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The SQIID User`s Manual

1. The DSP unit a VME based Digital Signal Processor system located inside the black Heurikon box in the computer room contains eight transputers that provide the math processing needed to do coadding as the data are taken and buffer space for finished data before it is transferred to the SUN computer e The B016 unit a programmable dual port memory and interface board located inside the black Heurikon box in the computer room interfaces the transputers and the SUN and handles the formatting of data before it is saved to disk Communications between SQUD and the DSP take place over transputer links implemented on an optical fiber cable The BO16 interconnects the transputer DSP to the SUN SparcStation computer via a VME to SBUS converter within the Heurikon box The WILDFIRE user interface on the SUN is implemented within the TCL tool command language environment On startup one can configure the image save to produce either FITS images or IRAF images via IMFORT routines so that they can be manipulated and archived to tape within IRAF The image data are generated in IEEE 32 bit floating point format It is important to note that these images are NOT PROTECTED in any way and can be overwritten if the full path names of existing and new images are the same Currently the saver task attempts to manage conflicting filenames by appending nnn to the incoming conflicting filename The data may be written to Exabyte or DAT tapes on local tape dri
2. Login Password Login as telescope where telescope is 2meter or 4meter as appropriate with the current password posted on the workstation terminal The WILDFIRE system will then load automatically resulting in a terminal screen layout approximately like Fig 5 below the dashed window labeled Instrument Status will appear in the approximate position shown only after the instrument microcode has been loaded Normal WILDFIRE Startup The Windows Once the environment has been set to WILDFIRE by obsinit it will remain in that state even if it is necessary to reboot the instrument computer for any reason There should be no reason to execute obsinit more than once during a run If a reboot is required the login procedure in the window displayed above will automatically bring up the WILDFIRE windows USTRUBENT COMNTACL DATA RED UVCTEN Fig 5 Windows layout after initiation of WILDFIRE A brief description of the windows follows e 1 Instrument Control This is the window for entering all commands controlling the instrument or telescope It will initially have a instrument computer prompt and a prompt when the instrument microcode is running e 2 IRAF XGTERM This window is used for IRAF commands for analysis of data or for shell commands such as creating directories moving or archiving data e 3 Instrument Status Once the instrument microcode has been loaded this window will appear Instru
3. by a factor of two with edge vignetting because it is too small to service the full FOV Although one can obtain useful data at JHKL within the central field with the polarizer in place the vignetting near the edge which is variable since we do not put a close tolerance on the indication when the polarizer is in position is problematic It is also worth remembering that for polarized sources your signal loss will be larger Table 7 Estimated SQIID performance variation ambient temperature A Mbini J H K L comments Temperature 0 21 0 35 magnitudes improvement DE 1000 POOU ay Nosy backeround relative to SOP 0 00 0 00 magnitudes improvement OU PONORA eo VO ltbackeround telative 16508 70 F 40 00 0 00 0 30 0 31 magnitudes improvement 1 7 1 8 background relative to 50F Table 8 Estimated SQIID performance variation Precipitable Water Vapor PWV J H K L comments 0 02 0 19 magnitudes improvement em eee ee 1 02 1 12 background relative to 6mm 0 00 0 00 magnitudes improvement Grimi ON 1 00 1 00 background relative to 6mm 0 03 0 26 magnitudes improvement 0 98 0 84 background relative to 6mm 0 06 0 54 magnitudes improvement 0 95 0 67 background relative to 6mm 3mm 0 00 0 00 Imm 0 00 0 00 System Overheads To optimize observing efficiency it is important to keep the two distinctly different system overheads in mind related to e Data pipeline flow 40 se
4. process a likely culprit is a bad or incorrect if the failure occurs on the initial setup fiber optic connection Check the three status LEDs visible through sight holes on the SQIID electronics The left LED should be green if there is power to the instrument the middle and right LEDs should be off If either the middle channel 1 or right channel 2 LED is red there is a fiber continuity problem in that channel There is a duplicate set of LEDs in the Heurikon DSP box in the computer room reporting on the other two fibers it is necessary to remove the front cover to view them A bad fiber channel will require the substitution of one of the spare fibers Call for assistance WILDFIRE RESTART PROCEDURES The following procedures are intended as a guide for restoring the WILDFIRE system following various levels of system failure Re booting the computer and cycling power to the instrument or DSP in the Heurikon box in the computer room are not normal WILDFIRE operations and should not be done without proper consultation or unless the specific conditions below are valid These procedures are listed roughly in order of increasing severity so unless a specific condition has occurred e g DSP power cycling try the less dramatic procedures first An extensive troubleshooting library may be consulted by entering trouble in any active window except the Instrument Control window The resulting interactive session can be used to diagnose and
5. To execute the script enter the base name scriptname as a command in the Instrument Control window A sample script is given in Appendix IV Scripts may be found in directory tclSamples under the telescope directory as in the path above and also in usr wfire tcl This latter path is the system response to query pwd in the Instrument Control window When creating a custom script please copy a system script into an observer directory and then rename and modify it to avoid confusion Scripts copied into the user home script directory data2 2meter wfire at the 2 1 m and data2 4meter wfire at the 4 m and sourced can be marked for automatic inclusion in subsequent invocations of startwf by entering mkIndx For the more sophisticated or daring observer a TCL manual is available WILDFIRE presently uses TCL version 6 7 and properly written code should run with no special limitations Please note we will not debug or otherwise support user code nor will user supplied TCL routines be saved within WILDFIRE from one observing run to the next The following WILDFIRE default scripts are useful for various observing programs and as templates for user constructed modification They are initiated by entering the script name as a command and going through a series of interactive queries to set internal parameters Alternatively several have command line versions for faster use These are default scripts which do not require sourcing e
6. You will be prompted to put the name of the image you want sky subtracted and the identity of the sky image The sky image can either be the name of another image the special entry prev which indicates the previous image or an ordinal number offset or from the image in the first entry e Image statisitics for the two frames and their difference will be also be displayed e Ifyou set dolast yes either using the IRAF epar or appending dolast to the command line idisp will display the sky subtracted result from the most recent image using the filename and channel parts of the first entry e Ifyou want to save substracted image e g so you can use imexam on it set imsave yes either using the IRAF epar or appending imsave to the command line e The z parameters are the same as those in the display task 7 Observing Practices The installation of the instrument and cables will be handled before the beginning of the run by the mountain technical staff and are not of concern to the user The SQIID Reference Manual provides coverage of the details of installation and setup for those who are interested SQIID remains on the telescope with power on under normal circumstances for the entire observing run Getting Started After SQID is installed on the telescope go through the WILDFIRE startup procedure outlined previously Once the system is operational and the detector activated check the detector and temperature stat
7. the start of the script The script dotransit modifies the do_standard script to keep the header information current To save time the do_standard script which takes five images normally shuts off the TCP info RA DEC airmass ZD after the first position and turns it back on at the end proc dotransit FER RRR KERR KEKE KKK KKK KKK RRR RRR ERE KKK KKK KERR RRR ERE RK RK KK KEKE RE RE RR KERK RT RK KK do_standard take 5 images starting at the initial position then scanning the corners of the enscribed square The telescope is returned to the initial position when done Prompts for the side of the square in arcseconds based on do_standard without turning off tcp kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk global north east if yorn Is the telescope set to the center of the field then error telescope not set make sure the coordinates are centered reset offset turn tcp header information on tcp on get size of grid puts stdout What is the separation between pictures in arc seconds set size readline puts stdout Side of enscribed square size arc seconds observe 0 0 set step l puts stdout Taking Center field go set step 2 puts stdout Taking SE field toffset expr size 2 expr size 2 go set step 3 puts stdout Taking NE field toffset 0 expr size go set step 4 puts stdout Taking NW field
8. OH airglow OH airglow thermal Note ia scattered scattered thermal components origin goes emission OG light light emission vary in intensity Conversion gain 10 10 11 11 electrons ADU Bias 600 600 700 800 mv Full well gt 200000 gt 200000 gt 200000 gt 250000 electrons in situ read noise 40 40 35 35 electrons rms pr us 21 32 197 26 electrons sec signal ee 0 84 0 84 0 84 0 11 seconds integration time The estimated limiting magnitude for S N 3 in 60 sec integration time for a point source pt mag and a diffuse source diff mag square_arcsec under average conditions temperature 50F 3mm PWV midrange OH background sans sky subtraction is summarized in Table 5 For the purposes of this calculation a 10 pixel collecting area on the sky is assumed In practice observing limits are dependent on the mode of sky subtraction employed When mapping an extended region the number of frames available for producing sky frames significantly exceeds the depth at a given position virtually eliminating the sky subtraction penalty However for the case where sky frames are exposed for an aggregate time comparable to that of the source frames sensitivity is reduced by 0 376 mag 2 5 log sqrt 2 from the values listed in Table 5 Such is often the case for deep integrations of individual fields Table 5 SQIID limiting magnitude for S N 3 in 60 sec Channel 2 1 mpt 2 1 mdiff 4 mpt 4 m diff J 19 8 20 2 21 1 21 3 H 18 9
9. activation e Enter puse parameter file to restore the parameter file active before the crash e Verify pixel_dir header dir and nextpic with plist or ped to make sure data will still be going to the desired location and will not overwrite existing data e Verify settime e Reload any scripts with the source command e Continue observing TOTALLY STALLED SYSTEM RESTART If the STALLED SYSTEM procedure fails to return the UNIX prompt or an examination of the operating processes by entering ps ax in the Console window reveals a process which cannot be halted via the kill 9 process number command it will be necessary to reboot the instrument computer In detail type fireproc or fireproc if necessary from an active window and look for the hkserv process If the fireproc task is unavailable type ps ax egrep PID wfire egrep v grep e in the Console window at the 4 m e ina Unix xgterm window logged into royal at the 2 1 m if necessary use the menu to start one Look for a control process in state D If you find such a process then e Turn the instrument power OFF before rebooting using the switch on the instrument e Reboot the instrument computer o At the 2 1m on the royal console in the computer room downstairs use the L1 A or Stop A keys then enter boot After system has returned login as telescope on the instrument computer with the current password o At the 4 m on the khaki console i
10. coadded integration move telescope n arcseconds east west n north n south n toffset e n zs z1 z2 zs00 tep on tep off movie move telescope n arcseconds west move telescope n arcseconds north move telescope n arcseconds south move telescope e arcsecs east and n arcsecs north for north east for south west set zscale values z1 and z2 for the image display enables autoscaling for the image display enable link to TCP for telescope status info and offsetting disable link to TCP for telescope status info and offsetting begin observe display loop NOTE parameters filename running number integration time coadds etc will be those of previous observation or ask routine unless specifically reset Movie frames are saved to disk and should be deleted periodically It helps to use a filename like junk when using movie Terminate movie with end CR in Instrument Control window Pay careful attention to the nextpic numbers as movie increments nextpic for only the selected channel and after movie terminates nextpic for the channels will no longer match Appendix III Troubleshooting As with all Kitt Peak instrumentation nothing is ever supposed to malfunction On the rare occasions when something seems to go wrong either by pilot error exquisite software gotchas or hardware failures recovery can in many cases be fairly simple In particular hang ups in the instrumentation so
11. correct problems FAST RESTART If WILDFIRE has been exited normally and the system is intact neither instrument power nor Heurikon DSP power has been interrupted one can simply type the following within the Instrument Control window to restore operation g sqiid The startup script will run automatically to the point where the question about array activation is presented INSTRUMENT STATUS WINDOW HAS VANISHED If the Instrument Status window has vanished first check to see if it has simply been closed Type fireproc or fireproc if necessary from an active window and look for the hkserv process If the fireproc task is unavailable type ps ax egrep PID hkserv egrep v grep e in the Console window at the 4 m e ina Unix xgterm window logged into royal at the 2 1 m if necessary use the menu to start one If the process is present the window has been closed and it will be necessary to locate and open it If the icon is not visible it may be hiding behind one of the open windows In OpenWindows one can check the windows item in the menu for the status of all operating windows if the Instrument Status window is present open it and continue observing If the Instrument Status window has died perform the SIMPLE RESTART procedure below SIMPLE RESTART If WILDFIRE has crashed Instrument Status window has vanished and could not be found by above procedures and or the hostcomputer prompt has returned to t
12. initial acquisition but stars fainter than K 9 are necessary to avoid saturation for final focus adjustments Note When SQIID is first installed it is best to start with unambiguous stars to verify initial telescope pointing Stars brighter than K 3 are best for this purpose Use individual go exposures because of the 40 second delay movie can be confusing to get the star within the central region of the array Choose a wavelength channel for determining focus preferably K which suffers least from seeing and stick with it through the run to avoid confusion The four SQIID channels are near parfocal but differences in sensitivity to seeing and slight differences in image quality away from focus can be confusing if you switch back and forth Once the star is found move the telescope until it is centered and focus the telescope resetting display limits and integration time as necessary until a tight image is obtained For optimizing focus it is best to obtain single images using observe or go and analyze the image quality with the IRAF task imexam using the r command Remember that it may be necessary to relocate the beam when moving to a new object An example of excellent focus K channel 1 0 sec can be seen in Figure 6 Note that the star appears to be positioned at the center of a pixel Since the geometric quality of the optics on the order of 80 flux within two pixels radius and the profile fitting algorithms stall near 1 5
13. on the indicator lights and follow the directions posted there Turn off the indicator lights when you are finished The 3 positions dark red polarizer yellow open green are equally spaced roughly 30 31 turns apart The hand crank can be used to move in either direction and the dark and open stations are larger than the FOV Fig 13 Cold Dark Slide hand crank and indicator Control Room Setup Inside the control room there are a number of tasks to attend to e 2 1 m only Turn on chopping secondary rack units bottom to top five in all Push MOTOR ON SERVO ON buttons on drive modules power must be on even though one is not chopping Be sure to set both the X and the Y axis source selectors to EXT ANALOG position and dial in OFFSETs for best collimated images as noted on the rack The secondary should be left ON all the time For additional information please refer to the on line 2 1 m Chopping Secondary User s Manual e Prepare object list for entry into XOBJECT cache by LTO alternatively have LTO check at earliest opportunity that coordinates sent by email are properly loaded First SQLID night only Execute obsinit to switch from ICE to WILDFIRE environment this should be done by support person e Ifitisnot already running bring up WILDFIRE on the instrument terminal and activate detector Instrument power is controlled by the switch on the instrument located on the SQIID electronics box near the power cord e Create
14. pixels this is as good as it gets FWHM of 1 8 2 0 is more typical The rightmost three values at the bottom of the profile image are the FWM from different profile fitting algorithms Naturally longer exposures will have somewhat broader profiles Fig 6 Radial image profile for excellent short exposure focus 1 sec at K Stars that are too bright will tend to be either flat topped or possibly even contain a central void as seen in Figure 7 t ae Ft rn Fig 7 Radial image profile of a star that is too bright NOTE It is likely that the single pixel events that occur at the roughly once per second are in response to alpha particles from the anti reflection coating of the last lens surface We have since discovered that thorium fluoride is the coating of choice for producing durable wide bandpass coatings The magnitude of these single pixel events is typically 3000 5000 ADU with of order 5 leakage into the four nearest neighbors Figure 8 is the radial profile for a typical single pixel event Fig 8 Radial image profile of a single pixel event At the 2 1m telescope focus is a simple function of temperature Best focus as a function of temperature shifts as deltaF deltaT 0 025 per degree K with a focus at 5 10 for 8K After the temperature of the telescope structure stabilizes it varies rapidly for roughly an hour after opening the relationship provides an accurate estimate for best focus which genera
15. settings of the lamps Within the K and PAH bands one will be dominated by the thermal emission from the dome screen and at the PAH band the lamps are not necessary Dark current and residual illumination subtraction require obtaining an identical series of observations with the flatfield lights off for J H K or the dark slide in the beam PAH After subtraction of the off or dark frame normalization using for example the IRAF response task and median combining of these observations should eliminate noise spikes or systematic features in the spectra To stay within the relatively linear portion of the array response it is preferable to turn down the lamp intensity and use exposure times relatively long in comparison to the readout time of 0 84s e g 3 5 s Keeping the flux at a modest signal level lt 5000 ADU may also help in this regard with a read noise 35 e one is completely background limited by signals gt 500 ADU The time dependent dark signal is generally small compared to the sky background for all four arrays However higher order spatial features such as the gradient on one side of the H channel are significantly brighter and cannot be neglected when contructing flatfields Dark images contain both static and time variable components with diverse causes that obviate simple scaling of dark frames to alternate integration times Consequently darks corresponding to the integration times for data that will be used
16. toffset expr size 0 go set step 5 puts stdout Taking SW field toffset 0 expr Ssize go set step 6 puts stdout Returning to starting field toffset expr size 2 expr size 2 r r puts stdout Hit return to abort Grid set il while i lt 6 eval S step i if select then break incr i turn tcp header information on tcp on puts stdout TRANSIT GRID COMPLETE The script boxS tcl does something similar to the dotransit tcl and the do_standard tcl scripts but organizes things for easier expansion One could fill a set set structure with the position increments you want to visit It is recommended that you build a series of such scripts rather than set up one that executes a massive generalized observing program in one fell swoop Note that the ask command is used to query the observation parameters only once before the observations start and provision is made for a graceful exit before commiting to the observation proc box5 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk box5 tcl does something similar to the dotransit tcl do_standard tcl scripts but organizes things for easier expansion kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk puts stdout Starting object sequence global north east zero offet parameters set north 0 set east 0 set_offset make sure the coordinates are centered rese
17. want to save in IRAF format n default is FITS cr At this point the transputer nodes will bootstrap and four tld files will load Eventually when the startup script automatically executes setup sqiid you will see messages regarding the downloading of the microcode setting of 4 values of VddCI1 1 3 VddCl2 3 5 VggCll 4 9 VggC12 2 8 and Vset 1 8 When this is completed the final message will appear Do you want to activate the array y or n y You will see messages reporting 4 biases being set followed by e The arrays are now activated If you want to use a different parameter file than the default sqiid parameter file that was executed by the startup script you can enter puse parameter_filename at this time SQIID is now ready for operation Problems If difficulties are encountered in startup entering trouble in any of the windows except the Instrument Control will open a troubleshooting diagnostic listing symptoms and possible solutions However most problems occur during the initial installation and are often hardware related The most common problems are listed below Note Detailed instructions for recovering WILDFIRE operation are contained in Appendix III red LED s in DCU halt after Configuring C004 halt after bootstrapping node 100 error 16 cannot open link cannot read telescope status Bad fiber connection With the instrument power on the g
18. window on lapis WELCOME TO THE WILDFIRE INSTRUMENT CONTROL SYSTEM This procedure walks you through a startup of the instrument control program Won non All yes no questions should be answered with a y or an n Instrument names can be typed in upper or lower case Should this procedure abort or hang during the start up please use another window to run the trouble routine This will allow you to search a TROUBLESHOOTING file to try determine why the startup failed Please mail trouble reports or suggestions for improvements to wfire lemming Press return to Continue gt Press return lt kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk If the power to the WFire DSP box in the computer rack was interrupted a hardware setup procedure must be run before it can be used This procedure must be run if the power to the DSP box went off for ANY reason Has the WFire DSP box power been off for any reason since the last time you ran startwf or restart if unsure try n n gt Press return lt kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk The Instrument hardware must be setup to allow correct data transfers between the instrument and the DSP Box This setup MUST only be done once each time the instrument is turned on Has the instrument power been off since the last time you ran startwf or restart n gt Press return lt kkkkkkk
19. 0 11 15 00 165 7 15 47 7 Channel Specific Characteristics Channel specific characteristics such as scans of the filters geometric distortion and representative bad pixel masks can be found at Supplement 1 Channel Specific Characteristics Other Preparations Object Coordinates for any epoch can be entered into the telescope computer for use during the run Although this task could be done by the telescope operator during the course of the night lengthy observing lists are best entered by electronic submission see below These may include objects standards offset and guide stars etc Acquisition of optically faint or invisible objects might require initial acquisition and coordinate updating on a nearby bright star so advance selection of these offset stars can save considerable time while observing SQIID does not use a guider Conscientious observers may send coordinate lists via email two weeks or more before the run to coords noao edu Files should be ASCII text no longer than 2000 lines Start the file with your name a cache name telescope and dates of the observing run Coordinates will be checked for format loaded into the appropriate telescope computer and acknowledgement will be sent Each object should be one line of text The format is object name RA starting column 16 or greater delimited by first blank after col 15 hours minutes seconds DEC degrees minutes seconds and epoch Each field should be separat
20. 19 7 20 2 20 4 K 18 3 19 2 19 6 19 8 PAH 12 3 13 1 13 5 13 7 Sky Background There are two predominant sources of sky background which are essentially independent both physically and spectrally The transition between the two occurs at approximately 2 3 microns Short of this wavelength the sky background is dominated by emission lines from OH in the upper atmosphere typically 90 km altitude The strength of these lines can vary over the course of the night with a timescale on the order of an hour in addition upper level winds generate inhomogeneities and overall motion of the airglow As a result the intensity of the background emission can vary unpredictably during the night Beyond 2 3 microns thermal emission from the telescope optics and sky is the predominant background This roughly follows a blackbody at 300K temperature and increases very rapidly with increasing wavelength To further complicate matters atmospheric lines primarily HO HDO CH and N O which show up as absorption features in spectra appear as emission features in the sky background so that the loss of signal and the increase in background are temperature and wavelength dependent For imaging one generally ignores the finer points and treats the longer wavelength filters like their shorter wavelength brethren when processing data One must be prepared for the simple fact that IR observations are subject to a wider range of sensitivity variations linked to chang
21. 2 ector 1 803 0 322 2 701 5 587 2 698 3 489 0 991 1 303 3 514 4 908 2 791 0 493 6 177 3 987 0 494 6 002 0 688 5 970 2 991 VSet 1 783 ISet 0 266 VDet 2 897 VDesUR 5 579 BOK 2 896 VddUC 3 475 VddOut 0 986 Vddcll 1 315 vddc12 3 545 Vggel1 4 867 Vggc12 2 773 Vp 0 489 VnRow 6 207 VnCol 3 988 VDesLr 0 494 VRowOn 5 985 VRowOff 0 685 VRstOn 5 971 VRstOff 2 991 status 3 SQIID Power supply Voltage Display Gnd Ref H K Box 0 097 Vecl H K Box 4 740 Vec2 H K Box 4 750 PRCD Card H detector 5v Sup 4 951 15v Sup 14 866 15v Sup 15 100 7v VRef 6 914 7v VRef 6 909 PA Cards H detector 5v Sup 4 952 15v Sup 14 968 Gnd Ref J L Box Vecl J L Box Vec2 J L Box K detector 4 14 15 6 6 951 906 198 921 914 K detector 4 14 950 923 J detector 4 945 14 893 15 078 6 911 6 897 J detector 4 944 14 960 0 105 4 699 4 706 L dete 1 1 L dete 1 ctor 4 944 4 922 5 250 6 906 6 897 ctor 4 947 4 804 15v Sup 15 188 15 062 15 295 15 131 5v VRef 5 002 5 001 4 992 4 992 5v VRef 4 986 4 986 4 980 4 978 H detector K detector J detector L detector voffl 0 675 0 675 0 669 0 669 voff2 0 678 0 677 0 668 0 672 Techniques Focus SQIID acts as its own acquisition camera Open up and acquire a star in SQIID Stars with K magnitude fainter than 6 are OK for
22. 7 micron pixels with 90 geometric fill factor 100 optical fill factor and a 1024 X 1024 format comprised of 4 electrically independent quadrants The ALADDIN2 ALADDIN3 readout designation corresponds to improvements in the readout design Note Table 3 reflects the array assignments within SQUID as of February 2002 The prior configuration was SCA49484_Q3 at H channel SCA41375_Q3 at K channel and SCA414107_Q3 at L channel The bias values listed are effective as of January 2005 Table 3 SQUID Arrays Characteristic J H K L Comments ate SCA 45986 SCA 46888 SCA 414375 SCA 415412 ALADDIN onic Q3 Q4 Q2 Q3 InSb Readout type ALADDIN2 ALADDIN2 ALADDIN3 ALADDIN3 version Response 5 5 5 5 within FOV uniformity en 95 95 95 85 in band efficiency Bias 600 600 700 800 mv Full well gt 200000 gt 160000 gt 200000 gt 300000 electrons lab read noise 40 45 35 35 electrons rms lapid ark signal S 0 3 0 4 0 6 0 1 electrons sec 300mv bias Conversion gain 10 10 11 11 electrons ADU Cosmetics isolated isolated reduced QE isolated primary regions pixels region pixels defects It is useful to note that dark current is a function of applied bias and because both dark current and read noise are temperature dependent in opposite senses below 40K dark current decreases with decreasing temperature to a minimum near 30K and read noise increases with decreasing temperature from a minimum near 40K they cannot both be minimized Hen
23. Computer he a a fi SSS S SSS SSS Sea SSeS eases gt g 72 AA mmj NE Fara 3 Wartyathan Wartuatkan LTO Observer 8 Fig 3 Schematic configuration of electronics and computers used with SQUD WILDFIRE Important Note The disks within the primary workstations khaki and lapis are designated datal At the 2 1 m WILDFIRE is run on the secondary workstation royal whose partition is data2 The disks are cross mounted so that access to both is possible from either machine However such cross access e g datal from royal is significantly slower than accessing the disk resident in the workstation Therefore it is imperative that the partition used for storing data taken by WILDFIRE be data2 on the 2 1 m telescope While it is possible to designate datal as the WILDFIRE data partition operation will be much slower and subject to crashes so don t do it At the 4 m one may designate either datal or data2 as the data partition WARNING Do not let the designated data disk fill up You will lose data The filenames may appear but they will have zero length The WILDFIRE housekeeping screen reports available space See Appendix VI 4 The InSb Detector Array The four detectors in SQIID are ALADDIN 1024X1024 hybrid focal plane InSb arrays produced by Raytheon Vision Systems nee Santa Barbara Research Center They consist of a photovoltaic InSb detector array mated to a silicon direct readout multiplex
24. ITS image or IRAF image headers pixel_dir mode title comment offset resetoffset filename filename ask go observe abort save ch_id display ch id east n sets path for IRAF image pixel files unused for FITS images sets operational mode for array readout stare sep sep is for observing sets title field for IRAF FITS image header sets comment line within IRAF FITS image header relative telescope RA DEC position parameter updated by TCL commanded motions reset the position offset values in the IRAF FITS image header to 0 0 sets the IRAF FITS image filename The path is is not included in filename if no argument given will prompt with current value For SQUD a d or 03d should be inserted where the picture number should be placed If no field is given 03d will be appended The format will be filename nextpic ch_id Image_extension Note when filenames conflict the saver task attempts to create a unique name by appending nnn to conflicting filename OBSERVING prompting for pre selected observing parameters initiate an observation using the previously set parameters perform one observation using current parameter set prompting for key parameters abort an observation enter in Instrument Control window follow with save include all the channels you wish to save eg j h k be sure to re issue after an abort display channel n after each
25. The SQIUD User s Manual e 1 Introduction 2 Instrument Description e 3 Command Communication and Control 4 The InSb Detector Array e 5 Observing Run Preparation 6 The IR Instrument Control System WILDFIRE e 7 Observing Practices e 8 Calibration 9 Appendices Appendix I Telescope Checklist Appendix II WILDFIRE Command List for SQUD Appendix III Troubleshooting Appendix IV Data Reduction Guide Appendix V Observing Scripts Appendix VI Cautions and Caveats Appendix VII Changes to SQIID Appendix VIII Representative WILDFIRE Interchange Appendix IX Installation Issues Appendix X ToO Observations Appendix XI FYI ooo oO 0 OO O O 0 1 Introduction The NOAO SQIID Infrared Camera Simultaneous Quad Infrared Imaging Device produces simultaneous images of the same field in the J H K and narrowband L filters using individual 512X512 quadrants of ALADDIN InSb arrays and is designed for use at the f 15 Cassegrain foci of the KPNO 2 1 m and 4 m telescopes The observations are generally background photon statistics limited The designated array for each channel is selected for characteristics read noise settling time and dark signal appropriate to background limited operation under actual observing conditions for its single filter SQIID which serves as its own acquisition camera is a good match to point and shoot observing at the 2 1 m with
26. ack in when the login window appears At the 2 I meter telescope PROPID and OBSERVER can be modified without running obsinit One can either run the newobserver command within the Wildfire Instrument Window or one can change the appropriate environmental variables within the cshrc2 file used by Royal on datal 2meter Note The SQIID instrument power supply is located on the instrument itself The rocker switch is on the right South side near the top by the power cord of the electronics box mounted on SQIID e If Wildfire is running prompt active in Instrument Control window enter exit in the Instrument Control window e Verify that the DSP power is ON Black Huericon box in computer room e Verify that the power to SQUID is OFF power supply on SQIID itself e Quit the CCD Reduction and Xintool SAOimage windows e Logout of any other IRAF processes e Enter the command obsinit ina Shelltool or Xgterm window One will be led through an interactive process o name s enter observer names o Proposal ID check the schedule or Preparation Form o Operation fire ice enter fire o Delete old data from disk and initialize y n this can take a while but to assure proper initialization you should choose y o Replace wfpar and tclSamples y n n will leave any changes After a few seconds OpenWindows will automatically load and present the login window shown below Welcome to Kitt Peak to exit
27. action on your targets CAUTION One cannot expect to simply co add observations of faint surface brightness sources and allow the off source portion of the observations within the detector FOV to determine the presumably constant level of the sky At some level defects in the flatfield pupil ghosts object ghosts or whatever dominate the accuracy of the results This deficiency is typically overcome by subtracting off source observations of the sky then flatfielding the differences This improves the accuracy of the detected signal by at least an order of magnitude In the IR even at JHK observations of all but the brightest stars 9 mag are background limited so that typical diffuse targets such as galaxies are seen at very low contrast in individual frames As noted above the sky background is constantly changing slowly with airmass and on slow to moderately rapid timescales with sky emission so that the contrast varies as a function of time Since observations are ultimately limited by inadequacies in the flatfield one cannot simply co add such observations and obtain a meaningful result median filtering such data merely selects the middle frame For example as the contrast varies the illumination pattern on the array also varies since the relative mix of radiation seen through the telescope optics and that seen directly past the secondary changes One must devote a comparable amount of time off source intermixed throughout the o
28. and the header and pixel directories Observing Parameters title IRAF header title coadds number of coadded integrations per image Inrs number of low noise reads 1 for SQIID pics number of pictures per observation integration_time filename integration time seconds IRAF filename header_dir image header directory pixel_dir pixel file directory mode process mode stare sep hphot nextpic picture index ucode microcode display channels to display j h k or 1 for SQIID ra RA of object dec DEC of object epoch epoch of object offset observation offset imag_typ type of observation object dark flat airmass airmass of object comment comment im_list filename of image list save channels to be saved to disk j h k I or subset for SQIID archive channels to be archived j h k 1 or subset for SQIID WARNING Use set time to set coadds and integration time rather than responding to the individual coadds and integration time queries from ask In general the parameters fall into three categories e those which one may wish to modify for an observation integration time title e those which one might want to change on an infrequent basis comment header directory e those which are never changed mode display or are automatically entered into the header through the link to the TCS computer marked with above The command ped will open an editing session on the curren
29. ao edu 520 318 8319 We will define a dataset to be the set of direct observations of a given field These may be dithered observations of a single target or a mosaic of a larger region In the extreme case the dataset may contain only a single exposure and only steps A and B listed below would be required The basic path for the reduction of SQIID dataset can be described as follows Create DARK FLAT and SKY frames for each channel e Process each individual source frame to remove instrumental dark current sky background and pixel to pixel sensitivity variations Combine all images of a given target into a database e Interactively define the relative spatial offsets between each image in the database for one of the channels Combine the images in the database into a single image suitable for analysis using bad pixel masks to exclude bad pixels Users are cautioned that IR image datasets often present a greater data reduction challenge than optical CCD images both due to the superior performance of optical CCD detectors lower dark current readout noise and pixel to pixel sensitivity variations and especially due to the extreme background limited nature of most IR observations The results at each step in the process should be carefully examined and problems understood before proceeding Many problems can be solved by the exclusion of bad images from the datasets The upsqiid IRAF package is contained within a tar file ca
30. been off for any reason since the last time you ran startwf or restart if unsure try n n y e Was the computer rebooted with the instrument power off n y a short initialization process follows e Has the instrument power been off since the last time you ran startwf or restart n y e Is the instrument power on now n You will be prompted to turn on the instrument power cr Which instrument are you using enter PHOENIX IRIM CRSP SQUID etc IRIM The instrument name may now be in either capital or lowercase letters Do you want windows y cr Do you want to save in IRAF format n default is FITS cr At this point the transputer nodes will bootstrap and tld files will load Eventually when the startup script automatically executes setup irim you will see messages regarding the downloading of the microcode setting assorted voltages When this is completed the final message will appear e Do you want to activate the array y or n n You will see messages about assorted voltage failures and servo errors since the IRIM task looks for DACs and for motors that SQIID does not have but the housekeeping window and the saver task should successfully start wow Go to the Instrument Control Window and exercise the system by typing status s status v and status t then exit the system by typing exit Continue by typing g phoenix Answer the questions Do you want windows y cr D
31. c roughly fixed e Mode of array operation mode dependent It takes time to move the data from the instrument through the distributed hardware out into storage on the Sun Workstation During this time critical resources are involved which do not lend themselves to overlap reuse so that the start of a new integration must be held off until the pipeline is clear For an externally realized integration it currently takes 40 seconds following the last readout to safely deliver the results Since the actual disk write time is but a fraction of this total little time is to be gained for example by electing to not save undesired channels to disk The preferred method for improving observing efficiency involves internal co addition since co addition of JHK frames entails an overhead of only 10 millisec By co adding integrations to produce the equivalent of a l to 3 minute integration the effect of data pipeline flow overhead is minimized The mode of array operation also has a significant impact on observing efficiency In particular it is important to understand the role of minimum JHK integration time in the JHK observing efficiency SQIID currently employs global reset and double correlated sampling to produce an image each image is the difference between two reads of the array and the minimum integration time is roughly the time to read the array once Consequently at the shortest integration times approaching the minimum integration time of o
32. ce the array operating temperature is generally selected to provide an application background specific compromise Further information on the array design and operation may be found in Fowler et al Proc SPIE 2268 340 345 1994 and in Fowler et al Proc SPIE 2816 150 160 1996 The multiple correlated sampling technique used for read noise reduction is described in Fowler and Gatley Ap J Letters 353 L33 1990 Telescope performance is covered in Section 5 The relatively high dark signals listed in Table 4 which do not compromise performance are indicative of compromises in the instrument design not intended for low backgrounds the need to operate at high bias and the freedom to deploy specific arrays that might be unsuited to more demanding applications 5 Observing Run Preparation The limiting performance of SQIID depends on a number of factors System Responsivity Typical observed fluxes for a 10 0 magnitude star at the 2 1 m telescope are listed in Table 4 By direct measurement the fluxes are a factor of 3 21 higher at the 4 m telescope and the sky background per pixel is essential the same The conversion gain is a detector specific 10 11 electrons ADU Note the biases listed are not necessarily the current bias values Table 4 SQIID Performance on 2 1 m channel J H K L comments JE er 3 25e4 2 9004 1 78e4 ADU sec within aperture Sky brightness lg 421 387 227 ADU sec pixel level Sky brightness OH airglow
33. computer instrument and Heurikon DSP power ON at all times Appendix II WILDFIRE Command List for SQUD SQIID image names follow the naming convention filename ch_id XXX image_extension e g nI 001j fits where filename is an observer controlled parameter ch id is the approripate designator from the set j hk 1 the number XXX is sequentially numbered being automatically incremented for each exposure until a new value is declared either at a new object or new night and image_extension is either fits or imh depending on the saver setting declared at startup If you correctly set oldirafname yes when reading the data from tape the image names will be restored to their original names and match the log sheets A list of available commands within the WILDFIRE instrument control window is commands command ed name help name man name progress 0 source program activate deactivate setup sqiid SYSTEM LEVEL execute the commands in csh or run csh give help on a command call up an editor on a proc display help for one of these topics display a man page for a given topic minimize diagnostic output during integrations node temporarily include tcl program within recognized system need to source again after powerup or go full path name required DETECTOR activate the detector deactivate the detector set up the default SQIID voltages and prompt for activa
34. d lt setup sqiid Min time for j 0 61 Min time for h 0 61 Min time for k 0 61 Min time for 1 0 061 L Integration Time 0 321 L coadds 1 JHK Integration Time 0 321 JHK coadds 1 seq Stopped here 0 128 256 384 512 640 768 896 1024 1152 1280 1408 1536 1664 1792 1920 2048 2176 2304 2432 2560 Min time for j 0 61 Min time for h 0 61 Min time for k 0 61 Min time for 1 0 061 running Please wait while voltages are set setting Vddcll Array 0 VddCll 0 set to 1 306 Array 1 VddCll 0 set to 1 319 Array 2 VddCll 0 set to 1 323 Array 3 VddCll 0 set to 1 300 setting Vddcl2 Array 0 VddCl2 0 set to 3 518 Array 1 VddCl2 0 set to 3 551 Array 2 VddCl2 0 set to 3 576 Array 3 VddCl2 0 set to 3 513 setting VggCll Array 0 VggCll 0 set to 4 881 Array 1 VggCll 0 set to 4 870 Array 2 VggCll 0 set to 4 892 Array 3 VggCll 0 set to 4 921 setting VggC12 Array 0 VggCl2 0 set to 2 785 Array 1 VggCl2 0 set to 2 797 Array 2 VggCl2 0 set to 2 786 Array 3 VggCl2 0 set to 2 791 setting VSet Array 0 VSet 0 set to 1 784 Array 1 VSet 0 set to 1 790 Array 2 VSet 0 set to 1 810 Array 3 VSet 0 set to 1 816 Do you want to activate the array y or n y gt Enter y lt Note n is the safe value However one must type y to get the arrays properly activated The detector biases may vary from those indicated set to set to Bias Bias Detector Detec
35. dix V TCL Scripts Scripts are a powerful tool for executing a sequence of tcl commands including telescope motions instrument motor commands and observations as a single executable program Many of the wildfire commands are simply protected scripts within the wfire tcl directory Observers may generate their own scripts in the public directory data2 telescope tclSamples One approach is to browse through the existing scripts to find one that performs a function similar to that desired copy it to a new file and edit it as required It is important to note that the first line contains the base name of the script and must be edited to reflect the new name of a script created in this manner Scripts copied into the user home script directory data2 2meter wfire at the 2 1 m and data2 4meter wfire at the 4 m and sourced can be marked for automatic inclusion in subsequent invocations of startwf by entering mkIndx Below is a typical script dotransit used with SQIID This will take 5 observations one at the center and four corners of a box This script employs a string array setup by the set step lines to hold the commands which are run within the while loop After each step the loop recognizes a CR as a signal to abort the script leaving the telescope pointed wherever it was Since the reset_offset command zeroed the north and east position variables these variables accurately report the current position relative to that at
36. do standard takes 5 observations in a fixed spatial pattern using the current parameter set for integration time filename etc First observation is at the current position next four are in a square centered on the first position routine then repositions the telescope to the starting position and quits You are prompted for the side of the square in arcseconds Verify that your objects do not systematically land on bad pixels if they do change the initial point or offset value Note script updates the telescope information in the image header on the first image using tcp_on and then turns header updates of telescope information off using tcp_off for the rest of the sequence After the last image is taken telescope header updating is restored using tcp_on e do standard on same as do standard but updates telescope information in the image header for each image in the sequence e do field observe an M x N RA x Dec spatial grid of positions with fixed separation E W and N S using the current parameter set Returns to starting point when completed The grid is centered on the starting position Prompts for the number of grid positions E W the number N S and the grid separation in arcsec Observations begin at NE corner proceeding W and S a row ata time The command line version is do fld ewnum nsnum gridsep e do dither observe an M x N RA x Dec spatial grid of dithered pairs with fixed separation EW and NS using th
37. e Instrument Control window the hostcomputer prompt will return e When you see the hostcomputer prompt in the Instrument Control window proceed with the SIMPLE RESTART procedure above TOTALLY STALLED SYSTEM QUICK RESTART If the STALLED SYSTEM procedure fails to return the UNIX prompt or an examination of the operating processes by entering ps ax in the Console window reveals a process which cannot be halted via the kill 9 process number command it will be necessary to reboot the instrument computer In detail type fireproc or fireproc if necessary from an active window and look for the hkserv process If the fireproc task is unavailable type ps ax egrep PID wfire egrep v grep e in the Console window at the 4 m e ina Unix xgterm window logged into royal at the 2 1 m if necessary use the menu to start one Look for a control process in state D e Reboot the instrument computer o Atthe 2 1m type freboot on Royal s console VT220 or whichever terminal is currently attached to royal in the computer room downstairs o At the 4 m use the L1 A or Stop A keys then enter boot After sytem has returned login as telescope on the instrument computer with thecurrent password e In the control room go to the Instrument Control window and type g sqiid The startup script will run automatically to the point where the question about array activation is presented answer y to question about detector
38. e current parameter set Two frames slightly offset dithered EW are taken at each grid location Grid is centered on the starting position and returns here when done Prompts for the number of grid positions E W number N S grid separation in arcsec and E W dither in arcsec Observations begin at NE corner and proceed W and S a row at a time The command line version is do_dthr ewnum nsnum gridsep dither e do pair take a pair of spatially offset images and return to the first position This is particularly useful to confirm the location of a faint object which can be determined by subtracting the two frames Prompts for the offset vector in arcsec and must receive two values RA first then Dec separated by a space Use to specify E and N for W and S The command line version is pair ewsep nssep e do 9raster observe a3 x 3 spatial grid of source and dithered offset sky data pairs in the sequence source sky sky source The sky position is dithered between each sky frame so that objects in the sky field are not position locked relative to the source frames The data are taken in an order which minimizes telescope motions Note script updates the telescope information in the image header on the first image using tcp_on and then turns header updates of telescope information off using tcp_off for the rest of the sequence After the last image is taken telescope header updating is restored using tcp_on Promp
39. e from linearity in terms of the relative error input observed or the normalized relative error input observed observed for each array and fits these data to an appropriate mathematical model For SQIID the model fitted function for the relative error is ym x a 1 x 2 a 2 x 3 where ym relative error input observed x observed adu The fit is valid for values lt Xmax For values beyond Xmax the array is rapidly approaching saturation The fitted parameters for each channel are summarized in Table 10 and the fitted linearity is plotted in Figure 12 A new array was installed in the H channel in February 2002 Table 10 Fitted Linearity Coefficients Valid from Jun 2000 Jan 2005 Jan 2005 Mar 2002 Jun 2000 Jun 2000 Channel bias Ks 700mv H 700mv J 700mv H 600mv J 600mv H 600mv a 1 6 4864e 7 1 3456e 8 1 2626e 6 8 4783e 7 1 2164e 6 4 5326e 6 a 2 4 4790e 10 6 1010e 10 2 9498e 10 6 8416e 10 4 7829e 10 4 8759e 10 Xmax ADU 16000 16000 16000 16000 16000 14000 Data date Apr 2003 Apr 2003 Apr 2003 Apr 2003 Apr 2003 Apr 2001 SQIID Relative Error 0 20 Ks 700mv J 700mv g J 600mv 8 0 15 H 700mv Q H 600mv 0 10 un DO B 0 05 lt 0 00 0 5 102 1 104 1 5 104 Observed ADU Fig 12 Linearity Correction for SQUD Relative error for H green K red and J blue Channels for 600mv and 700mv bias Conver
40. e s enter observers here o Proposal ID check the schedule or Preparation Form o Operation fire ice enter fire o Delete old data from disk and initialize y n this can take a while but to assure proper initialization you should choose y o Replace wfpar and tclSamples y n n will leave any changes Once this is complete it is necessary to reboot the instrument computer with the instrument power off e Atthe 2 1 m type freboot at the login prompt on Royal s console VT220 or whichever terminal is currently attached to royal in the computer room downstairs At the 4 m use the L1 A or Stop A keys then enter boot After rebooting the UNIX login prompt hostcomputer login will appear IGNORE THIS After a few seconds OpenWindows will automatically load and present the login window shown below Welcome to Kitt Peak to exit Login Password Login as telescope where telescope is 2meter or 4meter as appropriate with the current password posted on the workstation terminal The WILDFIRE system will then load automatically resulting in a terminal screen layout approximately like Fig 5 below the dashed window labeled Instrument Status will appear in the approximate position shown only after the instrument microcode has been loaded Normal WILDFIRE Startup The Windows Once the environment has been set to WILDFIRE by obsinit it will remain in that state even if it is necessary to reboot
41. ed by one or more spaces NO TABS the delimiter in the RA and DEC fields may be spaces or colons Example e alpha nuti 12 34 56 7 89 59 59 9 1734 4 Further details may be found in the June 1992 NOAO Newsletter or the new Observers Handbook Standards are a subject of continuing discussion and probably will remain so for some time For the purposes of determining and removing the effects of telluric absorption and throughput in the instrument it is desirable to observe a calibration star as near as possible to the object in both space and time Owing to its high sensitivity and relative coarse pixel scale SQUID must be calibrated using standard stars fainter than JHK 9mag Recent compendia of faint standards are extremely useful in this regard A New System of Faint Near Infrared Standard Stars by S E Persson D C Murphy W Krzeminski M Roth and M J Rieke in Astron J 116 2475 2488 1998 Northern JHK Standard Stars for Array Detectors by L K Hunt F Mannucci L Testi S Migliorini R M Stanga C Baffa C F Lisi and L Vanzi in Astron J 115 2594 2603 1998 JHK standards for large telescopes the UKIRT Fundaental and Extended lists by Timothy G Hawarden S K Leggett Michael B Letawsky David R Ballantyne and Mark M Casali in mon Not R Astron Soc 325 563 574 2001 Visitors should arrive on the mountain at least by early afternoon of the first night This will allow time to become familiar w
42. efore beginning the next nights observing e When restarting the WILDFIRE System the default sgiid parameter set may not load the preferred microcode sqiid4d 2233 03 After the setup sqiid task has completed one can check the microcode using ucode and download the proper code with dl sqiid4d_2233_03 Appendix VII Changes to SQUID During February 2002 the final planned upgrades to SQUID were installed The relative spatial orientation and offset amongst the channels has changed and channel characteristics will need to be re determined The changes are summarized as follows e New masks designed to redirect the images on the mask away from the array were placed in front of the arrays e Within the K channel the Barr K filter was exchanged for a OCLI Ks K filter of the type used in FLAMINGOS and TIFKAM MOSAIC Despite the 12 decrease in bandpass the improvement in transmission and the lower thermal background of the Ks filter should improve limiting performance by about 0 2 magnitudes The K channel array was rotated 180 degrees to remove the diagonal crack from the FOV It was judged that the small region of reduced QE about 10 lower near the NW edge of the field in Q2 was preferable to the diagonal crack in Q3 The crack in Q3 was difficult to remove by dithering e Following the official closure of the highly successful ALADDIN Consortium involving NOAO USNO Flagstaff and Raytheon Vision Systems the ownership of specif
43. elength so that their in band transmission and out band reflectivity is very high Since each camera is designed for optimum performance over a limited wavelength range the AR coatings provide unusually high transmission The opportunity for optimizing each channel for operation over a restricted wavelength compensates for transmission losses within the dichroic system and has yielded high throughput in all channels comparable to that of a single camera system SCOPE LIGHT METER KES Ch ree n gt on mae dr hodt ot Geer IER INCOMING TAL kn bk ANE bl i pocos ae ur maxs ee Ser Ree ha J DION si 1 s j i d j 4 1 T Pr T MORJE 09 t JP 1 me BAND BAND PASS fiLIO e 4 0 9 pa sr LY TF PE r E _ a t 4 L rte BAND eie Figure 1 SQIID Optical Schematic Fig 1 Optical layout of SQUD The elements are identified in the text SQUD which was built in an era where 58X62 was standard and initially deployed 1990 1995 with 256X256 Platinum Silicide arrays was designed to smoothly accommodate larger devices The optics was designed to illuminate a 512X512 array of 25 micron pixels Since the ALADDIN array has 27 micron pixels some vignetting is inevitable In addition upon seeing the full FOV for the first time we discovered some unintended vignetting in RA within the instrument that would require a substantial effort to rew
44. er via indium bumps The readout is a p channel MOSFET device The ALADDIN array was cooperatively designed and developed at RIO SBRC with the ALADDIN Consortium consisting of NOAO and the US Naval Observatory Flagstaff The device is presently operated in a non destructive readout mode providing double correlated sampling A representation of the voltage on a single pixel during an integration and readout is shown in Fig 4 An address cycle consists of a reset to the canonical detector bias voltage a non destructive read followed by a second read During the reset operation the voltage on each pixel is set to the value Vg When the reset switch is opened the voltage left on the sense node will differ slightly from Vp due to charge spillback from the reset gate and from kTC noise After a time fdly the voltage on the pixel is sampled nondestructively i e without resetting yielding V After a second time interval defined as the integration time the voltage is again sampled yielding V The signal is the difference between the two reads Note that this technique known as double correlated sampling eliminates the effect of the transient following the reset operation The intervals indicated not to scale at the bottom of Fig 4 represent the time required to carry out each operation on the entire array thus on an absolute frame the time at which a given pixel is reset and read depends on its location in the array Non de
45. ettings one for J H and one for K should suffice The high background at L band obviates dome flats use sky L band flats instead Use an illumination level sufficient to give approximately 5000 ADU in 2 s integration time Higher signals in shorter integration times may exacerbate nonlinearity effects Read noise is sufficiently low that 200 ADU signal will be background limited Obtain 5 10 flats in each band desired for later median averaging Turn flatfield lights off and obtain an equal number of non illuminated bias images at each setting Compare flatfield and dark current data with standard frames as check on array performance Look at IRAF FITS longheader to verify that telescope coordinate information is being acquired Final Setup at Start of Night Telescope Operator will do final dome and telescope checks and acquire stars offset etc SQIID acts as its own acquisition camera e Acquire ephemeris star K 9 10 Ensure telescope focus is near nominal value 5 20 at 2 1 m 7500 at 4 m e Acquire center and focus infrared image resetting zs and integration time if necessary e When satisfied zero telescope pointing Observing Miscellany Telescope motions are generally commanded from LTO terminal although they can also be entered from the observer s terminal For programs demanding frequent motions agree on a mutually compatible protocol with the LTO In the event of multiple observers only one should serve as the commu
46. etween exposures and deriving the median of the individual observations True dark frames are generally not necessary in the course of normal observing since sky subtraction removes the dark current as well and flatfield exposures except for L are best done by cycling the illumination lamps on and off Most importantly the strong and variable background requires that sky subtraction be handled in a two step process First order sky subtraction is achieved by subtracting a sky frame The very high level of IR sky brightness precludes the traditional CCD approach of flatfielding and background reduction on a single object frame since even a uncertainty in the flatfield would produce effects large in comparison to the object signal The first order sky subtraction will typically remove 95 99 of the sky thus greatly reducing the effects of flatfield uncertainties in the second order background removal The majority of experience with SQHD has been in the J H and K bands where the background consists of OH and O lines superposed on the spectrum Beyond 2 3 microns the background consists of a smooth continuum due to the emission from the telescope as well as emission lines in telluric features Thus transitions that produce telluric absorption lines in astronomical spectra will produce emission lines in the sky background Although this scenario is more challenging the same routines of sky subtraction and off object residual background sub
47. f the array entering spacebar will prompt you to move the cursor to the target position and enter another spacebar In either case the computed offsets will be displayed in the IRAF window The displayed offset command toffset may be pasted directly into the Instrument Control window Michael Merrill s provisional IRAF script idisp may be used to display sky subtracted images in the ximtool window Because this is not yet a standard IRAF task it will probably have to be manually installed for an observing run The script is defaulted for SQHD at the 2 1 m The parameters are as follows first_image test010j fits First image in sequentially numbered images sky_image 1 Name or sequential number of sky frame frame 2 Display frame number_id 000 image number template results image 000 listid tmp list name of wildfire system image list dolast no Repeat for most recent image dostats yes Perform imstats statsec 100 400 100 400 Image section for calculating statistics lthreshold INDEF Lower threshold for exclusion in statistics hthreshold INDEF Upper threshold for exclusion in statistics imsave no Save difference of each pair saveid dpr_ String prepended to object name zscale yes automatic zcale on each frame ztrans linear intensity transform log linear none zl 0 minimum intensity z2 1000 maximum intensity e To execute enter idisp
48. for defining flatfield and linearity issues should be taken A sequence of 9 exposures should be sufficient Since the dark current is so low you will be able to see transient events such as those due to cosmic rays that can be removed by median filtering Darks should be taken in the afternoon and or in the morning Closing the cold internal darkslide hand crank on the side of the instrument is both necessary and sufficient for taking darks The time dependence of the median dark current within 100 400 100 400 is shown in Figure 11 Note that the H channel exhibits an apparently negative dark current at short integration times SQIID Dark Current 700mv 500 Ks channel A J channel 400 x H channel 2 z 300 200 5 O x 100 a 0 0 10 20 30 Integration Time sec Fig 11 SQIID dark current for H green K red and J blue Channels at 700mv bias Conversion gain is approximately 11 electrons per ADU Sky Subtraction While the detectors are stable the sky is not necessarily so Under good conditions sky flux varies only with airmass and at a given position the sky can be stable over an hour or more Naturally sky flux increases when you get near the moon When airglow is high and variable the sky at H can vary by a factor of two over the course of an hour while the sky at J varies by 40 Consequently it is prudent to monitor the sky use imstat inside IRAF to be sure that you have sufficient data to perform sky subtr
49. from the entrance window which is shared in common permitting high efficiency AR coatings to deliver high instrumental throughput The four separate channels are co focused and co aligned with a minimum overlap region of roughly 500X500 pixels common to all channels and are physically edge masked to stop stray light from entering or leaving the readout The detectors are of sufficiently high quality and uniformity that the dark sky subtracted raw data are useful in assessing data quality in near real time Detector area stability uniformity quantum efficiency low read noise and dark signal combine to make SQIID the system of choice for any observation which requires multi color JHK imaging over large areas of the sky quick look at transient targets and for deep observations of selected regions IR observations of necessity consist of sequences of frames with interspersed telescope motions Each set includes a subset of small telescope motions dithering to dodge bad pixels and provide better image sampling and may require equal time spent off target especially when observing extended sources and or crowded fields Typically the minimum time spent on taking a complete set of frames at a given field within detector FOV can be on the order of 10 minutes or more With a single channel imager the same set of pointings needs to be repeated for each filter Since variations in observing conditions seeing airmass sky transparency and atmosphe
50. ftware can usually be corrected without resorting to rebooting the computer which should be considered a last resort The following tables cover situations that may arise with the Instrument Computer or SQIID itself Some situations are not covered in this manual since the recommended recovery could involve procedures that are potentially harmful if done incorrectly In these cases the user is requested to call for technical assistance from the Observatory staff no signal minimal signal at J H large signal at K apparent vignetting bootstrap failure Instrument Hardware Internal cold dark slide closed Check status s for proper temperatures voltages Check that green LED in analog electronics box is lit If the detector has been accidentally deactivated program will not sense this observe will work but return pixel values near zero in image Telescope mirror covers dust slide top South and or external dark slide pull knob at NorthEast closed Check status s for proper temperatures voltages External darkslide may be partially in place or internal aperture wheel may not be set to open position Vignetting by external darkslide or dust cover will elevate K background If the internal polarization anaylzer is in position the image will be vignetted on all sides with half the signal Vignetting also results in higher backgrounds in the K and L channels If the startwf procedure fails during the bootstrapping node
51. get a listing of the process numbers then kill 9 process and then entering saoimage amp to bring up the SAOimage window e 5 Console This is generally used only for diagnostic or emergency purposes such as killing a hung process or the entire WILDFIRE when it hangs up Bringing up WILDFIRE There are three basic steps in the complete startup of WILDFIRE hardware initialization starting WILDFIRE instrument initialization The procedure below will go through all three steps as would be necessary on the first night the instrument is on the telescope Hardware Initialization This procedure establishes the link between the DSP box and the computer by rebooting the observer s SUN workstation with the SQUD power off The obsinit procedure for the first night of an SQIID block described above includes these steps Starting WILDFIRE the first night NOTE When starting SQUD the first night we have found that it is important to thoroughly exercise the Wildfire distributed memory by bringing up IRIM then PHOENIX and finally SQUID The following sequence walks you through this task At this point the windows should be present as in Fig 5 Go to the Instrument Control Window and enter startwf This will lead you through an interactive startup procedure READ THE QUESTIONS CAREFULLY simply entering cr will return the default which may not be appropriate For the full startup the replies are e Has the WFire DSP box power
52. he 4 m is well back from the nominal focal plane of the telescope a re imaging lens in each guide probe assembly permits them to be used for guiding and precision offsetting Instrument Rotator Pull Knob Dust Cover Warm Dark SQUD MOUNT Pull Tab Side an Hand Crank Rocker Cold Dark Power Switch i SQID DEWAR ee age av Air Hender 5 Hose le SQIID ELECTRONICS L__ 1 POWER SUPPLY Power Communic ations vo Oo Indicator Lights Optical Fiber 4 active Fig 2 Side View of SQIID SQIIDs temperature is maintained by a pair of Closed Cycle Cryogenic Coolers that employ pressurized helium gas as a refrigerant Most of the internal parts including the dichroics optics and filters are cooled below 70 K with the first stage of the Closed Cycle Cryogenic Coolers Each array is operated at 30 K by a thermal strap to the second stage of the Closed Cycle Cryogenic Coolers plus a closed loop heater circuit Refer to Fig 2 to identify the external features of the instrument SQIID will be cabled upon installation and should not be uncabled for any reason without contacting KPNO staff first The only necessary user contacts with the focal plane instrument are the instrument power switch located on the electronics box and the mechanisms for inserting the internal and external dark slides 3 Command Communication and Control SQIID operates through a distributed computer network
53. he Instrument Control window the following steps within the Instrument Control window should restore operation e Ifthe prompt is present first enter exit to cleanly exit the processes and get the hostcomputer prompt e At the hostcomputer prompt enter g sqiid answering y to question about windows note CAPS e Enter puse parameter file to restore the parameter file active before the crash e Verify pixel dir header dir and nextpic with plist or ped to make sure data will still be going to the desired location and will not overwrite existing data e Verify settime e Reload any scripts with the source command e Continue observing NOTE If the power to the instrument and or the Heurikon DSP box in the computer room has been interrupted or the computer has been rebooted this procedure may not be sufficient See below for more specific procedures STALLED SYSTEM RESTART If WILDFIRE is hung Instrument Control window unresponsive won t respond with a system prompt after issuing a CR and data collection stalled e Enter AC AC in the Instrument Control window Enter hung several times o at the 4 meter in a Unix xgterm window logged into khaki rlogin khaki o atthe 2 1 meter in a Unix xgterm window logged into royal rlogin royal until either the WILDFIRE prompt or the UNIX hostcomputer prompt returns in the Instrument Control window Ifyou see the prompt first type exit in th
54. ic arrays was determined As a consequence the H and L channel arrays in SQIID were exchanged for more appropriate devices The new H channel array has better cosmetics no cracks and the new L channel array has higher well capacity than their predecessors e Anew Lyot stop with central obscuration intended to reduce the background was installed in the L channel Appendix VIII Representative WILDFIRE Interchange Starting WILDFIRE The following session is representative of starting up a WILDFIRE session with SQIID Actions on the part of the observer are set apart in bold type inside square brackets gt Enter commands here lt where one types the enters the quoted text at the keyboard followed by a carriage return Informational asides are set apart in bold Note WILDFIRE presents choices as bracketed values n where the default value selected by answering with a return is the value inside the brackets The proper answer to yes and no questions is y or n not yes no etc Generally the boolean values are defaulted to the most likely value gt In the Instrument Control window type startwf lt lapis startwf royal being added to access control list 1 18486 2meter lapis stty TCGETS Operation not supported on socket 1 27884 2 27885 Note at this point control passes to WILDFIRE At the 2meter a new Instrument Control window running remotely on royal overlays the Instrument Control
55. iciently and gracefully cleaning the disk of data from previous observers Storing the current observer name and proposal number for archiving First Night of SQUID Block On the first night of an IR block the ICE environment will still be active the presence of the CCD Acquisition and CCD Reduction windows will verify this It will be necessary to run obsinit to change to the WILDFIRE environment as well as for the other reasons above since the hardware may be in an unknown state it is also recommended to run through a complete hardware initialization on the first night of an IR block as part of the obsinit process This will involve rebooting the observer s SUN workstation with the DSP in the computer room powered on and the SQUID instrument power off The First Night procedure is detailed within Appendix IX Installation Issues Since this procedure differs both in complexity and detail from the situation normally conforting the observer we will not recount it here New Observer The following assumes that the change from ICE to Wildfire has already occurred and that Wildfire is already running properly On subsequent SQIID runs obsinit is run only to enter the new observer and proposal ID information It is NOT necessary to power down SQIID or reboot the computer After typing exit in the Instrument Control window and logging out of all IRAF processes and running obsinit simply exit OpenWindows from the desktop menu and log b
56. iform external illumination source The background in the IR results in sky levels with S N of better than 100 in a single 3 minute exposure By taking the median of a reasonable number of blank fields or target fields without large objects obtained at different times during the night and at different locations on the sky a satisfactory measure of the system flatfield can be derived Generally DARK frames taken with the internal cold dark slide in place are stable over a night at about 1 electron sec and are probably stable over an entire observing run Changes in dark current can accompany changes in the ALADDIN array temperature Since the SQIID dark current has both a base level and a time dependent component a dark frame must be created for each exposure time that you intend to use to determine flatfields or for dark subtraction during the observing run it is assumed here that the observer has obtained such dark exposures BRIGHT STAR One may define a bright star as one that can be observed in frame times of less than 10 s in this case the greatest limitations to S N are systematic effects rather than background limited statistics To overcome these set coadds to 3 5 to build up signal to noise on each frame and take 5 7 observations of the star displacing it between observations The do_standard script is ideal for this operation Since the observations span a short time the sky will not vary significantly and one can genera
57. ing environmental conditions OH airglow and temperature than the optical where phase of the moon and sky transparency predominate Table 6 estimates the relative sensitivity for SQIID for three levels of OH airglow Table 6 Estimated SQIID performance variation with OH airglow Airglow J H K L Comments low 0 25 0 25 0 08 0 00 magnitudes improvement medium 0 00 0 00 0 00 0 00 magnitudes improvement high 0 24 0 20 0 10 0 00 magnitudes improvement Estimates of the relative background and sensitivity variation for SQUD for three different ambient temperatures and 4 values of Precipitable Water Vapor are summarized in Table 7 and Table 8 respectively At KPNO Imm PWV is a winter rarity and 9mm PWV is a Monsoon Season staple It is useful to remember that the thermal background comes from both the atmosphere which varies with airmass and the telescope which does not vary with airmass in comparable quantities Although observations at JHK are onscale under all conditions at high temperature the L channel can saturate and become unusable The primary symptom of saturation is an East West gradient in the L background at the shortest integration times If one desperately needs to perform L channel observations under higher temperature conditions insertion of the cold internal polarizer element it is the third choice in the open dark polarizer position controlled by the hand crank on the instrument drops the background and the signal
58. ith the instrument create and test observing parameter sets and enter object coordinates into a cache First time users of SQIID may wish to arrive a day early and spend some time in the evening looking over the shoulder of the previous observer with his her prior permission 6 The IR Instrument Control System WILDFIRE Note This contains a SQIID specific synopsis of the WILDFIRE manual written by Nick Buchholz Interim notes for operation at the 2 1 m telescope As of December 2006 the SQUID operating environment at the 2 1 m telescope has changed with the incorporation of a Linux based workstation as the console for operations in the control room e The two monitors along with keyboard mouse that used to belong to lapis now connect to sapphire a Red Hat 9 Linux machine The monitors are in Xinerama mode which produces a display w that seamlessly spans the two monitors Login and password are as before i e user 2meter etc Both apis and royal reside with their monitors and keyboards in the computer room e Access to lapis is via VNC Clicking on the VNC icon on the menu bar at the bottom of the left hand sapphire screen opens the X 1 desktop on lapis without a need to enter a password After lapis reboots and after an obsinit this desktop automatically opens the Instrument Control Window Please note that people can access this desktop from ANY machine on NOAO network e g if an observer has a laptop connected to the 2 1 me
59. kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk The Instrument hardware must be setup to allow correct data transfers between the instrument and the DSP Box This setup MUST only be done once each time the instrument is turned on Has the instrument power been off since the last time you ran startwf or restart n gt Press return lt kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Which instrument are you using enter PHOENIX IRIM CRSP SQIID etc SQIID gt Enter SQIID lt kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Do you want windows y type n if not using X windows gt Press return lt kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk Do you want to save in IRAF format n default is FITS gt Press return lt FITS fits Note at this point WILDFIRE bootstraps the system sldnet noio SQIID LD NET Network Loader Version 89 1 Link I O Driver SCIO Copyright c 1986 1989 by Logical Systems Loading first phase of bootstrap to root node 1 Finished loading first phase awaiting first acknowledge Loading second phase of bootstrap to root node 1 Bootstrap loaded awaiting acknowledge Successfully bootstrapped root node 1 Note If there are problems either establishing or linking with the root node the system hangs or exists here Hangups during Bo
60. le a series of observations in the dark filter immediately following sky or dome flat observations will show a monotonic decrease in mean value as the memory of the relatively bright preceding observations decays over 5 to 10 integration times By the same token a series of dome flats following dark or low background observations will show a monotonic increase in mean value as the memory of the higher flux observations accumulates One possible approach is to take a larger number of dome flat or dark observations and reject those early in the series when the change in value from one frame to the next is the greatest Should one decide to obtain dome flats it is recommended that one take exposures when the dome is dark to minimize the ambient radiation at J and H At the 2 1 m and 4 m telescopes the dome screen is illuminated by lamps mounted on the telescope top ring The 4 m telescope is positioned by mountain technical staff Darkening the dome may require waiting until visitor hours end at 1600 hr The lamp controls at these telescopes are on the LTO console One should obtain a relatively large number 7 or more of flatfield images for post processing within IRAF where floating point arithmetic and sigma clipping or median combining are possible the latter to eliminate noise artifacts which may appear in a single observation Since the illumination level differs markedly at J H K and PAH one should anticipate taking data at several
61. lled upsqiid tar at the SQIID web site http www noao edu kpno sqiid http www noao edu kpno sqiid upsqiid tar Restore the package using tar upsqiid tar within your IRAF login directory and follow the README directions for installing the package within your system Since the package consists entirely of IRAF cl procedures no recompiling is needed Assuming you copy the package somewhere in a directory called upsqiid you would put the following definitions in your loginuser cl file task upsqiid your _pathname upsqiid upsqiid cl You also need to edit the file upsqiid cl in the upsqiid package to point to your path instead of my path set upsqdir your pathname upsgiid One loads the upsqiid package by typing upsqiid in the IRAF xgterm window where the cl is running At KPNO the DATA REDUCTION window would qualify Alternatively you can bring up a new xgterm from the menu At the KPNO 2 1m one has the option of performing data analysis on lapis either directly or remotely on royal or azure since the datal and data2 disks are accessible from all three machines Since royal is busy with data aquisition lapis or azure are preferred When running locally on lapis one also needs to bring up a local ximtool window from the menu If the upsqiid package is unavailable type the following in your lapis azure IRAF window task upsqiid data2 ir2meter merrill upsqiid upsgqiid cl upsqiid Appen
62. lly shifts towards smaller values as the night progresses Pick a temperature such as the secondary or the front surface of the primary and monitor that temperature to adjust focus It appears that best focus was a tolerance of at least 0 01 focus units It is useful to note that there appears to be no backlash in the IR secondary At the 4m telescope nominal focus is 7300 with an as yet undetermined temperature dependence FWHM pixels FWHM pixels Data 1 3 5 25 TE Mr OVE MV Dev ir Er 10S ODS AR EV ADR NT ee MS ee er 5 08 5 1 5 12 5 14 5 16 5 18 5 2 5 22 5 24 Focus at 2 1m Fig 9 Focus at the 2 1m telescope Performance Checks SQIID will be installed and checked out at the start of each observing run by a competent and cheerful support scientist Users may confirm continued proper operation during their run with software interrogation and by comparing dark and flatfield frames against standard frames Detector status and temperature information is displayed with the word status s it is also automatically updated at the beginning of an observation Standard values for the default SQIID configuration are displayed above The cryogen temperature readouts are displayed as temperature based on a generic relationship between voltage at constant current and temperature The heater power may vary somewhat around the typical value given However a significant and persistent departure from this va
63. low 8 10000 adu in H and K then by all means use what s been working Adjust the coadds to get a frame time near 150 sec and the total number of frames to get a total integration time of 2200 to 2400 seconds Under normal circumstances these data can be used to generate a sky and a flat so that only a set of darks with the same integration time as the data need to be taken If other flatfield data are available it should also provided to the ToO team as backup Appendix XI FYI ALADDIN Array Architecture The ALADDIN readout protocol is illustrated in Fig 13 The array has 4 physically contingent and electrically independent quadrants that are read out simultaneously column by column by column along a row starting from the outermost edge and ending at the array center Given the reset read wait for integration time read technique employed it follows that the accumulated charge grows from the outer most corner to the center of the array A SQIID channel illuminates a single quadrant Fig 13 ALADDIN Readout Protocol The arrows are indicative of the address architecture within each quadrant pixel addressing moves along rows and columns towards the center of the device merrill noao edu 2007 March 14
64. lue may indicate the dewar is losing its vacuum going soft or that the Closed Cycle Cooler System is losing efficiency If this is suspected contact the instrument support scientist Finally sky or dark subtracted frames may occasionally show a dark or light circular artifact about 30 pixels wide This Phobos effect see Fig 10 results from a region of lower signal in one of the frames and can appear as a positive or negative image anywhere on the array This occurs very infrequently and is apparently a crystal relaxation phenomenon in response to the array being warmed after having been too cold below 25K This can happen over a span of a few hours when the SQIID electronics have just been powered on after they have been off for an extended period The array heater power is controlled by the same power supply as the electronics Fig 10 Phobos effect dark circular patch at lower right 8 Calibration Responsivity Calibration Atmospheric extinction must be calibrated by observations of either a standard star as close as possible to the same zenith distance used for the object or a series of stars that span the range in zenith distance for the observation Typical extinction for SQIID is summarized in Table 9 Table 9 Estimated SQIID Extinction in mag airmass J H K PAH 0 15 0 06 0 08 TBD Flatfield exposures are necessary to calibrate the pixel to pixel gain variations in the array and the effects of the illu
65. ment voltage detector status commands in the Instrument Control window will output here The existence of this window is a diagnostic of WILDFIRE as a system crash will often close it 4 Display This is an XIMTOOL window which may be accessed either through the Instrument Control window where images may be automatically displayed as they are taken or through the IRAF XTERM window via the IRAF display task Those who are desperately attached to the SAOimage display may use it in place of XIMTOOL by killing the XIMTOOL process in the Console window enter ps ax in the Console window to get a listing of the process numbers then kill 9 process and then entering saoimage amp to bring up the SAOimage window e 5 Console This is generally used only for diagnostic or emergency purposes such as killing a hung process or the entire WILDFIRE when it hangs up Bringing up WILDFIRE There are three basic steps in the complete startup of WILDFIRE hardware initialization starting WILDFIRE instrument initialization The procedure below will go through all three steps as would be necessary on the first night the instrument is on the telescope Hardware Initialization This procedure establishes the link between the DSP box and the computer by rebooting the observer s SUN workstation with the SQUID power off The obsinit procedure for the first night of an SQIID block described above includes these steps HISTORIC NOTE The start
66. mination of the array by the internal optics The system response is stable and is very flat across the arrays with a slight intrinsic column to column modulation of a few percent owing to relative array orientations columns may have either NS or EW orientations in the saved and displayed images Consequently the flatfield for each channel should be stable at the percent level under normal illumination and global flatfields can be constructed which are viable for extended periods of time Since direct illumination of the array is possible remember that the secondary mirror is undersized observations near bright sources such as the moon which have atypical illumination should not be use to determine global flatfields Observations during twilight will also have illumination atypical of nighttime observations Because sky flats provide the same array illumination as real observations they are preferable in principle to dome flats using the White Spot It is nonetheless a good idea to obtain dome flats as a backup If one is observing in a sufficiently sparse star field one may use the same set of observations for the object sky and flatfield Because the sky flats will include the array dark current it is necessary to obtain separate dark observations for subtraction from the sky observations Unfortunately what constitutes a dark frame for creating flats is ill determined due to the memory effect which accumulates in time For examp
67. n and Results by A M Fowler Ian Gatley P McIntyre F J Vrba amp A Hoffman 1996 in Proc SPIE 2816 pp 150 160 2 Instrument Description Optical Description The SQUID optical system which is matched to f 15 has a demagnification of 4 The pupil masks are fixed i e not selectable but a reasonable compromise for the 2 1 m and the 4 m telescopes has been implemented n b by design the KPNO IR secondaries handle the central obscuration without requiring a separate cold stop within the pupil mask According to Charles Harmer who has the current design available the worst case blur circle for SQHD is about 75 microns with 90 encircled energy The optical layout of SQIID is shown in Fig 1 The f 15 telescope focal plane is located inside the entrance window near the top of the instrument A series of dichroics and flat mirrors separates the incoming beam into four separate wavelength channels each with its own camera Lyot stop filter optics and focal plane array Dichroic 1 passes L and reflects JHK Dichroic 2 passes H and reflects JK Dichroic 3 passes J and reflects K The telescope exit pupil is imaged at the Lyot stops that are sized to the exit pupil image diameter to serve as an optical cold stop Standard astronomical passband filters located at the Lyot stops restrict the range in wavelength passed to the array The system of dichroics is matched to natural atmospheric windows adequately spaced in wav
68. n source observations to provide sky frames subtracting sky frames on a pixel by pixel basis reduces the contrast problem and allows one to successfully co add data taken over a long interval of time When the targets are much smaller than the array one can accomplish this sky subtraction by moving the target around the array and in effect taking the sky and source data at the same time GHOSTING Each channel has its ghost whose position is opposite the optic axis from its parent bright star Only saturated stars are bright enough to clearly show their ghost which is out of focus covering about 25 of the chip The out of focus ghosts that lie opposite the optic axis from the primary have the following characteristics J H K 90 108 56 pixels diameter 5 5 6 3 5 5 difference in integrated flux in magnitudes In addition the J channel has an in focus ghost located 36 5 pixels east of its parent and 5 4 magnitudes fainter Linearity When a pixel is reset the voltage difference bias between the pixel and detector substrate creates a depletion region that acts as a potential well for the collection of mostly photo generated carriers Electrically one may consider this potential well as a capacitor As charge accumulates in the pixel the depletion region fills in increasing its capacitance and that of the entire pixel node Changes the gain of the system resulting in a sub linear voltage charge relationship which quickly rolls off satu
69. n the computer room downstairs use the L1 A or Stop A keys then enter boot After system has returned login as telescope on the instrument computer with the current password e In the control room go to the Instrument Control window and continue with the RESTART procedure below RESTART AFTER INSTRUMENT POWER INTERRUPTION If the power to the instrument was interrupted but the black Heurikon DSP box in the computer room remained powered up and the computer was not rebooted e In the Instrument Control window enter startwf following the interactive startup procedure turning the instrument power ON when requested using the switch on the instrument e Enter setup sqiid answering y to question about detector activation Note you may use your previously saved via psave parameter filename in place of sqiid e Enter puse parameter file to restore the parameter file active before the crash e Verify pixel dir header dir and nextpic with plist or ped to make sure data will still be going to the desired location and will not overwrite existing data e Verify settime e Reload any scripts with the source command e Continue observing RESTART AFTER HEURIKON DSP BOX POWER INTERRUPTION If the black Heurikon DSP box in the computer room has been powered down then it is necessary to do the following NOTE The order of these steps is important If the dsp box is powered down rebooting the instrument computer is nece
70. nication link to the LTO movie may be used to fine tune position before beginning an observation e 2 1 m The dome lower shutter must be raised to reach large airmasses zenith distance lt 62deg This takes about five minutes Zenith distances lt 30deg are inaccessible with the lower shutter up e The catwalk is off limits to observers unless accompanied by the LTO Check the weather from the ground floor level Control Room Shutdown e LTO will position and close up telescope and dome e 2 1 m Leave chopping secondary rack powered up except last night of block run e Save image data to tape either by o wfits IRAF FITS images to Exabyte or DAT o tar FITS images to Exabyte or DAT o wfits IRAF images to FITS files on disk and tar them to tape o ftp files to home computer e Enter work requests into service program through the LTO e Verify operational hours for LTO to enter into electronic observing log Observing Platform Cassegrain Cage Shutdown e Leave the Instrument power supply alone normally on e Close the lower SQHD guider dark slide The stick shift on the west of the SQHD telescope interface should be fully in e Set the internal SQIID aperture wheel to dark Status is indicated by the lights at the hank crank on the North side of SQUD Turn on the indicator lights and follow the directions posted Turn off the indicator lights when you are finished Computer Room Shutdown e Rewind and remove tape e Leave
71. nnels of SQIID are contained in Supplement 1 Channel Specific Characteristics These masks include the combined effects of intrinsically bad pixels and instrumental vignetting 9 Appendices Appendix I Telescope Checklist Computer Room Setup Computer Heurikon DSP power on normally left on Observing Platform Cassegrain Cage Setup The telescope and dome are operated by the Telescope Operator nights or the Technical Assistant days Arrange schedules with them in advance for positioning for dome flats and opening the telescope and dome at the start of the night The observer should e Verify that the Instrument power supply is on normally on Switch is on the right South side near the top by the power cord of the electronics box mounted on SQIID If the sides of the rocker show red the switch is on e Check that the upper SQUD guider dark slide fiberglass slide with aluminum pull tab at top of telescope interface guider on the South is out This is normally removed at the start of a run but it may have been reinserted for added protection in response to high humidity rain e Check that the lower SQIID guider dark slide is out The stick shift on the west of the SQID guider should be fully out Pull it out firmly to engage the detent e Check that the internal SQIID aperture wheel is open except when actually obtaining darks Status is indicated by the lights at the hank crank on the North side of SQUD Turn
72. now activated The housekeeping window and the saver task should successfully start If you want to use a different parameter file than the default sqiid parameter file that was executed by the startup script you can enter puse parameter filename at this time SQUID is now ready for operation Checking system noise One tests the system noise by taking 10 dark exposures with short 1 sec integration time These data are combined with the IRAF imcombine task to determine the rms per pixel The IRAF phist task can be used to examine the results nbins 200 z1 0 z2 25 A typical result is shown in Figure 12 Peak values significantly higher than the 3 5 4 0 shown are indicative of excess noise Either the array temperatures have not yet stabilized detector heater power is not on unless the instrument power is on or there is a problem with the electrical ground SQHD should not be run with instrument power connected through an isolation transformer hm Se ee ee nn r a dS EE EY Van a A dle 19 20 Fig 12 Typical detector noise for SQIID The K channel has the long tail Appendix X ToO Observations Target of Opportunity Observations The typical Target of Opportunity ToO observation for SQIID entails deep observations of a transient target such as a Gamma Ray Burst A special script has been that moves the telescope a pseudo random distance between exposures Hopefully the tcl code has been copied to the wfire subdirect
73. nt on the screen one at time those parameters selected by eask and the current value prompting for entry of a new value or cr which will enter the current value The command go will begin an observation but will use the current values for the parameters except the picture index which will be automatically incremented The command movie will begin a loop consisting of an observation using the current parameters and a display this may be terminated with end at any time The observation in progress will be completed and displayed Movie observations are stored on disk This is unfortunately necessary to prevent orphaned pixel files from filling up the disk A recommended procedure is to include the filename parameter in the ask menu and change to a dummy filename at the beginning of a movie When returning to data taking one may reset the filename to that used for the data If one wishes to retain continuity in the index number it is also necessary to reset nextpic to the value before the movie observations Keep good logs The ask command will cycle through the selected parameters prompting for changes just as with obs but will NOT begin an observation This command is useful for checking parameters and is essential before executing movie which will use the parameters for the previous observation even if it were 600s in length The combination of ask and go is a perhaps preferable alternative to observe One may abort an observa
74. o you want to save in IRAF format n default is FITS cr At this point the transputer nodes will bootstrap and tld files will load Eventually when the startup script automatically executes setup phoenix you will see messages regarding the downloading of the microcode setting assorted voltages When this is completed the final message will appear Do you want to activate the array y or n n You will see messages about assorted voltage failures and servo errors since the PHOENIX task looks for DACs and for motors that SQIID does not have but the housekeeping window and the saver task should successfully start a T Go to the Instrument Control Window and exercise the system by typing status s status v and status t then exit the system by typing exit Continue by typing g sqiid Answer the questions Do you want windows y cr Do you want to save in IRAF format n default is FITS cr At this point the transputer nodes will bootstrap and four tld files will load Eventually when the startup script automatically executes setup sqiid you will see messages regarding the downloading of the microcode setting of 4 values of VddCI1 1 3 VddCl2 3 5 VggC11 4 9 VggC12 2 8 and Vset 1 8 When this is completed the final message will appear Do you want to activate the array y or n y You will see messages reporting 4 biases being set followed by e The arrays are
75. ollowing discussion observed output values have not been corrected for the unseen charge collected during delay between biasing the detectors reset and the first non destructive read of the bias A second non destructive read is taken an integration time later Only the difference between reads is output In detail the global reset mode used to operate SQIID resets all the pixels at the same time and then performs a non destructive read of the array The first pixel is read out shortly after the global reset and the last pixel is read out 0 61 sec after the global reset The charge accumulated at the time of the position dependent first read is lost since its value does not get reflected in the difference Hence the reported signal is always less than the total signal on the array at the time of the second read At short integration times and high rates of photon arrival bright stars and or high background this unreported charge can lead to a significant underestimate of the signal outside the scope of the usual linearity correction The unseen charge can be accurately estimated apart from noise issues on the basis of the timing but since the amount of unseen charge is position dependent one is better off not going there Ideally the data fit are always within the regime where this correction for unseen charge was small This is not the case for example when doing 0 84 sec integrations on standards One normally expresses the departur
76. on and will not overwrite existing data e Verify settime e Reload any scripts with the source command e Continue observing WILDFIRE PROCESSES By way of information these are the WILDFIRE specific processes running on royal at the 2 1 m under normal operations 230 pl IW 0 00 bin csh usr wfire bin startwf lapis 242 pl IW 0 00 bin sh usr wfire bin startwf 290 pl R 7 25 usr wfire bin SQIID control 249 p2 IWN 0 00 bin csh usr iraf extern ice startup config fire start red 304 p3 IW 0 00 bin csh usr wfire bin sun daemons SQIID fits 311 p3 R 26 08 saver fits 312 p3 S 0 07 hkserv config SQIID DISPLAY lapis 0 0 EXINIT set optim e e e Appendix IV Data Reduction Guide INTRODUCTION Given the large variety of observing programs being carried out SQUID no single approach to data reduction is universally applicable This section reviews the promising approaches to data reduction for several specific observing scenarios observations of a bright stellar source a faint stellar source and an extended object IR imagery with the InSb array presents several problems not encountered in visual imagery with an optical CCD These include high background with strong variable emission lines and regions of bad pixels Fortunately the frontside illuminated InSb arrays to not suffer from fringing so that theTo overcome the bad pixels we recommend taking a large number gt 5 of observations of a given object spatially offset b
77. on appears to be radially symmetric and is well represented by the addition of a cubic term This simplifies the data reduction enormously as spatial registration at any channel can be directly translated into registration at all channels Since the individual channels of SQUID illumine a single quadrant of a four quadrant array which is has to be physically mounted within a small volume so as to not interfere with its neighbors and the best quadrant of each device is selected the relative orientation on the sky on the array is channel specific From the point of view of the array which is read from the outside corner see Fig 13 rows are oriented along the horizontal and columns along the vertical the sky is natively seen oriented as follows Initially SQIID data where displayed and saved oriented as shown As of September 2000 the saver task correctly handles the orientation issue during the saver process Images saved to disk and automatically displayed are properly oriented with North up and East to the left Mechanical Description Located at the telescope focal plane are the imager cryostat the mechanical interface and the associated warm electronics in two boxes mounted to the instrument Fig 2 shows a side view of the instrument and identifies the important parts SQIID communicates with a remotely located instrument computer and ultimately with the user in a remote observing room Fig 3 Even though the f 15 focal plane at t
78. ork The pixel scale and the unvignetted spatial coverage at the two telescopes are summarized in Table 1 Table 1 Pixel Scale and FOV Telescope f ratio arcsec pixel pixels RA X DEC field arcsec 2 1 m 15 0 69 440 X 460 304 X 317 4 m 15 0 39 440 X 460 172 X 179 Filters Each channel of SQHD has its own fixed filter We are unable to accommodate other filters tailored to specific programs The deployed filter complement as of February 2002 is summarized in Table 2 Note Prior to February 2002 the K channel contained a Barr K filter Table 2 SQUD Filters vendor midpoint FWHM bandpass HP short HP long Channel z z ID microns microns microns microns J Barr J 1 267 0 271 1 131 1 402 H Barr H 1 672 0 274 1 535 1 809 K pre 02 2002 Barr K 2 224 0 394 2 027 2 421 K post 02 2002 OCLI Ks 2 225 0 35 1 95 2 30 Barr L PAH 3 299 0 074 3 262 3 336 J filter data are estimated from the manufacturer s warm tracing by applying 1 63 shortward shift Other data are from manufacturer s 77K tracings Dichroic transparency has not been applied The geometric distortion is comfortably small within the unvignetted area so that the data from the different channels can be brought to a common basis using a superposition of linear transforms position shift rotation and magnification and a modest amount of pincushion barrel distortion Note J has pincushion distortion and HK have nearly identical barrel distortion The geometric distorti
79. ory located within data2 2meter wfire at the 2 1 meter and within datal 4meter wfire at the 4 meter for easy access Since these scripts are not part of the static WILDFIRE dictionary they must be sourced from within the Instrument Control window by sourcing a file called setup_grb source data2 2meter wfire setup grb tcl This file executes the following commands source data2 2meter wfire randith2d tcl source data2 2meter wfire jrand tcl source data2 2meter wfire getdelay tcl source data2 2meter wfire randseed tcl set iseed 17427 setIntegration 15 0 0 11 10 15 10 40 190 seconds pics 1 tcp_on Command useage is randith2 N pictures min_offset_x min offset y max_offset_x max offset y A typical choice would be randith2 15 4 4 10 10 This would generate 15 images and take 2250 seconds total integration time and probably burn about 50 minutes of wall clock If the special scripts noted above are unavailable one should do the following Use set time to set JHK integration time to 15 sec and coadds to 10 e Run one of pattern scripts such as o do spiral with a separation of 8 to 10 arcsec Run this twice o do standard on with a separation of 8 to 10 arcsec Run this thrice o do field on with a separation of 8 to 10 arcsec and a 4 by 4 grid The integration time of 15 sec is conservative intended to keep things on scale If your own observations suggest that a longer time such as 20 to 25 seconds keeps counts be
80. otstrappping node 100 are due to poor fiber communications or failed memory in the SQIID electronics Overheating or lack of power are the most common cause of such failures Bootstrapping the remainder of the network Bootstrapping node 100 Bootstrapping node 101 Bootstrapping node 102 Bootstrapping node 103 Bootstrapping node 203 Bootstrapping node 202 Bootstrapping node 201 Bootstrapping node 200 Bootstrapping node 2 Bootstrapping node 10 Network successfully bootstrapped Downloading program tld SQIID b011 tld Downloading program tld SQIID inst tld Downloading program tld SQIID seq tld Downloading program tld SQIID dspw tld Program downloading completed WILDFIRE SQIID SYSTEM CONTROL LAST BUILT Fri May 21 14 47 16 MST 1999 entering wfinit 1 28110 2 28111 NOTE All parameters should be given in j h k 1 order j hand k integration time lnr s amp coadds must be identical Be sure to set itvoffset before using sqtv or sqiid Get_picture message received from Saver number digital averages for j hk 1 set to 4441 Be sure to rerun settime to correct the sequence timing Min time for j 0 61 Min time for h 0 61 Min time for k 0 61 Min time for 1 0 061 L Integration Time 0 321 L coadds 1 JHK Integration Time 0 321 JHK coadds 1 Initialization Complete Note at this point WILDFIRE accesses and loads the sqiid parameter file If the system stops here gt Enter setup sqii
81. out a telescope operator The filters are fixed in place and dark slide and window covers are the only moving parts SQIID employs closed cycle refrigeration instead of liquid cryogens and in its prior configuration operated flawlessly for periods as long as 40 days providing an unparalleled degree of system stability Typical observing programs include e taking a few 2 5 exposures on the same target with small offsets to counter ghosts and bad pixels and improve spatial sampling of the images e taking many exposures of the same target with a dither pattern of offsets to build up long exposures e spatial mosaics of dithered pairs of images covering larger regions with limited overlap between images to build up large images Each detector is a Raytheon Vision Systems nee SBRC ALADDIN 1024X1024 indium antimonide InSb hybrid focal plane array with 27 micron pixels 90 geometric and 100 optical fill factors produced under contract to the ALADDIN Consortium The ALADDIN Consortium consisting of NOAO KPNO and the US Naval Observatory Flagstaff under the engineering guidance of Al Fowler has designed developed characterized and optimized the performance of the ALADDIN array for the wider community Since each SQUD channel illuminates a single 512X512 quadrant devices need only one otherwise excellent operable quadrant to be acceptable The optics for each channel are independently optimized with a relatively narrow bandpass apart
82. parameter set s as needed for observing with ped and eask and save with psave Create and source any custom observing scripts required e Check that status s gives proper values SQUID is now ready to take data Calibration Data Although sky flats are generally adequate for reducing SQIID observations dome flats may be useful Dome flatfields may be done either in the afternoon before observing or in the morning Remember that you will need dark frames taken the same way integration time and number of coadds as your sky dome exposures to properly produce your sky flats Since the temperature and operating conditions for SQIID are highly stable by design one should not have to repeat flatfields once they have been verified In any case it may be desirable to take some short and long 30s dark frames before the first night of observing to verify performance e Telescope focus set to nominal value for SQIID approximately 5 20 at 2 1 m 7300 at 4 m Dome flats o Dome and telescope positioned by TA LTO to center of flatfield target o Dome lights off door to visitor gallery closed o Turn on flatfield lamps intensity controlled by buttons at LTO console While all channels are exposed simultaneously one may find different lamp settings are required to be properly onscale at each channel Flatfield series should be obtained for each bandpass J H K used for observing as each wavelength channel is serviced by its own array Two s
83. performs a number of functions relevant to this operating procedure e Switching from ICE to WILDFIRE environment on the first night of an IR observing run e Efficiently and gracefully cleaning the disk of data from previous observers e Storing the current observer name and proposal number for archiving First Night of SQUD Block On the first night of an IR block the ICE environment will still be active the presence of the CCD Acquisition and CCD Reduction windows will verify this It will be necessary to run obsinit to change to the WILDFIRE environment since the hardware may be in an unknown state it isalso recommended to run through a complete hardware initialization on the first night of an IR block as part of the obsinit process This will involve rebooting the observer s SUN workstation with the DSP in the computer room powered on and the SQUID instrument power off The SQUID instrument power supply is located on the instrument itself The rocker switch is on the right South side near the top by the power cord of the electronics box mounted on SQIID e Verify that the DSP power is ON Black Huericon box in computer room e Verify that the power to SQIID is OFF power supply on SQIID itself e Quit the CCD Acquisition CCD Reduction and Ximtool SAOimage windows e Logout of any other IRAF processes e Enter the command obsinit ina Shelltool or Xgterm window One will be led through an interactive process o nam
84. rates when the pixel voltage reaches that of the detector substrate zero bias Technically a pixel will continue to accumulate charge even into forward bias but its response by that time will be significantly nonlinear As a direct consequence pixel response departs from linearity in a predictable fashion for accumulated signals above a device specific level Since the total capacitance which determines system gain is the sum of the distributed non varying capacitance of the system and the variable capacitance at each detector node the degree of non linearity is a function of the ratio of nodal to total capacitance Since key pixel parameters such as quantum efficiency are very uniform the linearity appears to be a global property of the array rather than pixel specific Increasing the bias on a pixel will not only increase the depth of the potential well but by decreasing the capacitance of the depletion region in relation to parallel components of the node capacitance will result in a more linear voltage charge relation As a result a bias increase from 0 6 to 0 8 volts will effectively double the charge capacity of the pixel This comes however at a significant cost in dark current which increases dramatically with bias Therefore we recommend a bias of 0 6v for JH 0 7 for K and 0 9v for high background L band observations where the increased dark current is not important These are the default bias values for SQUID In the f
85. rder I sec the observing efficiency declines to 50 and for integration times of order 10 seconds the JHK observing efficiency approaches 90 It is equally important to understand the relationship between JHK integration time and L integration time that affects L observing efficiency During the course of an integration SQUID simultaneously resets the JHK arrays then simultaneously performs a non destructive read equivalent to a CCD bias frame on the JHK arrays waits roughly an integration time then reads out the JHK arrays again Between JHK reads the L band array is read out in pairs and differenced as often as will fit between the JHK read pair and the results co added Since there is some dead time before running L and since the minimum integration time is roughly the readout time the maximum time spent integrating at L within a JHKL cycle is less than half the JHK integration time One could use a different technique to read L e g row reset to improve efficiency but we have yet to produce the complex code required to read L differently than JHK and will most likely produce a code employing row reset for all channels The situation is summarized in Table 9 for the case of the shortest L time Table 9 L channel observing efficiency JHK L total L L time per time tme time coadd sec sec coadds sec L JHK 0 11 1 00 1 0 11 11 0 0 11 2 00 6 0 66 33 0 0 11 3 00 10 1 10 36 6 0 11 5 00 19 2 09 41 8 0 11 10 00 42 4 62 46 2
86. reen LED in the DCU should be on and the two red LEDs off If either or both red LEDs is lit there is a fiber problem which must be repaired A similar set of LEDs in the DSP box can diagnose fiber problems at that end Bad fiber optic connection see above Even if red LEDs are off one or more fibers may have poor throughput which must be measured Power supplies may be connected improperly Check that the analog connector goes to CCD Power and not PS 10 Power on the telescope Bad fiber optic connection see above C004 may not be configured and a full startup may be necessary DSP cycle reboot startwf System stuck in funny state Full startup may be required If that does not help check for proper power connection and fiber throughput Link to TCP computer is down This is usually solved by rebooting the TCP computer WILDFIRE will still work but cannot move telescope or retrieve telescope status information for header In addition comments suggestions and descriptions of persistent problems should be emailed to wfire lemming which has been set up as an equivalent to service for WILDFIRE instrumentation Parameter Sets parameter sets are used to control the attributes of data acquisition A listing of the parameters is given below Because the data are saved directly as IRAF images note that parameters include not only observation specific items such as integration time but archiving items such as the IRAF filename
87. ric background ultimately limit the cohesiveness of a data set multi color observations are necessarily limited in depth and or areal extent by the mechanics of taking the observations and the systematic effects of combining them into a single coherent data set The advantage of SQIID is self evident During the time necessary to take the observations at the most time consuming wavelength one in effect gets the other channels for free under the same observing conditions Systematic effects are limited and determinate This is why SQIID competes favorably with larger format arrays for multi color applications In addition wide field L band imaging is possible albeit with restricted bandpass with sufficient sensitivity to detect and accurately locate red sources in the field This feature is particularly important for detecting and identifying for further study sources with IR excess highly reddened sources and intrinsically cold sources near the galactic plane where the star formation process is still active Details of the prior SQIID system are discussed by Ellis et al 1992 The Simultaneous Quad color Infrared Imaging Device SQIID A Leap Forward in Infrared Cameras for Astronomy by T Ellis R Drake A M Fowler I Gatley J Heim R Luce K M Merrill R Probst amp N Buchholz 1992 in Proc SPIE 1765 pp 94 106 and the ALADDIN detectors are discussed by Fowler et al 1996 ALADDIN The 1024x1024 InSb Array Design Descriptio
88. sion gain is approximately 11 electrons per ADU Prior to 2005 the JH bias was 600mv As of January 2005 the JHK bias is 700mv Saturation Eventually a pixel will accumulate sufficient charge to forward bias it to the point where no more is collected resulting in a condition known as saturation The reset read read address cycle used in double correlated sampling Fig 4 results in a characteristic but unusual saturation behavior For a given integration time the effect of increased flux is a steeper slope of the voltage time curve As the flux increases the voltage V will eventually saturate while the voltage V will continue to increase because of the time interval between the reset and the first read the difference signal will thus decrease with increasing flux Finally the detector will saturate in the short interval between the reset and first read resulting in identical values for V and V or a difference value of zero Thus the double correlated signal relation with flux is initially nearly linear then increasingly nonlinear and eventually decreasing to an ultimate value of zero as one saturates The A D channels 2 for J H K and 8 for L will saturate at slightly different levels resulting in an evident odd even column pattern These effects are evident in a Saturation Image of the L band in which the flux increases rapidly from the bottom to the top of the array Pixel Masks Representative pixel masks for the J H K cha
89. sk params integration sec la List Ask params filename la List Ask params header dir la List Ask params pixel dir la 1 List Ask params mode 1 List Ask params pic num la List Ask params ucode 1 List Ask params display 1 List Ask params ra 1 List Ask params dec 1 List Ask params epoch 1 List Ask params offset 1 List Ask params type 1 List Ask params airmass 1 List Ask params comment 1 List Ask params im_list 1 List Ask params varl 1 List Ask params var2 1 List Ask params var3 1 List Ask params var4 1 List Ask params save 1 List Ask params archive 1 Changes to ask and the parameter file are preserved using gt Enter psave my set lt psave WARNING Overwriting existing file wfpar SQIID sqiid par OK to proceed y or n y Saving to wfpar SQIID sqiid par Setting detector bias The following interchange sets the bias on the K channel gt Enter setbias 2 0 7 lt setbias 2 0 7 Array 2 Detector Bias 0 set to 0 681 The sequence noted below sets all the biases gt Enter setbias j Enter setbias h Enter setbias k 7 Enter setbias 1 9 lt Appendix IX Installation Issues Initializing the Environment with OBSINIT The optical CCD ICE and infrared WILDFIRE environments are both operated from the same account on the 2 1 m 2meter and 4 m 4meter telescopes The all important obsinit command
90. ssary Make sure no one else is using the instrument computer at the time If only the power to the instrument has been interrupted perform the procedure above Whenever the instrument computer is rebooted the instrument power must be off and the heurikon dsp power on e Verify that the Heurikon DSP box is powered up Turn OFF power to the instrument using the switch on the instrument Turn the DSP power OFF for 30 sec then ON e Reboot the instrument computer o At the 2 1m on the royal console in the computer room downstairs use the L1 A or Stop A keys then enter boot After system has returned login as telescope on the instrument computer with the current password o At the 4 m on the khaki console in the computer room downstairs use the L1 A or Stop A keys then enter boot After system has returned login as telescope on the instrument computer with the current password Go to the Instrument Control window and enter startwf Follow the interactive procedure Turn ON the instrument power when requested by startwf e In the Instrument Control window enter setup sqiid answering y to question about detector activation Note you may use your previously saved via psave parameter filename in place of sqiid e Enter puse parameter file to restore the parameter file active before the crash e Verify pixel dir header dir and nextpic with plist or ped to make sure data will still be going to the desired locati
91. structive Readout Pixel Readout Photo electrons accumulate until reset Difference between two reads minimizes fixed pattern noise a kTC noise 0 5V N CDS Signal ov Readout oD 8 5 gt wn oO S ge ke a Double Correlated Sampling Fowler 1 Readout ov Time Fig 4 Schematic representation of the voltage on a single pixel as a function of time The intervals labeled reset and readout suggest the time when these events occur and are not to scale The operating microcode for ALADDIN arrays includes a provision for multiple correlated sampling frequently referred to as Fowler sampling in deference to its discovery Al Fowler of NOAO in which the reads consist of a series of N nondestructive reads coadded to yield the values V and V This greatly reduces by approximately N 5 the array read noise on long low background integrations Since SQIID observations are generally background limited specifically they are not detector limited we only use Fowler 1 which corresponds to double correlated sampling At the shortest integrations within the SQIID environment selecting coadds gt 2 also improves S N by approximately N Table 3 summarizes the device characteristics and measured performance levels according to standard lab protocol of the ALADDIN arrays assigned to SQIID SQUID was designed for background limited performance at low to moderate backgrounds The ALADDIN array has 27 X 2
92. t parameter set listing each parameter in turn and prompting for new entry cr returns the present value At the beginning of a run one should execute ped and set up those parameters falling into categories 2 and 3 above NOTE One cannot specify a non existent header or pixel directory in ped it is necessary to go to the IRAF XTERM window and create those directories first Since it is cumbersome to go through the entire parameter list for each observation there is a command eask which runs through the entire parameter list permitting the observer to specify which parameters should be queried at the beginning of each observation Entering la for a parameter selects it for the observation menu entering 1 excludes it NOTE The up arrow key may be used to back up through the ped list if one wishes to change a previously entered parameter When this is complete save the parameter set with the command psave filename This will save both the edited parameter set and the menu selected by eask in the file filename par Should the system crash this information may be retrieved by the command puse filename Should major changes be made to the parameter file such as change of header or pixel directory say on another night of the run it is a good idea to psave the updated file so it and not the previous version will be recovered by puse Observing Words The basic observation is initiated by the command observe The system will pri
93. t_offset turn tcp header information on tcp_on run through standard 5 position grid one observation picture taken at each position The sequence starts centered but takes no data and ends with data at center set step l east 30 0 south 30 0 set step 2 north 60 0 set step 3 west 60 0 set step 4 south 60 0 set step 5 east 30 0 north 30 0 run through ask sequence ask allow for graceful exit if yorn Do you want to continue then error Safe exit issue exit procedure reminder puts stdout Hit return to abort Grid set il while i lt 5 eval S step i go if select then error error in sequence Hk Pet incr i issue beep at end puts stdout Sequence completed beep 10 Appendix VI Cautions and Caveats A number of operational issues are worthy of note WARNING Do not let the designated data disk fill up You will lose data When the data acquistion disk is full zero length images are written to disk and the data are lost Although the housing window dutifully reports the available space after each exposure there is currently no additional visual or audible alert that the disk has filled Although the storage preferred location for data acquisition data2 is large 4 GB each exposure quad of 512X512 floating point images is 4MB To avoid filling the disk it is recommended that you move the images from previous nights over to a larger disk such as datal b
94. te a sky frame from a median of the individual observations Subtracting this median sky from the individual observations removes the dark and first order sky Each image is then divided by the flat SQUD Package SQUD produces simultaneous images of the same field in the J H K and narrowbnd L passbands using individual 512X512 quadrants of ALADDIN InSb arrays The observations are generally background photon statistics limited Typical observing programs include e taking a few 2 5 exposures on the same target with small offsets to counter ghosts and bad pixels and improve spatial sampling of the images e taking many exposures of the same target with a dither pattern of offsets to build up long exposures e spatial mosaics of dithered pairs of images covering larger regions with limited overlap between images to build up large images These three kinds of observations are distinguished because they require somewhat different data reduction strategies This document describes a set of IRAF programs created by Michael Merrill at NOAO designed to facilitate the reduction of SQUID datasets These programs reside in the IRAF package upsqiid They have a number of imperfections in the user interface especially a large number of irrelevant parameters and currently do not have help files NB The SQIID package is not an officially released and supported IRAF package all queries should be directed to Michael Merrill at NOAO merrill no
95. ter file puse filename load the named parameter file ped edit the current parameter file selected by puse asking all questions regardless of query status ask prompt for the eask selected subset of parameters within the current parameter set eask iterate through all the known parameters allowing the user to specify which parameters are queried and which are displayed After each question an 1 signifies display only a signifies query la will list the current value which may be selected by cr or accept a new entry ACCESSING INDIVIDUAL PARAMETERS Note many SQIID parameters have 4 values one per channel which are entered on the same line separated by whitespace The last argument in a series is adopted for the rest of the arguments 1 yields 1111 12 yields 1222 123 yields 1 233 When no argument is given task prompts with current value coadds returns the number of coadds for next image pics n sets the number of pictures to be taken at each observe go set time f f2 n prompts and sets the JHKL coadds and integration time in seconds to millisec level sets JHK time to f sec L time to f2 sec and JHK coadds to n task computes L coadds This is the preferred method to set integration time and or coadds setIntegration f f2 n sets JHK time to f sec L time to f2 sec and JHK coadds to n task computes L coadds nextpic n sets the picture index appended to filename to n header_dir sets path for F
96. ter hub They just need to do vncviewer lapis 1 and enter the 2meter password Since this will slow the VNC linkage viewing from other machines should not be abused with extended usage during observations e Important currently after an obsinit it takes about 2 minutes for the VNC to restart so be patient If it becomes necessary to reboot royal go to the royal console in the computer room and use the L1 A or STOP A keys and then enter boot e Do not try and run a web browser on lapis Although Netscape has been removed from the menu it can still be run it a command line Use sapphire for web browsing and other fun stuff we have tested the printer and it works Lapis should only be used for acquiring images e People can now use the xcdroast icon to burn DVD Rs and CD Rs Bob is gonna send you some instructions Meanwhile here is the documentation and FAQ on the web http www xcdroast org manual e If just the VNC needs to be restarted log on to lapis as user 2meter and do restart vnc and after 2 minutes a new one should be ready Initializing the Environment with OBSINIT The optical CCD ICE and infrared WILDFIRE environments are both operated from the same account on the 2 1 m 2meter and 4 m 4meter telescopes The all important obs init command performs a number of functions relevant to this operating procedure e Switching from ICE to WILDFIRE environment on the first night of an IR observing run e Eff
97. that has slowly evolved to the meet changing needs of computer support Historically SQIID was operated by the user from a SUN workstation in the telescope control room through the WILDFIRE system a transputer based system that communicates over optical fibers WILDFIRE supports fast co adding in place movie mode and data transfer directly to the SUN Since WILDFIRE is tied to Sbus based hardware and a SunOS host system there is little room for growth in the core machine The system was hard pressed by the upgrade from four 256X256 arrays to four 512X512 arrays during the SQIID upgrade Movie mode was dropped owing to I O delays associated with this upgrade The current configuration has SQHD remotely operated from a Linux based Workstation physically located in the control room that connects to the SQUD host Sun Workstation now completely in the computer room through a VNC server The WILDFIRE system uses transputers and transputer links to control and acquire data from SQUID A transputer is a single chip microcomputer with its own local memory and communication links which can operate either by itself or in conjunction with other elements linked to form computing arrays and networks The WILDFIRE system consists of three main hardware components The SQIID instrument control unit inside the DCU Digital Control Unit box contains two transputers that provide housekeeping data and control and generate the sequences that operate each array
98. the instrument computer for any reason There should be no reason to execute obsinit more than once during a run If a reboot is required the login procedure in the window displayed above will automatically bring up the WILDFIRE windows USTARUBENT COMNTAIL DATA REDUCTWNII Fig 5 Windows layout after initiation of WILDFIRE A brief description of the windows follows 1 Instrument Control This is the window for entering all commands controlling the instrument or telescope It will initially have a instrument computer prompt and a prompt when the instrument microcode is running e 2 IRAF XGTERM This window is used for IRAF commands for analysis of data or for shell commands such as creating directories moving or archiving data e 3 Instrument Status Once the instrument microcode has been loaded this window will appear Instrument voltage detector status commands in the Instrument Control window will output here The existence of this window is a diagnostic of WILDFIRE as a system crash will often close it e 4 Display This is an XIMTOOL window which may be accessed either through the Instrument Control window where images may be automatically displayed as they are taken or through the IRAF XTERM window via the IRAF display task Those who are desperately attached to the SAOimage display may use it in place of XIMTOOL by killing the XIMTOOL process in the Console window enter ps ax in the Console window to
99. tion Alternative parameter named parameter files can also be invoked via setup filename ucode dl microcode name startwf exit trouble hung newobserver status IslvItlf longheaders onloff tep on tep off list array microcode currently in use also in image header download specific array microcode WILDFIRE initiate bootstrapping and downloading of the WILDFIRE system deactivate the array and exit the WILDFIRE controller open troubleshooting session do NOT enter in Instrument Control window attempts to complete link protocol used as part of the restart procedure when WILDFIRE is hung INSTRUMENT CONTROL window unresponsive and data collection stalled must be entered in Console window HOUSEKEEPING enter observer name and proposal ID for image header display a status screen general status Isl voltageslvl temperaturesltl filters Ifl will disable enable house keeping data in the header enable link to TCP for telescope status info and offsetting disable link to TCP for telescope status info and offsetting PARAMETER FILES Note a parameter has two attributes its value and flags indicating whether the parameter and its value should be displayed and or queried when the ask or observe tasks are run list the names of the available parameter files plist list all the current parameters psave filename save the current parameter set values and ask display flags to the named parame
100. tion such as an unintentional 600s movie by entering abort in the Instrument Control window the system should respond by acknowledging the abort and the observation should terminate gracefully in a few seconds This can sometimes turn off the display and save operations so it is advisable to re enter save j h k 1 or whichever subset you have been using and display k or whichever channel you have been using after an abort TCL Scripts and IRAF Tasks The user interface is written in the Tool Command Language tcl which is well suited to the construction of scripts for data taking Scripts are a powerful tool for executing a sequence of tcl commands including telescope motions instrument motor commands and observations as a single executable program Even for those who are not veteran programmers most of us simple scripts are fairly easy to construct Scripts are highly recommended for spatial sampling dithering and linearity calibrations The best recipe for starting out is to copy an existing script to a new file and then edit that file as desired The first line of the script file contains the base name of the script file proc and must be edited to reflect the new name of a script created in this manner Before the initial use of a script or after a system restart it must be identified as an executable in the Instrument Control window using the full path name of the file e g source data2 2meter tclSamples scriptname tcl
101. tor Array 0 Detector Bias set to Array 3 Detector Bias 0 set to The arrays are now activated Array 1 Array 2 ooo Parameter files 0 575 0 681 0 571 0 589 WILDFIRE operates through parameter files The default default parameter set is sqiid If you are restarting the system and have saved your own parameter file my_set activate it by typing gt Enter puse my set lt Examine parameter list by typing gt Enter plist lt plist Title Number of coadds Number of lnrs Number of pictures Integration time seconds Filename template Header Directory Pixel Directory Process mode Picture index Microcode Channels to display RA of object DEC of object EPOCH of object Observation offset Image type Current airmass Comment Image name list file Header Var 1 Header Var 2 Header Var 3 Channels to save Channels to archive 1111 1111 1 0 321 0 321 0 321 0 321 a 03d s data2 2meter data2 2meter pixels stare stare stare stare 0000 sqiid4d 2231 01 0 00 00 0 00 00 1950 0 object 1 none tmp list One edits the ask sequence the questions task ask will ask you by gt Enter eask lt In this exchange 1 corresponds to list and la corresponds to list and ask during the ask sequence Representative choices are given below eask List Ask params title 1 la List Ask params coadds 1 List Ask params lnrs 1 List Ask params pics 1 List A
102. traction work well as long as one operates in the linear lt 10000 ADU region of the detector TRIMMING AND LINEARIZATION FLATS DARKS amp SKY FRAMES Proper data reduction requires accurate solutions for the small additive effects of internal illumination and charge generation DARK frames the large additive effects of sky illumination SKY frames and the multiplicative effects of position dependent pixel sensitivity FLATFIELD frames The creation of DARK FLAT and SKY calibration frames are the first step in the data reduction process The DARK frames are simple to obtain and process but the FLAT and SKY frames are more difficult to create and are crucial to the quality of the final images Compared to optical band CCD observations infrared observations are extremely background limited Furthermore the background in the near infrared is variable at many temporal and spatial scales System SKY frames are established from observations with the same integration time and near in time and place to the source frames This is done by interspersing frames of off source ideally blank sky fields in the sequence of source observations Many of these sky frames each at different position are then median filtered to remove celestial sources to generate a SKY frame which is measure of the temporally stable illumination on the array including dark current and fixed pattern noise System FLATFIELD frames are established using the sky as a un
103. ts for grid separation sky dither vector small motion must have two values and sky offset vector large motion also two values all in arcsec The vectors are ordered RA Dec with for E and N for W and S The command line version is do 9rstr gridsep ewdither nsdither ewsky nssky do_9raster_on same as do_9raster but updates telescope information in the image header for each image in the sequence The command line version is do 9rstr on gridsep ewdither nsdither ewsky nssky Refer to the Appendices for listings of WILDFIRE and SQIID commands Appendix II and troubleshooting procedures Appendix II tmove Michael Merrill s provisional IRAF script tmove may be used for centering stars on the array using an image displayed in the ximtool window Because this is not yet a standard IRAF task it will probably have to be manually installed for an observing run idisp If the file tmove cl is not found in the telescope or tclSamples directory download it The script is defaulted for SQUID at the 2 1 m If you are at the 4 m it will be necessary to edit the telescope string parameter in the file tmove cl In the data directory identify the task to IRAF by entering the full path name of the file e g task tmove datal 4meter tmove cl To execute enter tmove You will be prompted to put the cursor on the star in the ximtool display Entering c will compute the offset to the center 256 256 o
104. up script for WILDFIRE was simplified significantly in 1999 The microcode will be loaded automatically and the bias for SQIID set to the default values The dialog during a typical WILDFIRE SQIID initialization is recorded in Appendix IX Starting WILDFIRE HISTORIC NOTE The startup script for WILDFIRE has been simplified significantly in 1999 The microcode will be loaded automatically and the bias for SQHD set to the default values The dialog during a typical WILDFIRE SQIID initialization is recorded in Appendix IX At this point the windows should be present as in Fig 5 Go to the Instrument Control Window and enter startwf This will lead you through an interactive startup procedure READ THE QUESTIONS CAREFULLY simply entering cr will return the default which may not be appropriate For the full startup the replies are e Has the WFire DSP box power been off for any reason since the last time you ran startwf or restart if unsure try n n y e Was the computer rebooted with the instrument power off n y a short initialization process follows e Has the instrument power been off since the last time you ran startwf or restart n y e Is the instrument power on now n you will be prompted to turn on the instrument power cr Which instrument are you using enter PHOENIX IRIM CRSP SQUID etc SQIID the instrument name may now be in either capital or lowercase letters e Do you want windows y cr e Do you
105. us with status s and compare with the nominal values below status s SQIID Base Status Display 18 11 29 H detector K detector J detector L detector Integ time secs 0 855 0 855 0 855 0 185 CoAdds 1 1 1 1x1 Lnrs 1 1 1 1 Number of Pics 1 Detector Temp 29 81K 30 68K 29 81K 30 68K Det Heat Pwr mw 129 39 56 15 146 48 75 68 Observation Settings Mode stare stare stare stare File name test 03d s Index 95 Space Available Header Dir data2 2meter 3046308kb Pixel Dir data2 2meter pixels 3046308kb Housekeeping information is reported via status screens Additional status screens for SQIID are status t SQIID Temperature Display K detector H detector Detector Temp 29 81K Det Heat Pwr mw 136 72 Bench 0 North 40 69K Wheel 46 29K Cold Hd A lst St 32 17K Cold Hd A 2nd St 11 53K status v 30 68K 61 03 Bench 1 South Sieve Plate Cold Hd B 1st St Cold Hd B 2nd St J detector 29 81K 153 81 SQIID PRCD Voltage Status Display K detector H detector 1 0 2 5 2 3 0 1 3 4 2 0 6 3 0 5 0 5 2 790 297 815 589 815 497 992 319 560 886 786 494 186 993 489 983 694 989 991 J detector 1 779 0 257 2 926 5 583 2 925 3 488 0 989 1 303 3 517 4 861 2 769 0 494 6 179 3 987 0 497 5 985 0 695 5 973 2 989 L det 3 39 61K 18 15K 32 34K 13 47K L det ector 0 68K 78 1
106. ves or sent via ftp to one s home institution Depending on the amount of header information a single FITS file of a 512 X 512 image is about 1 057MB and a single 4 color exposure is 4 images 4 2MB Under the present version of WILDFIRE data acquisition e At the 4 m SQIID is accessed from the Linux workstation tan which is the connected via VNC to the SQUD host Sun computer khaki e At the 2 1 m SQUID is accessed from the Linux workstation sapphire which is connected via VNC to Sun computer lapis which handles the SQIID host Sun computer royal remotely It is interesting to note that the current arrangement allows SQIID operations to be viewed remotely However since hosting multiple VNC connections places an undue burden on the Sun systems this is not recommended for continuous useage A separate Linux based system serves as the telescope control with a terminal at the LTO station a hardwire link between the TCS and instrument control computers is used to send TCS commands to the telescope singly or within TCL scripts and to retrieve telescope information for the image header A schematic depiction of this arrangement is shown in Fig 3 Instrument Rotator Manual Cold pap SQIID Electronics Kowen DarkSlide Sean ii 2 p 2 soueppes FDET of ree nr Optics T Heurikon DSP o amp 3 a h Y i Telescope Reduction gt Instrument Computer Computer

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