drive externally the VSC s absolute time and position model e real time access to science data Any application coded against the proxy interface should partition these features in such a way that as the VSC is moved into a more realistic observatory environment these features can either appropriately mutate or be disabled An application coded against the proxy interface would provide its users the fiction of operating the LAT as if it were on orbit Logically if the VSC represents a simulation of the 1 A description of the VSC hardware is found in Chapter 2 2 Hereafter referred to as the Spacecraft S C ICD Interface Control Document Initial public re
120. port for construction of these packets GLAST specifies two different types of CCSDS packets Telecommands and Generic Telemetry see 8 This package provides class representations for both types Tel eCmnd see Section 4 4 and GenericTelemetry see Section 4 6 These representations derive from a common abstract representation of a CCSDS packet The LAT specifies that telemetry comes in two forms Telemetry and Science Applications are expected to construct specific commands and telemetry by sub classing from either of these two classes The package itself sub classes from TeleCmnd in order to form the three different types of telecommands used in the definition of a Magic seven sequence The usage of these specific type of commands is discussed in Section 4 9 The dependencies for the classes of this package are illustrated in Figure 23 Attitude Data M7Cmnd gt TeleCmnd TimeTone y Mangle gt Packet Telemetry Vv SeqFlag LargeTelemetry gt GenricTelemetry Science Figure 23 Class dependencies for the CCSDS package Initial public release page 77 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 4 1 Name space VscCcsds 4 2 Packet sequencing Sequencing is used when any one piece of information transmitted using CCSDS packets cannot fit wit
121. raft VSC Users Manual Chapter 2 Hardware Version Issue 1 4 2 to Serial port to Ethernet port to GPS Antenna 1 2 3 4 5 6 8 8 10 11 12 b i e a OOOO ee O MO O ee JL 235 JL 233 JL 232 JL 234 JL 121 JL 122 JL 124 JL 125 JL 138 JL 145 JLexxx JL xxx EMI shield BPU Figure 17 External Connectivity LAT VSC 2 10 VSC Inter Connectivity Initial public release page 51 The Virtual Spacecraft VSC Users Manual Chapter 2 Hardware Version Issue 1 4 2 page 52 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 Chapter 3 Using the proxy interface Before starting any application assembled from the proxy interface the application user should be satisfied on two counts i There is agreement between the VSC and proxy interface on the VSC s host name and the port numbers used for communication This subject is addressed in Section 3 8 ii The VSC is successfully booted see Section 3 8 Once the VSC is successfully booted the user s application is ready to control the vsc through the proxy interface To do so first the application must establish a connection to the VSC This is v
122. re executed by the VSC in argument order The relative time structure between the execution of these requests and other telecommands transmitted to the LAT is Initial public release page 113 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 discussed in Section 1 4 The arguments are references to a series of objects Each object corresponds to a scheduler request as a telecommand see Section 7 3 to be sent to the LAT This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 execute Controls Transmits a set of up to seven 7 command requests on the command stream to the VSC where these requests are then queued on the VSC for subsequent execution as soon as the VSC has the capability to do so The command requests to execute are represented by the function s arguments Relative to each other these commands are executed by the VSC in argument order The relative time structure between the execution of these requests and other telecommands transmitted to the LAT is discussed in Section 1 4 The arguments are references to a series of objects Each object corresponds to a command request as a telecommand see Section 7 4 to be sent to the LAT This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 execute TeleCmnds Tran
123. rives at the proxy the user handles this information in the same fashion as it would process any other telemetry see Section 3 4 Monitor selection primary or redundant as well as its disabling is available through the proxy interface see Section 7 10 When monitoring is disabled the VSC no longer either acquires or transmits monitoring packets The VSC specifies one APID for the information digitized by the 850 board and one APID for the information digitized by the 468 board Therefore once a second the user can expect to see two different packets on the diagnostic stream The structure and APIDs of these packets are defined in Appendix B Note that the telemetry packet contains a field identifying whether data were acquired with the primary or redundant monitor Different versions of the VSC can contain zero one or both of these boards consequently the actual number of packets transmitted per second is dependent on the number of boards For example if a VSC contains only an 850 board only the packet corresponding to that board is transmitted If the VSC contains neither of these boards nothing will be transmitted In short to acquire and process diagnostic telemetry from the proxy requires atleast one of either an 850 or 468 board the corresponding Systran boards cabling correctly established between LAT and VSC and potentially a BPU router and handler connected to VSC diagnostic stream monitoring to be enabl
124. rs Manual Version Issue 1 4 2 Document Control Sheet Table 1 Document Control Sheet Document Title The Virtual Spacecraft VSC Users Manual Version 1 4 Issue 2 Edition English ID LAT TD 05601 Status Initial public release Created February 9 2002 Date December 5 2005 Access V GLAST Electronics Design DocumentsY VSC V1 4 frontmat ter fm Keywords GASU Based Teststands Tools DTP System Adobe FrameMaker Version 6 0 Layout Software Documentation Version V2 0 5 July 1999 Template Layout Templates Content Version Template Authorship Coordinator Michael Huffer Written by Michael Huffer Table 2 Approval sheet Name Title Signature Date Gunther Haller JJ Russell FLIGHT SOFTWARE LEAD LAT CHIEF ELECTRONICS ENGINEER page 6 Initial public release The Virtual Spacecraft VSC Document Status Sheet Users Manual Version Issue 1 4 2 Document Status Sheet Table 3 Document Status Sheet Title The Virtual Spacecraft VSC Users Manual ID LAT TD 05601 Version Issue Date Reason for change 1 0 1 8 22 2005 First public release 12 1 11 10 2005 Added support for the assembly of science packets to data grams See Section 4 8 and Appendix A 13 1 11 21 2005 Added support for the LAT voltage and temperature monitor ing See Section 3 3 6 Section 7 10 and Appendix B 1 4 1 12 05 2005 After some reflection changed st
125. ructure of monitoring packets Added support for conversion from ADC counts to engineer ing units for these packets See Appendix B Initial public release page 7 The Virtual Spacecraft VSC Users Manual Document Status Sheet Version Issue 1 4 2 page 8 Initial public release The Virtual Spacecraft VSC Users Manual Table of Contents Version Issue 1 4 2 Table of Contents Abstract s 6 80 Sw Ge Pon bk Oe he Oe ER Oe e eh ee a eS Intended audience 2 2 1 O Conventions used in this document 2 2 2 2 we ee ee ee 9 References lt c p 2 6 ww ee a e a A Document Control Sheet 2 2 2 we ee ee 6 Document Status Sheet 2 2 ww eT Listof Tables c s aa a o aok Soe e e aom eee woy ee 1D List of Figures 2 2 4 6 amp amp 8 80m we e we el we at TF Listor Listings o e wos ee ee ee ee a Ee te a da ea da EG te TD Chapter 1 Introduction s so cos e a amp So ee ok Boa a ae ale a we ek 4 Le a 27 1 1 Information Exchange ee ee ee adoa mow 22 1 1 1 Information exchange ere LAT afd vsc ke ee ae we a e a 1 1 2 Information Exchange between VSC and proxy interface 24 1 2 Software methodology and organization 2 1 ee we 25 1 2 1 Documentation conventions 2 1 1 ee ee ee 27 1 2 2 Header files and name spaces 4 4 4 lt 2 ee eee e 4 20 1 2 3 Configuration management 2 i 2 4 te e
126. rvices These classes are grouped together to form a class package The VSC software is comprised of Initial public release page 25 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 ten of these packages Each package corresponds to both an individual name space and individual sets of header files see Section 1 2 2 The relationship between packages is expressed in Figure 3 VscProxy I VscRouting 7 VscCcsds f VscHandlers oan VscNetwork VscDrivers VscQueues gt VscList y VscThread K VscScheduler Figure 3 Class package inter dependencies Each box represents a single package The name of the package is contained within the box Arrows between boxes represent the dependencies between packages with the direction of arrow pointing to the dependent package For example VscRouting and VscDrivers are both dependent on VscDataHanders Dependencies can be of three different forms e inheritance e has a relationship e uses relationship Shaded boxes represent the packages used exclusively for implementation and are expected to have no direct interest to a user or their applications The four unshaded boxes constitute the proxy interface and contain those classes which define the public proxy interface It is from these three packages th
127. ry const GenericTelemetry amp public virtual GenericTelemetry public GenericTelemetry amp operator const GenericTelemetry amp public void copy const void int sizeofPayload void append const void int sizeofBuffer public unsigned short sizeofPayload const unsigned short maxPayload const const unsigned short payload const public unsigned secs const unsigned usecs const 4 6 1 Constructor synopsis GenericTelemetry short apid unsigned secs unsigned usecs SeqFlags short seqNum The CCSDS header is initialized in manner appropriate for a CCSDS telemetry packet see 8 The APID of the packet is derived from the first argument passed to the constructor The allocated payload size is set to zero The second and third arguments specify the time at which the telemetry payload was acquired The second argument corresponds to the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 The third argument corresponds to the acquisition time relative to the second argument This time is measured in micro seconds The forth argument determines the position of the packet in a set of information which spans packets If this argument is omitted the sequence flag is set to alone The fifth argument corresponds to the packet s sequence number If this argument is omitted the sequence number is set to zero The constructor throws no exceptions Initial pub
128. ryRouter public MyRouter MyRouter private Dump _ dump VscCcsds Telemetry packet one packet s worth of storage MyRouter now contains an object of type Dump used for the catchall method see below and also enough storage for any one telemetry sized packet The constructor s implementation simply registers the housekeeping handler defined in Section 3 4 MyRouter MyRouter _dump Unexpected packet insert new Houskekeeping When a packet arrives it will be copied into this storage by the proxy interface The interface locates where to copy the packet by invoking the router s allocate method As this method is virtual MyRouter provides the implementation which is simply VscCcsds Telemetry amp MyRouter allocate return _packet If the handler cannot catch all packets they will be caught and processed by the router s catchall method This method is virtual so MyRouter must provides the implementation Initial public release page 67 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 void MyRouter catchall Telemetry amp packet _ dump decode packet return Note that the catchal1 handler has the same call interface as a handler s process member Indeed in this example the implementation almost matches MyHandlers s process implementat
129. s and throws no exceptions maxPayload Returns the actual amount of storage reserved for a payload The current allocation of the payload is returned by the function described above This function has no arguments and throws no exceptions secs Returns the time at which the telemetry payload was acquired This time is returned as the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 This function has no arguments and throws no exceptions usecs Returns the time in micro seconds relative to the time returned by the secs member function described above This function has no arguments and throws no exceptions 4 7 Telemetry Telemetry packets are simply sub classed from GenericTelemetry see Section 4 6 with the template packet size argument satisfied Telemetry packets are fixed size independent of the actual allocated payload size 1024 bytes That is the maxPayload function will return 1024 bytes less the size of the header Telemetry packets are delivered on both the LAT and vsc telemetry streams see Section 7 2 page 86 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 Listing 6 Class definition for Telemetry 1 class Telemetry public GenericTelemetry lt 1024 gt 2 public constructors 3 Telemetry short apid 4 unsigned secs unsigned usecs 5 SeqFlags flags alone unsigned short seqNum 0 6 Telemetry const Telemetrys amp
130. seconds and micro seconds The seconds quantity represents the acquisition time as the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 The micro seconds quantity is the acquisition time in micro seconds relative to the seconds quantity LAT telemetry comes in two varieties largely differentiated by their maximum size i ii Telemetry All small telemetry is fixed size independent of actual allocated payload size 1024 bytes That is the maxPayload function will return 1024 bytes less the size of the header Telemetry packets are delivered on the LAT and VSC telemetry streams see Section 7 2 Science All science telemetry is fixed size independent of actual allocated payload size 4096 bytes That is the maxPayload function will return 4096 bytes less the size of the header Science packets are delivered on the LAT s science stream see Section 7 2 A discussion on how telemetry is processed by a user application is found in Section 3 4 page 84 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 Listing 5 Class definition for GenericTelemetry il 2 3 4 58 6 T 8 93 10 iis T2 13 14 153 16 I7 18 19 20 ls class GenericTelemetry public Packet lt T gt protected constructors GenericTelemetry short apid unsigned secs unsigned usecs SeqFlags unsigned short seqNum GenericTelemet
131. smits a set of up to five 5 commands on the command stream to the VSC where these telecommands are then queued on the VSC for subsequent transmission to the LAT as soon as the VSC has the capability to do so The commands necessary to transmit are represented by the function s arguments Relative to each other these commands are transmitted to the LAT in argument order The relative time structure between these and other telecommands transmitted to the LAT is discussed in Section 1 4 The arguments are references to a series of objects Each object corresponds to a telecommand see Section 4 4 to be sent to the LAT This function returns no value This function can throw either one of the exceptions described in Section 7 15 2 and Section 7 15 3 executeAt unsigned time Controls Transmits a set of up to seven 7 command requests on the command stream to the VSC where these requests are then queued on the vsc for subsequent execution at a time within a specific one second period The period is specified by the first argument whose value represents the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 The command requests to execute are represented by the arguments following the period first argument Relative to each other these requests are transmitted to the LAT in argument order The relative time structure between the execution of these requests and other telecommands transmitted to the LAT is discussed
132. specific router to process the telemetry acquired by the vsc and returned through the stream The set of potential telemetry returned by the VSC is described in xxx The router s code is executed in the context of the thread named VscTelemetryThread The priority of the thread is specified by adding two 2 to a common base priority The base priority is returned by the basePriority function of the class described in Section 7 14 The functions s argument specifies a reference to the router to process incoming packets see Section 6 2 One can only register a router once per stream If this member function has been previously called the exception described in Section 7 15 1 will be thrown If this member function cannot transmit the connection request to the vsc due to a network error the exception described in Section 7 15 3 will be thrown This member function returns no value page 112 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 latDiagnostic Creates a connection to the VSC s LAT diagnostic stream and registers an application specific router to process the diagnostic telemetry acquired by the LAT and returned through the stream The router s code is executed in the context of the thread named VscLatDiagnosticThread The priority of the thread is specified by adding one 1 to a common base priority The base priority is returned by the basePri
133. st VscCcsds const const const const VscCcsds const VscCcsds VscCcsds VscCcsds VscCcsds VscCcsds vscTelemetry VscRouting TelemetryRouter amp latDiagnostic VscRouting TelemetryRouters amp latTelemetry VscRouting TelemetryRouter amp adr ttitudes amp imeTone amp ttitude amp ttitudes amp ttitudes amp ata amp ttitude amp gt UD e Initial public release page 111 The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 7 2 1 Constructor synopsis Proxy This constructor creates an output port which is then connected to the VSC s command stream In order to successfully connect this stream requires the VSC s node name and command port number These parameters are specified by an instance of the class described in Section 7 14 The constructor has no arguments The constructor throws the exceptions Section 7 15 2 and Section 7 15 3 Proxy Parameters This constructor creates two output ports which are then connected to the VSC s control stream and command streams In order to successfully connect these two streams requires the VSC s node name control and command port numbers These parameters are specified by an instance of class described in Section 7 14 The application can over ride one or more these parameters by providing its own instance of the proxy s parameters The argument is a
134. t they are intended to route The user is expected to sub class from one of these three routers in order to construct their own specific router All routers and their corresponding handlers see chapter 5 execute in the context of a specific thread see Section 1 1 The dependencies of the classes of this package are described in Figure 25 o ScienceRouter aac gt ScienceHandler Router TeleCmndRouter gt TeleCmndHandler Vv Packet TelemetryRouter gt TelemetryHandler Figure 25 Class dependencies for the Routing package Initial public release page 103 The Virtual Spacecraft VSC Users Manual Chapter 6 The Routing package Version Issue 1 4 2 6 1 Name space VscRouting 6 2 Router This class which forms an base class for the specific routers described below is used to route incoming CCSDS packets carried on a stream see for example the Proxy class described in Section 7 2 A stream delegates two responsibilities to a router in order to handle packets on their arrival These are i ii Packet memory allocation The stream s input port calls back an application derived function allocate in order to place the arrived packet into a user specified area In this fashion the stream relinquishes memory allocation responsibility and passes that responsibility to the router This allows the router t
135. ta Returns the size in bytes of the datagram portion of the corresponding CCSDS packet This function has no arguments and throws no exceptions 4 9 The Magic 7 Telecommands To be written Listing 8 Class definition for M7Cmnd 1 class M7Cmnd public TeleCmnd 2 public 3 enum FunctionCode Attitute 1 Data 2 TimeTone 3 4 public constructors 5 M7Cmnd FunctionCode 6 M7Cmnd const M7Cmnd amp 7 public 8 M7Command 9 public 10 M7Cmnd amp operator const M7Cmnd amp 11 public 12 unsigned period const 13 unsigned isPeriod unsigned time 14 y 4 9 1 Constructor synopsis M7Cmnd This constructor builds a generic ancillary GLAST telecommand as specified in 8 This class forms the base class for the specific ancillary telecommands described in sections 4 10 4 10 and 4 10 and thus has little or no intrinsic interest in and of itself The argument corresponds to one of the three possible functions codes corresponding to the three different types of ancillary telecommands The execution period time field associated with the ancillary telecommand is initialized to zero 0 Ancillary telecommands are transmitted for execution by objects of the class described in Section 7 2 4 9 2 Member synopsis period This function returns the current period value This function throws no exceptions page 88 Initial public release Users Manual Version Issue 1 4 2 T
136. te Stop put the VSC into a stopped state Set Time Request a modification of the VSC s time base see Section 1 3 The telecommand parameter specifies the new value of the time base Like all telecommands sent on the command stream the user queues these telecommands through the proxy interface In this particular case the interface is contained within the Proxy class discussed in Section 7 2 Figure 8 illustrates the combination of states and permitted transitions set time O time start pause Flushing queues start pause Stopped set time initialize Setting time Figure 8 vsc Finite State Machine Diagram To summarize the main features of this diagram The scheduler comes up in a Stopped state Two of these states Flushing queues and Setting time are transitory states One can only modify the time base in the Stopped state The principle difference between the Paused and Stopped states is that a transition to the stopped state will flush the queues page 38 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 Initial public release page 39 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 page 40 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 2 Hardware Version Issue 1 4 2 Chapter 2 Hardware Physically the VSC consists of up to eight different types of modules Seve
137. tem Version Issue 1 4 2 B 3 Telemetry from the 468 board The spread sheet illustrated in Figure B 2 enumerates the quantities monitored by the 468 board and encapsulated in the telemetry packet whose APID is defined in Section B 3 8 Each entry in the spread sheet corresponds to one specific monitored quantity For each quantity the spread sheet specifies the relative location of its data sensor type and description Data offsets are described in units of 16 bit decimal words with offset zero 0 beginning immediately following the standard telemetry header i e the start of the packet s payload For example offset twenty six 26 corresponds to a measurement of the X tile temperature The sensor type is Rtd and specifies temperature as measured through a RTD page 138 Initial public release The Virtual Spacecraft VSC Users Manual Appendix B_ Telemetry from the Monitoring System Version Issue 1 4 2 B 3 8 APID 0x00A4 Conversion Description Thermistor Y VCHP XLHP Interface X Side Temperature 12 Thermistor Y Spare Temperature channel 0 Rtd Y Radiator Panel Upper Left Survival Heater Temperature 14 Y VCHP Reservoir Heater Temperature 3 Y VCHP Reservoir Heater Temperature 4 Y VCHP Reservoir Heater Temperature 5 _25 Thermistor Y Spare Temperature channel 0 26 32 Thermistor X ACD Inside Composite Shell Temperature 33 Thermistor Y ACD Inside C
138. ter s route method see above whenever either its handler list is empty or it cannot find a handler on its list willing to catch the CCSDS packet associated with the call to the catch method The argument to the method specifies a reference to the corresponding packet This function returns no value and throws no exception Initial public release page 105 The Virtual Spacecraft VSC Users Manual Chapter 6 The Routing package Version Issue 1 4 2 head last insert This method returns a pointer to the handler at the head of the router s handler list If the list is empty the pointer returned is equal to the reference returned by the last member see below This function throws no exception This method returns a reference to the router s handler list By comparing for equality this return value to the handlers on the list see the head method the user can determine whether the handler is the range at the tail of the list This function throws no exception This method inserts the handler specified by its argument at the tail of the handler s own list The argument is a reference to the handler see Section 5 2 to insert on the list The method returns a reference to the inserted handler This function throws no exceptions 6 3 Telemetry Router This class specifies a router for a telemetry packets arriving on a telemetry stream see Section 7 2 The implementation of this class simply derives from Router se
139. the Proxy class passing as arguments the seven ancillary telecommands see Section 7 2 to be used as the default set Fill with a different set of commands for each period The application defines a set of commands queues these commands to the VSC where they are stored waiting execution on the appropriate period Once a sequence for a particular period is defined the application calls the schedule member of the Proxy class see Section 7 2 to queue the sequence for that period The arguments to this function specific the seven commands of the sequence along with the particular time period the corresponding commands should be scheduled A period is specified in GLAST standard units the number of seconds since the epoch 00 00 00 0 hours at January 1 2001 1 vsc schedule Attitude 170000 210000 Attitude 370000 Attitude 570000 Attitude 770000 Data 810000 Attitude 970000 TimeTone The first argument of any magic seven command specifies the acquisition time of the data associated with that instance of the command The acquisition time is specified in microseconds relative to the time period For example the code snippet above specifies that the data for the timetone command always occurs 2100 microseconds into any one period Note that the LAT constrains the acquisition time for a command to fall within the slot corresponding to that command If this constraint is vi
140. the line is to be changed If the bit at the offset is clear the line s value is left unchanged The new values of the discrete lines are determined by the values member function described below This function has no arguments and throws no exceptions Returns the values of the discrete lines changed The discrete lines changed are determined by the lines function described above Each bit offset corresponds to a line If the bit at a specified offset is set and the corresponding bit offset in the returned value from the lines function is set the line is to be enabled If the bit at a specified offset is clear and the corresponding bit offset in the returned value from the lines function is set the line is to be disabled This function has no arguments and throws no exceptions page 120 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 79 SIU reset control request The function of this request is to issue a reset to the currently selected SIU on its currently selected path See Section 3 3 1 for a discussion on how the SIU and its path are selected Listing 27 Class definition for Reset 1 class Reset public Control 2 public 38 Reset 4 public 5 Reset 6 y 7 9 1 Constructor synopsis default 7 9 2 Member synopsis none 7 10 Monitor control request The function of this request is to either enable or disable th
141. the work lists associated with the LAT requests immediate and stored control queues see Table 4 Control telecommands provide direction to the VSC For example a request to download diagnostic telemetry see xxx for a list of these telecommands In order to bound the time used by this phase the maximum number of control telecommands which can be executed during any one period is arbitrarily limited to eight 8 however the sum of the telecommands on the three lists could be as many as sixteen 16 The schedular priorities telecommand execution by processing the commands on the stored work list first followed by the commands on the immediate work list and last by the commands on the LAT work list The number of immediate commands executed is the minimum of the difference between the maximum 8 1 Rounded to a period boundary Initial public release page 35 The Virtual Spacecraft VSC Users Manual Chapter 1 Introduction Version Issue 1 4 2 and the number of stored commands processed and the number of commands on the immediate work list any commands on the immediate which cannot be processed will be deferred to the subsequent period Note that at most seven 7 telecommands can be on a stored work list This ensures that independent of the number of stored telecommands at least one immediate telecommand is executed per period This phase occurs within slot zero 0 1 4 3 4 Scheduling command work During this phase
142. ther stream The direction of the arrow represents the direction information flows on the stream Note that for some streams information flow is bi directional 1 1 1 Information exchange between LAT and VSC 1553 All information transferred by the 1553 stream is encapsulated as CCSDS packets and these packets can flow in either direction between VSC and LAT The LAT and VSC specify the type of these packets as either telecommands or telemetry see chapter 4 Telecommands received by a recipient direct that recipient to perform some generic type of action Telemetry received by a recipient contains generic information about the state or health of the entity sending the packet The LAT breaks its telemetry arbitrarily into two types diagnostic and housekeeping see 18 An example of a telecommand would be a dump memory request sent by the VSC to the LAT specifying an upload of a specific piece of memory on the processor within a SIU An example of telemetry would be a packet sent by the LAT to the VSC describing the current bias voltage of an ACD FREE board Initial public release page 23 The Virtual Spacecraft VSC Chapter 1 Introduction Users Manual Version Issue 1 4 2 reset discretes science 1 PPS monitoring Telecommands can either be directed to the LAT by the VSC or directed to the VSC by the LAT Telemetry may be received only by the vsc from the LAT The set of possible telecommand and telemetry packe
143. tic telemetry sourced by the LAT but which are brought out to the proxy interface through the vsc That stream is the LAT telemetry stream described below LAT telemetry This stream transmits CCSDS telemetry from the VSC to the proxy interface This telemetry is the LAT housekeeping and diagnostic telemetry which was brought into the VSC through the 1553 interface between VSC and LAT The set of CCSDS packets which constitute the allowed telemetry on this stream are enumerated and described within the The GLAST Command and Telemetry Database see 18 Note that this stream is independent of the VSC telemetry stream That stream is the VSC telemetry stream described above Science This stream transmits CCSDS telemetry from the VSC to the proxy interface This telemetry is the LAT science telemetry which was brought into the VSC through the science interface between VSC and LAT The science stream carries both the LAT s events and science telemetry The set of CCSDS packets which constitute the allowed telemetry on this stream are enumerated and described within the The GLAST Command and Telemetry Database see 18 1 2 Software methodology and organization Software used for both the vsc and its proxy interface is based on object oriented model with C as the implementation language Consequently the interface is expressed primarily as a series of classes Many of the classes work together to provide a single coherent set of se
144. tion Version Issue 1 4 2 pending list At an appropriate time the scheduler as described in Section 1 4 3 removes a work request from the head of the pending list performs the corresponding work and then returns the work request by inserting at the tail of the free list There are seven different activities which compete for the scheduler s resources and thus the VSC assigns to each activity its own queue Each queue is differentiated by three parameters i The maximum number of telecommands held by any one work request ii Sort order Entries may be ordered either in arrival time or execution time A queue which sorts by arrival time is called an immediate queue A queue which sorts by execution time is called a stored queue iii The maximum number of pending work requests Each queue has default value but this value can be user configured see Section 3 8 1 The parameterization of these seven queues is enumerated within Table 4 Table 4 Queue scheduling order name type Contains maximum size Transistion Immediate VSC scheduler state transitions i 16 ControlStored Stored VSC control telecommands 7 16 Control Immediate VSC control telecommands 7 16 Ancilliary Stored LAT ancillary telecommands 7 8192 CommandStored Stored LAT telecommands 8 16 Command Immediate LAT telecommands 5 16 1 Expressed as the maximum number of telecommands per work request 2 This is th
145. tion of 468 board monitored quantities page 18 Initial public release The Virtual Spacecraft VSC Users Manual List of Listings Version Issue 1 4 2 List of Listings Listing 1 p 78 Enumeration for packet sequence flags Listing 2 p 79 Class definition for Packet Listing 3 p 81 Class definition for TeleCmnd Listing 4 p 83 Class definition for Mangle Listing 5 p 85 Class definition for GenericTelemetry Listing 6 p 87 Class definition for Telemetry Listing 7 p 87 Class definition for Science Listing 8 p 88 Class definition for M7Cmnd Listing 9 p 89 Class definition for Attitude Listing 10 p 91 Class definition for Data Listing 11 p 93 Class definition for TimeTone Listing 12 p 96 Class definition for Handler Listing 13 p 98 Class definition for TelemetryHandler Listing 14 p 98 Class definition for ScienceHandler Listing 15 p 99 Class definition for TeleCmndHandler Listing 16 p 100 Class definition for ApidRange Listing 17 p 105 Class definition for Router Listing 18 p 106 Class definition for TelemetryRouter Listing 19 p 107 Class definition for ScienceRouter Listing 20 p 107 Class definition for TeleCmndRouter Listing 21 p 111 Class definition for Proxy Listing 22 p 116 Class definition for Scheduler Listing 23 p 117 Class definition for Control Listing 24 p 118 Class definition for SiuInterface Initial public release page 19 The Virtual Spacecraft VSC List of Listings Users Manual Version Issue 1
146. tocol is packet oriented and layered on standard TCP IP connections The act of instantiating the Proxy class creates all appropriate network connections to the VSC Because of their pervasive usage throughout the observatory the on wire packet protocol is based on CCSDS see 17 and 18 packets The proxy can be thought of as the nexus of six different network streams Five of these streams transmit down linked packets from the VSC to the proxy and one transmits up linked information from the proxy to the vsC Up linked information consists of CCSDS telecommands These telecommands fit into two generic classes Requests Directions to the VSC itself Each individual request has a corresponding class however all vsc requests inherit from the same base class Request TeleCmnds Directions to the LAT which are sent through the vsc The base class for LAT specific telecommands is defined in Section 4 4 VSC requests and LAT telecommands are transmitted by the application to the vsc by calling the schedule and scheduleAt member functions The arguments to these functions consist of either requests or LAT telecommands to be sent to the VSC Both functions allow an application to package up and transmit sets of packets Once arrived on the VSC these packets may be either queued for immediate action or transmission by the VSC implicitly identified page 110 Initial public release The Virtual Spacecraft VSC Chapter 7 The VSC proxy p
147. try packet to be emitted on the VSC diagnostic stream The set of allowed APIDs is specified by xxx This constructor throws no exceptions 7 12 2 Member synopsis apid Returns the APID of the telemetry packet to be down loaded The function has arguments and throws no exceptions tid Returns the transaction ID for the request The transaction ID is a unique number generated by the constructor and reflected back in the emitted telemetry The function has arguments and throws no exceptions Initial public release page 123 The Virtual Spacecraft VSC Chapter 7 The VSC proxy package Users Manual Version Issue 1 4 2 7 13 GBM control request The function of this request is to transmit a GRB pulse to the LAT Listing 31 Class definition forterb 1 class Grb public Control 2 public 3 Grb 4 public 5 Grb 6 y 7 13 1 Constructor synopsis default 7 13 2 Member synopsis none 7 14 Proxy parameters To be written Listing 32 Class definition for Parameters 1 class Parameters 2 public constructors 3 Parameters 4 public 5 Parameters j 6 public 7 virtual const char vsc 8 public 9 virtual int control 10 public 11 virtual int basePriority 12 y 7 14 1 Constructor synopsis Parameters To be written page 124 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy packa
148. ts exchanged between LAT and VSC is defined by the observatory Command and Telemetry Database see 18 Is a specific type of discrete request sent by the VSC to the LAT This request issues a reset to the currently selected SIU This request causes not only a re boot of the SIU s processor but also causes the SIU to issue a global reset to the entire LAT Discretes are simply digital boolean signals exchanged between LAT and VSC The VSC can assert deassert three 3 different discrete signals to the currently selected SIU The currently selected SIU can assert deassert four 4 different signals to the VSC These signals are typically used as boot flags between VSC and LAT see 8 Information sent on this stream contains the LAT s science data This data includes both the LAT s accepted events and housekeeping science telemetry Independent of type of data information sent on this stream is encapsulated as CCSDS packets This is a signal pulse sent by the VSC to the LAT once a second This signal is sent with great precision by the VSC to allow accurate correlation of time between VSC and LAT The absolute time corresponding to any one particular pulse is sent sometime later by the VSC to the LAT as a 1553 telecommand the time tone message see Section 4 12 Normally this pulse and its corresponding absolute time is maintained with great precision by the VSC using a GPS receiver See Section 1 3 for a discussion of how time
149. uInterface 6 public 7 VscProxy Path path const 8 y 7 6 1 Constructor synopsis SiuInterface This constructor takes as an argument the enumeration described in Section 7 5 This enumeration determines the exact cross strapping option requested If the argument is omitted the cross strapping request is equal to the initial cross strapping established by the vsc The constructor throws no exceptions 7 6 2 Member synopsis path Returns the enumeration described in Section 7 5 This enumeration specifies which one of the four cross strapping options is implied by the request This function has no arguments and throws no exceptions 7 7 DAQ interface control request The LAT has one GASU which contains two DAQ boards One DAQ board is designated as the Primary DAQ board and the other as the Redundant DAQ board Only one of the two DAQ boards is active at any one time In turn the spacecraft mitigates against single point failure by having two DAQ board interfaces One interface is called out as the Primary LAT interface page 118 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 7 The VSC proxy package Version Issue 1 4 2 and the other as the Redundant LAT interface which the VSC emulates In order to support full redundancy each of the four units has both an A and B port The DAQ boards and vsc interfaces are physically cross strapped in order to allow mixing and matching of t
150. ulating an argument to the init _vsc procedure This procedure is called within the VSC s startup script This script is managed as part of any VSC release and consequently is under the control of the FSW code management and release system see xxx The path specification for this script is as follows VSC lt tag gt ptd startup mv2304 vsc vx where the lt tag gt token is replaced with a number corresponding to whatever release is appropriate to the user The argument used to modify the default values is a string which page 74 Initial public release The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 consists of a comma separated list each item of the list corresponding to the value for a particular queue The syntax of this string is as follows n lt name gt lt count gt lt name lt count gt Tokens expressed in brackets for example lt name gt are replaced by the user There are two replaceable tokens name Is a string corresponding to the name of the queue Allowed queue names are enumerated in Table 4 Correct capitalization is necessary count Is an unsigned non zero number corresponding to the size in entries of the queue The number s radix can be expressed in either decimal or hexadecimal A hexidecimal value is specified by the digit 0 followed by one of the letters x or X followed by a string of hexadeci
151. unsigned short sizeofPayload const 18 unsigned short recordedChecksum const 19 unsigned short computedChecksum const 20 4 4 1 Constructor synopsis TeleCmnd short apid short function The CCSDS header is initialized in manner appropriate for a CCSDS telecommand packet see 16 and 17 The APID of the packet is derived from the first argument passed to the constructor and the packet s function code is derived from its second argument The payload size is set to zero The constructor throws no exceptions TeleCmnd const Mangle amp short apid short function The CCSDS header is initialized in manner inappropriate for a CCSDS telecommand packet This constructor should be used only when one is testing the LAT s response to an ill formed telecommand The first argument is a reference to an object see Section 4 5 which defines which fields of the constructed packet should be malformed The APID of the packet is derived from the second argument passed to the constructor and the packet s function code is derived from its third argument The payload size is set to zero The constructor throws no exceptions Initial public release page 81 The Virtual Spacecraft VSC Users Manual Chapter 4 CCSDS package Version Issue 1 4 2 4 4 2 Member synopsis copy Copies the data specified by the argument into the payload of the packet Any data currently in the payload is lost The first argument is a pointer to a buf
152. urn The implementation of this method simply calls its own decode function To actually catch and process arriving telemetry this handler must be both instantiated and registered with a router as discussed in Section 3 5 3 4 1 APID filtering In many cases a handler s goal is to catch a specific type of telemetry Typically the type of a CCSDS packet is determined by its APID Therefore catching a specific type of telemetry amounts to catching a specific set of APIDs This requires a straightforward usage of the methods of the Handler and ApidRange classes The ApidRange class allows the user to define a range of APIDs The constructor for this class requires two short numbers One number corresponds to the lowest APID of the range and the other the highest APID of the range If the range corresponds to a single APID the low and high values are equal The Handler maintains a list of ApidRanges This list defines the set of APIDs which the handler is prepared to catch As an example assume a handler is necessary to catch and processes only LAT housekeeping As defined by the ICD see 18 all housekeeping APIDs fit with a range which varies from 200 to 25F hexadecimal The handler needed for housekeeping simply inherits from the previously defined MyHandler Initial public release page 65 The Virtual Spacecraft VSC Users Manual Chapter 3 Using the proxy interface Version Issue 1 4 2 Houeskeeping public
153. value is expected Their sequence number is monotonically increasing Their contributed size will not cause the datagram to overflow If any of these constraints are violated the datagram cannot be successfully assembled The class discards the runt pending datagram and triggers the unexpected method This method receives as an argument the unexpected packet the expected state and sequence flags Typically this class is not used directly Instead use one of the two derived classes LciAssembler see Section A 3 or LpaAssembler see Section A 4 The definition for this class is contained in Listing A 1 Listing A 1 Class definition for Assembler 1 class Assembler public VscHandling ScienceHandler 2 public 3 Assembler unsigned maxDatagramSize 4 public 5 virtual Assembler 6 public 7 virtual void validate const VscCcsds Sciences 0 8 virtual void dispose const Datagram amp unsigned fragments 0 9 virtual void unexpected const VscCcsds Science amp 10 unsigned state unsigned seqNum 0 11 public 12 unsigned maxDatagramSize const 13 1 The explanation for state is TBD page 128 Initial public release The Virtual Spacecraft VSC Users Manual Appendix A The Datagram support package Version Issue 1 4 2 A 2 1 Constructor synopsis Assembler The argument is the maximum size in bytes of any datagram expected to be assembled by the class
154. y Figure 2 p 23 Logical relationship of the VSC and its external interface to the observatory Figure 3 p 26 Class package inter dependencies Figure 4 p 31 Command and Control flow through the vsc Figure 5 p 32 vsc queue both immediate and stored Figure 6 p 34 Scheduling within a period Figure 7 p 34 Phases within a period Figure 8 p 38 vsc Finite State Machine Diagram Figure 9 p 42 SBC and 1553 interface Figure 10 p 43 GPS receiver Figure 11 p 44 Science interface Figure 12 p 45 Vsc components Figure 13 p 46 Digitizer Figure 14 p 47 VSC 850 module Figure 15 p 49 Corner teststand configuration Figure 16 p 50 Internal Connectivity LAT VSC Figure 17 p 51 External Connectivity LAT VSC Figure 18 p 56 One proxy interface processing all telemetry streams Figure 19 p 56 Multiple proxy interfaces Figure 20 p 58 SIU cross strapping Figure 21 p 61 DAQ board cross strapping Figure 22 p 72 Scheduling the Magic seven Figure 23 p 77 Class dependencies for the CCSDS package Initial public release page 17 The Virtual Spacecraft VSC List of Figures Users Manual Version Issue 1 4 2 Figure 24 p 95 Class dependencies for the Handler package Figure 25 p 103 Class dependencies for the Routing package Figure 26 p 110 Class dependencies for the proxy package Figure A 1 p 127 Class dependencies for the datagram support package Figure B 1 p 137 Enumeration of 850 board monitored quantities Figure B 2 p 139 Enumera
155. ynopsis A 4 6 Member synopsis A 5 Exceptions Appendix B Telemetry from the Monitoring System B 1 Unit conversion a B 1 1 LAT voltage LatV B 1 2 BPU voltage BpuV B 1 3 BPU Current Bpul B 1 4 DAQ Current Daq l B 1 5 Thermistor B 1 6 RTD en B 2 Telemetry from the 850 board B 2 7 APID 0x00A8 B 3 Telemetry from the 468 board B 3 8 APID 0x00A4 129 129 130 130 130 130 131 131 131 133 133 134 134 134 134 135 135 135 137 138 139 page 14 Initial public release The Virtual Spacecraft VSC List of Tables Users Manual Version Issue 1 4 2 List of Tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 p 6 p 6 p 7 p 33 p 59 p 61 p 68 p 78 p 117 Document Control Sheet Approval sheet Document Status Sheet Queue scheduling order Cross strapping options for the siu interface Cross strapping options for the DAQ interface Streams and registration methods Enumeration of sequence flag for a CCSDS telemetry packet Cross strapping options Initial public release page 15 The Virtual Spacecraft VSC Users Manual List of Tables Version Issue 1 4 2 page 16 Initial public release The Virtual Spacecraft VSC Users Manual List of Figures Version Issue 1 4 2 List of Figures Figure 1 p 22 Logical relationship of the VSC and its proxy interface to the observator

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