User`s guide (Acrobat pdf format)
Contents
1. DIGIT_O BMP DIGIT_1 BMP DIGIT_2 BMP DIGIT_3 BMP DIGIT_4 BMP DIGIT_5 BMP DIGIT 6 BMP DIGIT 7 BMP DIGIT 8 BMP DIGIT 9 BMP PERIOD BMP MINUS BMP COLON BMP BLANK BMP CLEA32 ICO RADTEL ICO Pulsar Data Section V 2 PULSARS DAT PULSARS TXT HOTPLSRS LST 16 color versions of the above bitmaps Characters for the simulated LED displays Icon for the Radio Astronomy of Pulsars exercise Icon for the receiver windows Data for 558 pulsars Description of data in PULSARS DAT A finding list of interesting pulsars This list may be modified during program execution see discussions of parameters Write Hot List File and Exact Pos for Hot List in Section V 1 1 Help and Related Files Section V 3 in General Users Guide to CLEA Windows Software CLEAHELP HLP PULSRHLP LST PULSRLAB HLP PLSANHLP LST PULSRANL HLP PLSLSHLP LST PULSRLST HLP REMINDER PLS Text for Help gt On Help Topic Index List for Help on using radio telescope and receivers Text for Help topics on using radio telescope and receivers Topic Index List for Help on Data Analysis features Text for Help topics on Data Analysis features Topic Index List for Help on Pulsar List features Text for Help topics on Pulsar List features Text to display when Exit selected Version 1 0 IV 2 Files Generated During Execution The following files are generated during execution of this exercise Fi2. recordings of pulsar sounds made by various astronomers at Arecibo Although we made no attempt to analyze these technically they served as the basis for our simulation in that we simply listened to them and then attempted experimentally to create a similar sound PAGE 17 Student Manual The resulting technique for the generation of each sound sample point is as follows 1 Data corresponding to the correct phase is taken from the pulse data table Section VI 1 Since the interval between sound samples is much less than the table increment 1 5512 as compared to 1 25 to 1 800 second interpolation of the table values is required 2 Frequency from the main receiver setting antenna and attenuation factors as well as background noise are applied in a manner similar to that described in Section VI 1 3 for the video signal Scaling is applied to yield values in the range 0 255 for storage in 8 bits Occasional values above 255 are truncated 3 If the sound buffer is filled with the values generated in Step 2 the resulting pulse sound is unsatisfactory a barely audible whoosh unlike the distinct chuff heard on the pulsar recordings However it was discovered that the simple technique of multiplying each point by function Random which returns a random real number in the range 0 0 1 0 before scaling yields a sound that is remarkably similar to the recordings If desired the user can alter the effective bandpass of the gene
3. sound Please read Section VI 2 3 2 before modifying this value The default is 0 92000 Sound Sample Rate The sampling rate for the generated sound Increasing this value raises memory RAM usage by increasing the size of the sound buffers see Section VI 2 The default rate is 5512 Hz Telescope Type This software will simulate three types of telescope fully steerable which can be pointed to any spot in the sky above the local horizon meridian transit which can be slewed only in declination and Arecibo type which can be pointed only within a few degrees of the local zenith The default is fully steerable Also see Horizon Limit and Limit Slewing Pace 8 Version 1 0 Pulsar Identification This option instructs the software to identify the current pulsar by its J2000 positional designation its B1950 designation or not to identify the pulsar The pulsar identification appears on the receiver window when there is a pulsar in the beam and on recorded data The default is the B1950 designation which is the most commonly used Demonstration Mode This option is provided for those who may wish to avoid the login process when using this software as a demonstration When this switch is on the Run selection as well as Login both under File on the main menu are enabled when the program starts If Run is then selected before Login the program proceeds as if the login process had actually occurred In this case the 1st login name is se
4. them significantly smaller is impractical for a number of reasons and is likely to create more problems than it would solve any synchronization changes made through the buffers will occur only after noticeable delays Pace 18 Version 1 0 The net result is that there is no direct method we are aware of to keep the video and sound in step at all times On the other hand the out of sync condition is generally noticeable only with the longer period pulsars greater than 1 2 second and as noted earlier is not a significant problem on the newer Pentium PCs Additional information on sound video synchronization is provided below as follows The techniques used to introduce the dispersion delay and other changes into the sound stream when the receiver frequency is changed are described in Section VI 2 3 1 while Section VI 2 3 2 outlines a process by which the user can make some improvements to the synchronization by altering the display rate VI 2 3 1 Synchronizing After Frequency Changes If the frequency of the main receiver is changed while the receiver and pulsar sound effects are active several changes generally occur in the received signal that must be reflected in the sound In particular the pulse strength and background noise level change and the difference in the timing delay due to the dispersion effect at the old and new frequency results in a phase shift in the received pulse Since the video display is generated point by
5. these buffers are simply recycled i e immediately sent back to the sound system without change as they are returned Allthree pulsar sound buffers are flagged for regeneration when there is a 196 or greater change in the signal attenuation 1 e tracking is off and the pulsar is drifting into or out of the field Flagged buffers are regenerated one at a time as they are played and returned by the sound system e All three pulsar sound buffers are similarly flagged for regeneration when there is a change in the receiver frequency In this case appropriate timing delays are calculated from the dispersion Section VI 1 1 3 and introduced via extra buffers filled with noise only see below e The three remaining buffers are held in a pool and used to introduce timing delays see Section VI 2 3 When needed a buffer is selected its data length is established by the required delay time and it is filled with noise only When any of these buffers are returned from the sound system they are flagged as available and returned to the pool until needed Allocating these buffers initially and holding them until sound generation is finished avoids any overhead associated with repeated memory allocation deallocation VI 2 2 Simulating the Pulse Sound The sounds made by pulsars as recorded via radio telescopes depend on several factors one of the most important being bandpass We are fortunate to have in our possession thanks to J H Taylor
6. 1 We have made one minor modification to this data the D exponent notation FORTRAN double precision floating point where it occurs has been changed to E for compatibility with Pascal I O The generation of the observed pulses and periods from the pulsar data is described in Section VI 1 Also see Access Pulsar List in Section V 1 1 Table V 1 Pulsar Data Used Name Description Jname The J2000 Pulsar Name Bname The B1950 Pulsar Name RA2000 The J2000 Right Ascension in Decimal Degrees DEC2000 The J2000 Declination in Decimal Degrees P The Barycentric Period in Seconds Pdot The Barycentric Period Derivative in Sec Sec PEpoch Epoch of the Barycentric Period MJD TBg Sky Background Temperature in K DM Dispersion Measure in pc cm w50 Profile Width at 50 of Peak in ms s400 Time Averaged Flux Density at 400MHz in mJy s600 Time Averaged Flux Density at 600MHz in mJy s1400 Time Averaged Flux Density at 1400MHz in mJy Pac 11 Student Manual V 2 2 Pulsar Hot List File The Pulsar Hot List File is a finding list of names and positions of pulsars selected for study along with pertinent comments Although the Hot List File may be modified off line with a text editor items are normally added to or deleted from this list through the exercise software see discussions of parameters Write Hot List File and Exact Pos for Hot List in Section V 1 1 and the Hot List file name parameter in Section V 1 3 The format of th
7. Radio Astronomy of Pulsars Software Users Guide A Manual to Accompany Software for the Inductory Astronomy Lab Exercise Document UG 8 Version 1 RADIO ASTRONOMY OF PUESARS A LABORATORY EXERCISE IN ASTR NOMY Department of Physics Gettysburg College Gettysburg PA 17325 Telephone 717 337 6028 email cleaQ gettysburg edu Contemporary Laboratory Experiences in Astronomy Contents iMi eR MPD Purposes e e Roe bte edet ete e acetic eerie tetti eet 3 F2 Acknowledgments e ete ep eaten eemper etaed 3 Il System Requirement s oie ee sienne epo too a end na nee Yo epu ia vu oov rana estss easto eie S rN ES E S HI Installation and Operation M M S M i Network Installation zero titer eee er soos eds Cabos ECOL ca Sas be Bae Se da ben SE OP ae URES Ria Soa ee boos 5 IV Files Included With This Exercise 225 rmiisscstn eth sovsossctuaasscics x vig dd er ber vv vea Cuin bela EX V e IX UID s Rye dE D IV 1 Files Created During Installation eseeeeeeeeeeeeeeeeee eene nennen terere nee nete enr eren entren nennen 5 1V 2 Files Generated During Execution eer tei ce e e tete te eee 7 IV 2 1 Naming PLR and CSV Files apite e a O aE etre eterne aa Eae ain treten enne 7 borde ure O V Parameters and Selectable Options sees eene netten etre ete nn eterne trennen 8 V 1 1 Simulation Options and P
8. arameters oiis essione srren enne ene rennen enne en nennen trennen trennen 8 V 1 2 Time and Location Parameters eese eene enne enr enne teen nen ne enren trennen treten treten 10 VDSS Bile IName Optom nip rte Rire ene eene Por RO Pietre es se ee RE OI 10 N22 Data Tesi i URSUS apte epo eae ar eee 11 N22 Pulsar Data Files iue repete e tr delle e Ree e I GER e emet 11 V 2 2 Pulsar Hotlist File BS BEE eene nap gti tu ipe 12 V22 3 Recorded Signal Data File 5 intem tee re n ted te epe EP ete ee ec eee tes 12 V 3 Using a Spreadsheet Program snie r a aaa aa E nnne E E E ne E aE rete entente entente entren 13 VI ASTRONOMICAL DATA MODELS AND ALGORITHMS c eeeeeeeeeneennenneenees 14 VIEL Pulsar Signals iiie Re e tede ones as Siete ee E E REPE pite 14 MET Pulse Date eoe eA him eee ar eee Rae Ai aes 14 VI 1 1 1 Pulsar Period and Phase oreet tee Hr e tr eer en te dens 15 VI 1712 Pulse Profiles 5 ete ee OO HER REGE UU I eere e ante ee ope 15 VI 1 1 3 Pulse Dispersion iie eret ete eo P eR e e e ep EEES 15 VEI 2 Background and Noise 5 e ehe te ot et iet ste eve et eee dete 15 VI 1 3 Generating the Signal eee etae eem ep bie a PER k eget 16 VIE2 Pulsar Sound Effects z 1 ae et Rag nte del E EIN IE E OR Ur deed aae 16 VE2 1 General Technique eee RE PRU EH eau yach sas e ea e Reste Reate 16 VI 2 2 Simulating the Pulse Sound siis iiis mera seeen r iee EE eee een
9. b This number then appears as the default on the Login dialog The table number has a maximum length of 4 characters but need not be numeric PAGE 9 Student Manual Password This is the password for access to the Options dialog Allowable passwords have a maximum length of 16 characters and are case sensitive The default password is CLEA V 1 2 Time and Location Parameters The following station location and local time parameters appear on the window titled Time amp Location Parameters To access this dialog press the button labeled Station on the Startup Parameters Options window Location Name description of the observatory or radio telescope 79 characters max The default is Gettysburg College Radio Observatory Longitude Longitude of the radio telescope The default is 79deg 13min 56sec West Latitude Latitude of the radio telescope The default is 39deg 49min 52sec North Local Time Difference UT minus local zone time in hours for the observatory The default is 5 hours Eastern Standard Time Altitude Altitude of the observatory or station in meters The default is 176 8 meters V 1 3 File Name Options The following file and path name parameters appear on the window titled File Name Options To access this dialog press the button labeled Files on the Startup Parameters Options window See the General Users Guide to CLEA Windows Software for discussions of Windows bitmap BMP files inclu
10. cords in the file beginning with record 5 is lt 1601 Table is located on the following page Pace 12 Table V 3 Recorded Signal Data File Record Format Version 1 0 Record Field 1 Format 1 Pulsar ID B1950 or String 12 J2000 2 Revr 1 Frequency Decimal 2 MHz 3 Revr 1 Gain 0 125 8 0 Decimal 3 4 Start Time Julian Day Decimal 8 minus 2 400 000 5 Revr 1 Signal at TO Decimal 3 6 Revr 1 Signal at TO Decimal 3 Delta T etc Field 2 Telescope Aperture Meters Revr 2 Frequency MHz Revr 2 Gain 0 125 8 0 Delta T between data records Seconds Revr 2 Signal at TO Revr 2 Signal at TO Delta T Format Integer Decimal 2 Decimal 3 Decimal 8 Decimal 3 Decimal 3 Field 3 Number of Slave Receivers 0 2 Revr 3 Frequency MHz Revr 3 Gain 0 125 8 0 Revr 3 Signal at TO Revr 3 Signal at TO Delta T Format Integer Decimal 2 Decimal 3 Decimal 3 Decimal 3 V 3 Using a Spreadsheet Program This software provides the following features to expedite students use of a spreadsheet program for data reduction and analysis 1 Measurements made in the Data Analysis window may be saved in files CSV that are formatted for import into most commercial spreadsheet programs 2 If an available spreadsheet program is identified in the Spreadsheet Program File field on the File Name Options dialog see Section V 1 3 t
11. ction VI 1 1 If the receiver is operating at a frequency other than the base frequency the dispersion Section VI 1 1 3 is used to calculate a time offset which in turn yields an offset in the index used to access the table The index is adjusted as needed to keep it within the bounds of the table rollover rollback 2 Ifthe Beam Width parameter Section V 1 1 is zero an attenuation factor is computed from the offset of the pulsar from the center of the beam This computation employs the half power beam width calculated from the antenna aperture and frequency and assumes an exponential drop off in signal strength away from the beam center If the Beam Width parameter is non zero the signal is taken at full strength anywhere within the beam and zero outside of it 3 An antenna factor is computed from the square of the Antenna Aperture parameter The antenna and attenuation factors are applied to the value from Step 1 4 The pulsar flux at the receiver frequency is obtained by simple interpolation from the s400 s600 and s1400 values see Table V 1 Three point interpolation was attempted but abandoned when it was frequently found to yield negative fluxes at intermediate frequencies A frequency factor is computed from the ratio of this flux to the s400 value and applied to the value from Step 3 5 The background signal Section VI 1 2 is computed and added to the results of Step 4 yielding the total signal VI 2 Pulsar Sound Ef
12. ding logo and title screens and color issues Pace 10 256 Color Logo A 256 color bitmap for the CLEA logo screen The default is CLEALOGO BMP 16 Color Logo A 16 color bitmap for the CLEA logo screen The default is CLEALG16 BMP 256 Color Title A 256 color bitmap for the exercise title screen The default is PULSRLAB BMP 16 Color Title A 16 color bitmap for the exercise title screen The default is PULSRL16 BMP 256 Color View A 256 color bitmap for the control panel view screen The default is NRAOGBTV BMP 16 Color View A 16 color bitmap for the control panel view screen The default is NRAOGB16 BMP Pulsar Data The pulsar data file see Section V 2 1 The default is PULSARS DAT Hot List The hot list file see Section V 2 2 The default is HOTPLSRS LST Main Help List An index list of Help topics see General Users Guide to CLEA Windows Software for the main window telescope controls and receivers The default is PULSRHLP LST Analysis Help List An index list of Help topics for the Data Analysis window The default is PLSANHLP LST Pulsar List Help List An index list of Help topics for the Pulsar Parameters window see Access Pulsar List in Section V 1 1 The default is PLSLSHLP LST User Help File Site specific Help information available under Help gt User see General Users Guide to CLEA Windows Software The default is no entry Version 1 0 Reminder File Text
13. e dispersion measure its units are parsecs cm see Table V 1 This delay is calculated and applied when displaying pulse data at other than the base frequency of 400 MEZ as described in Section VI 1 3 VI 1 2 Background and Noise The background signal includes contributions from both the sky and the instrument antenna detector etc The base level for each component at the receiver frequency is obtained from Planck s Law using TBg Table V 1 for the sky temperature and the Detector Temperature parameter Section V 1 1 for the instrument A factor reflecting the size of the antenna see Antenna Aperture parameter Section V 1 1 is calculated and applied to the instrument contribution The Background Base parameter Section V 1 1 yields a factor that is applied to the sum of the background components Pack 15 Student Manual This parameter may be used to adjust the overall background level Poisson noise is applied to the background signal via function POIDEV XM which returns an integer value that is a random deviate drawn from a Poisson distribution of mean XM Press et al Ch 7 This function is also used to noise the pulsar signal see Section VI 1 1 2 VI 1 3 Generating the Signal The following steps outline the process employed to generate each point of the displayed signal for each active receiver l Ifthe receiver is operating at the base frequency 400 MHz the next point is taken from the pulse data table Se
14. e ener ene enne nennen nente tret nenne tenes 17 VI 2 3 Synchronizing Sound and Video eese eene ener ennen eren Ee Saser ERE ipoe 18 VI 2 3 1 Synchronizing After Frequency Changes eeesseeseeeeeeee nete nennen nete ene 19 VI 2 3 2 Adjusting the Display Rate 1 ete P EE EE pee E pb i eE E E a ios 19 Version 1 0 I Introduction I 1 Purpose This document provides specific technical information for users of the CLEA software module Radio Astronomy of Pulsars It includes discussions of hardware and operating system requirements Section ID software installation and operation Section IID files associated with the exercise Section IV user options and file formats for possible user modifications Section V and astronomical data models and algorithms employed in the exercise Section VI The material in this guide is intended for use by the instructor and by other personnel involved in installing and configuring the exercise software and PC hardware It is not intended for distribution to the students The word user when it appears herein should be interpreted as instructor and not student Readers of this document are assumed to have available the General Users Guide to CLEA Windows Software which contains technical information that applies to all CLEA Windows software Much information contained therein is not repeated here In cases of conflicting information this guide should be co
15. e file records is given in Table V 2 data items in each record must be separated by at least one space Numeric items may be either integer or decimal see Note below string items must be enclosed in single quotes Table V 2 Hot List File Record Format Field Description Format 1 Pulsar ID B1950 or J2000 String 12 2 Right Ascension Hours Numeric 3 Right Ascension Minutes Numeric 4 Right Ascension Seconds Numeric 5 Declination Degrees Numeric 6 Declination Minutes Numeric 7 Declination Seconds Numeric 8 Comment String 40 Note The numeric quantities for Right Ascension and Declination may be entered using any combination of decimal and integer quantities as long as all fields are present use 0 for unused fields For example a Right Ascension of 12h 14m 23 2s may be entered as 12 14 23 2 12 14 3867 0 or 12 239778 0 0 V 2 3 Recorded Signal Data File Recorded Signal Data files normally given the extension PLR see Section IV 2 are created when recorded radio signals from pulsars are saved These files are later read in and analyzed using the facilities of the Data Analysis window The format of the file records is given in Table V 3 For decimal data items the number in parenthesis is the number of digits to the right of the decimal point Data items in the records are separated by commas Although in Text format these files would not normally be edited off line The number of data re
16. e it to fall behind the sound These glitches appear more frequently when more than one receiver is active and are undoubtedly caused by momentary processing overloads on either the CPU or the video system Ideally one would like the software to be self correcting That is to establish some link between the sound and video systems that would keep them synchronized or at least quickly restore synchronization if it is lost Unfortunately factors which preclude this type of approach include the following 1 The video display is generated point by point by the software Thus the software is always in control of the state of the display The sound on the other hand must be pre generated in buffers and sent to the sound system which is in complete control of playing it 2 The sound system operates independently and in real time which it must to avoid gaps or distortions The video system is subject to waits and interruptions which may be generally insignificant to most applications but are sufficient to cause the loss of synchronization 3 There is little direct control of the sound once a buffer has been sent There is no direct command to start playing or especially stop wherever you are and play the next buffer immediately You cannot stop playing in the middle of a buffer 4 Since at any given time the sound system is holding two buffers one playing and one waiting and the buffers average one to two seconds in length making
17. ed radio signals from pulsars are saved for later analysis Names for these files are generated from the first login name Student 1 as described below Section IV 2 1 The format of these files is described in Section V 2 3 CSV A file with extension CSV is written when Results gt Save Recorded Measurements is selected from the Data Analysis menu The file name is generated from the first login name see Section IV 2 1 below This file is written in a format Comma Separated Values that can be used as input to most commercial spreadsheet programs See Section V 3 for information about using a spreadsheet program with this exercise and the contents of the CSV file Note Files PLR and CSV should be periodically deleted from the working directory when they are no longer needed This can be done under DOS or via the Windows Explorer File Manager IV 2 1 Naming PLR and CSV Files Names for the student generated PLR and CSV files are created from the first login name Student 1 If the login entry includes both a first and last name the first letter of the name is combined with the first seven if present letters of the last name If only one name is entered the first eight if present letters are used For subsequent files the name is truncated if necessary to five characters A three character running number is then added along with the extension Examples Login Name File Names Annie Jump Canno
18. etain access to the options Select Yes Select File gt Run gt Radio Telescope Turn tracking on then point the telescope at a strong pulsar with a period of a second or more You can use the Hot List for this Pulsar 0608 28 is a good choice Access the receiver and begin receiving Note any phase difference between the sound and video You may want to open additional receivers if you will normally have more than one receiver active Close the receiver and select File gt Preferences Enter a new value for Sound Sync Factor If the sound appeared in Step 5 to be running ahead of the video enter a larger value like 0 93 for the factor In the unlikely event that the sound is behind the video decrease the value of the factor Make only small changes As a data point a 50 MHz 486DX machine that we use for testing operates best with a sound sync factor of 0 935 Iterate Steps 5 amp 6 making smaller and smaller changes until a satisfactory synchronization is achieved Be sure you save the last change to the options that you make You may also want to record it so you can set other similar machines without the iteration process It bears repeating that sound video synchronization difficulties stem from a number of factors as discussed in Section VI 2 3 This adjustment affects only one of them If you often experience an out of sync condition and wish to minimize the possibility while still retaining the sound effects for examp
19. fects In order to enhance the realism of the simulation and to reinforce in the students the idea that a pulsed signal is being received we have included sound effects in the exercise software The sound feature is implemented through the WaveOut family of Windows API functions the general technique employed is presented in Section VI 2 1 In Section VI 2 2 we describe our method of simulating the sound of actual pulsars Certain characteristics of the WaveOut interface make it difficult to maintain synchronization between the sound and video display under all circumstances especially on slower 486 386 machines This issue is discussed in Section VI 2 3 Generation of the pulsar sound effects requires the presence of a Sound Blaster compatible audio card 8 bit is sufficient and speakers Unfortunately we encountered technical difficulties that we have so far been unable to resolve in integrating the sound features into the 16 bit version of the software This capability is therefore available currently only in the 32 bit version for Windows 95 NT VI 2 1 General Technique The Windows API facilities for producing sound require that sound buffers or pages be allocated filled and passed to the sound system via function WaveOutWrite Each buffer is played in its entirety and then passed back via a callback routine for reuse or deallocation Multiple buffers are necessary to assure uninterrupted sound Pace 16 Version 1 0 Spec
20. field regardless of the Beam Width setting The default is Off Sound Features This option activates the sound features provided that the software detects a viable sound card The sound features are not available in the 16 bit version of the software see Sections II and III For the 32 bit software the default is On Test Mode In test mode slewing to specified coordinates and hot list positions is instantaneous and the Preferences menu selection for user options is always enabled Instructors may find this mode useful for demonstrations and in creating verifying exercises The default is Off Also see Demonstration Mode and Access Pulsar List Access Pulsar List When this option is set the user has access to the pulsar list data see Section V 2 1 via a selection on the main menu File gt Pulsar List The selection doe not appear until the telescope control window has been activated The Pulsar Parameters window displays all quantities used by the program see Table V 1 and includes facilities for searching for pulsars by name and calculating values of the period as a function of the date and distance as determined from the electron density This feature is intended to assist instructors in developing observation lists for exercises and verifying student results and may also be useful for demonstrations The default is Off Lab Table Number This field allows the instructor to preset the table number for each machine in the la
21. he spreadsheet may be accessed directly from the exercise Selecting Results gt Save Recorded Measurements from the Data Analysis menu causes recorded measurements to be written to a file qualifier CSV that is suitable for import into a spreadsheet program In addition to recorded measurements records in this file also contain relevant information from the recorded signal data being measured The format of the data records in the CSV file is given in Table V 4 For decimal and floating point data items the number in parenthesis is the number of digits to the right of the decimal point Prior to the data records the file contains records which include the date and time table number login names and column headers Data items in the records are separated by commas strings are enclosed in single quotes See Table V 4 on the following page Pack 13 Student Manual Table V 4 Measurements File Record Format Field Data Type Field Data Type Pulsar ID B1950 or J2000 String 12 Data Start Time Julian Date minus Decimal 8 2 400 000 Receiver Frequency MHz 400 0 1400 0 Decimal 2 Comment added when measurement String recorded Receiver Gain Relative 0 125 8 0 Decimal 3 Number of Data Records in Recorded Signal Integer Data Reference Cursor Reading Seconds Decimal 6 Delta T from Recorded Signal Data Decimal 2 Milliseconds Vertical Cursor Reading Seconds Decimal 6 Telescope Aperture Meters Integer Horizontal Cu
22. ia ftp download IN31 PLS EXE Contains and installs the 16 bit version for Windows 3 1 3 11 see Note below This module is distributed on floppy disk IN95 PLS EXE Contains and installs the 32 bit version for Windows 95 NT This module will not execute under Windows 3 1 3 11 This module is distributed on floppy disk Note The installation program IN31 PLS EXE as well as the 16 bit version of the exercise software will operate under Windows 95 NT but we recommend that the 32 bit version be used especially since the 16 bit version does not contain the sound features To install the exercise software from a floppy disk 1 2 Place the distribution diskette in a floppy drive This will be either drive a or drive b Using the File Manager or Windows Explorer access the floppy drive A or B and verify that you have the correct installation module for your operating system IN3 1_PLS EXE for Windows 3 1 3 11 IN95_PLS EXE for Windows 95 NT If the version is correct double click on the program entry IN31 PLS EXE or IN95 PLS EXE in the File Manger Windows Explorer display To install the exercise from a downloaded module 1 Using the File Manager or Windows Explorer locate the module INST_PLS EXE You will have placed this module in some directory folder such as C SAVSTUFF CLEA when you downloaded it If you are running Windows 95 you can select Tools gt Find gt Files or Folders from the Windo
23. ifics of the pulsar sound implementation in this software are as follows 1 Initially six buffers are allocated Three are used on a rotating basis for the pulsar sound the remaining three are employed as needed to introduce timing delays see Item 4 below 2 To minimize memory RAM requirements the sound buffers are sized as follows e 8 bit monaural sound 1 byte per sample is employed This was found by experiment to be entirely adequate and also minimizes requirements for the user s sound card e A sampling rate of 5512 Hz giving a maximum sound frequency of 2756 Hz by the Nyquist criterion the maximum sound frequency is 1 2 the sampling rate was found to yield satisfactory pulsar like sounds Section VI 2 2 as well as moderately sized buffers e Ifthe period of the pulsar is less than 0 5 seconds then each pulsar sound buffer holds about two seconds of sound exactly Round 2 Period Period Otherwise each buffer holds one period of sound See the discussion of buffer length in Section VI 2 3 3 Pulsar sound buffers are generated from the pulse data table Section VI 1 as described in Section VI 2 2 below 4 Tominimize computational overhead and the risk of possible gaps in the sound or delays to concurrent processes primarily the video display the sound buffers are re generated only in the following situations All three pulsar sound buffers are filled when the receiver is started Under normal conditions
24. le during a demonstration take note of the following Avoid changing frequencies when the receivers are active expecially if more than one receiver is open Set all receivers to desired frequencies before pressing the Mode button to begin receiving Do not operate receivers with the telescope tracking turned off This situation creates the greatest processing overhead because the sound buffers must be continually regenerated as the signal attenuation changes REFERENCES Kraus J D Radio Astronomy 2 Ed Cygnus Quasar Books Powell Ohio 1986 Press W H Flannery B P Teukolsky S A and Vetterling W T Numerical Recipes Cambridge University Press Cambridge 1986 Taylor J H Manchester R N and Lyne A G Catalog of 558 Pulsars Astrophys J Suppl 88 529 1993 Available on CD ROM in Selected Astronomical Catalogs Volume 2 Astronomical Data Center NASA Goddard Space Flight Center Greenbelt MD 1995 Pace 20
25. les CLEALOG LOG and PLSROPTS INI are automatically created files with extensions PLR and CSV are created on option as noted For a discussion of the placement of these files path and folder directory see Section III 3 3 in the General Users Guide to CLEA Windows Software CLEALOG LOG A record that includes the program name CLEA PLS the date and time and the names and table number from the Login dialog is appended to this file whenever the exercise is started and when it is terminated This file is in text format and can be read and or printed at any time Since this file can grow without limit it should be deleted from time to time via DOS orthe Windows Explorer File Manager A new file will then be started at the next login This file can optionally be given a different name see Section V 1 3 Note A logout record will be written to this file only if the students exit correctly from the program select File gt Exit from the main menu or close the main window from the System Menu or X box They should be instructed to do this rather than simply abandoning the computer or turning it off PLSROPTS INI Current settings for file names and options This file can be deleted if desired it will then be re created from internal defaults when the program is run If the options are updated see Section V 1 the previous version is saved as PLSROPTS BAK PLR Files with the extension PLR are written when record
26. means of improving the overall synchronization between sound and video by altering the sound rate The parameter actually represents the ratio of the generated sound rate to the generated video rate The default determined by experimentation and found to hold on several machines covering a range of processor speeds is 0 920 This implies that the video signal display normally runs at a rate slightly faster than real time If you are having sound video synchronization problems that seem to be due to a difference in the rates you can make adjustments to this parameter You should read Section VI 2 3 before making any changes Complete synchronization may not be possible Note a difference in the video and sound rates will manifest itself by the sound and video drifting in and out of synchronization at a constant rate over time Adjusting the Sound Sync Factor will not correct a phase shift a time difference between the sound and video pulses that remains nearly constant although stopping and restarting the receiver often will Pace 19 Student Manual To synchronize the sound and video rates I 2 Start the software You should have a minimum ideally zero of other programs open Log on as instructor and enter the password to access the options At this point you can enter your first guess for a new Sound Sync Factor see Step 6 and press OK or you can simply press Cancel A screen will appear asking if you want to r
27. mit The limiting height above the local horizon in degrees for telescope slewing see Limit Slewing The default is 10 0 Antenna Aperture The aperture of the simulated radio telescope in meters The default is 100 Base Slew Rate The base slew increment in arc seconds applied at each slew timer message This value is multiplied by the slew rate factor set from the control panel The default is 50 Base Gain Factor This factor can be used to adjust the overall receiver gain The default is 1 00 Background Base This factor sets the overall background level The received background is adjusted for background temperature in the field 1f known detector temperature and receiver frequency see Section VI 1 2 The default is 5 Beam Width The effective telescope beam width in degrees If this value is zero the half power beam width HPBW is calculated from the telescope aperture and receiver frequency and an attenuation factor is applied if the pulsar is not at the center of the beam see Section VI 1 3 Setting this parameter to a non zero value makes it easier for students to locate objects using coarse telescope pointing The default is 0 zero Detector Temperature The effective temperature K of the detector system This establishes the level of noise contributed by the detector see Section VI 1 2 The default is 50K Sound Sync Factor This parameter is used to adjust the synchronization between the video display and the
28. n ACANNON CSV ACANNO01 PLR Martin Schwarzschild MSCHWARZ CSV MSCHWO012 PLR Galileo GALILEO CSV GALILO005 PLR If the first login name is blank the files are named NOLOG xxx CSV PLR PAGE 7 Student Manual V User Options and Data This software has been designed to provide the user with a great deal of flexibility in configuring the facility for specific needs Users may adjust simulation parameters specify telescope type select from a list of optional features change the station location specify alternate bitmaps for display modify the Help facility attach a spreadsheet program and modify the underlying pulsar data Details of the facilities providing this adaptability are given in Sections V 1 through V 3 below V 1 Parameters and Selectable Options In all CLEA software modification of control parameters and options is accomplished through an options dialog that is accessed from the login dialog via a password Details of this feature including the password access are provided in the General Users Guide to CLEA Windows Software Due to the number of modifiable features associated with this exercise the options facility comprises three dialog windows as detailed in the Sections that follow V 1 1 through V 1 3 V 1 1 Simulation Options and Parameters The following switches and parameters appear on the window titled Simulation Options which appears as the main dialog when the options facility is accessed Horizon Li
29. neration of the pulse data table combined with other initialization activities may result in a considerable delay on machines with 386 processors when the receiver Mode button is pressed or a pulsar drifts into the field Unless otherwise defined all parameters in the discussions that follow are found in Table V 1 Section V 2 1 VI 1 1 1 Pulsar Period and Phase To find the current period of the pulsar we compute the quantity DelP from DelP DelT PDot where DelT is the current Julian Date minus PEpoch converted to seconds Then PCurrent P DelP To find the current phase we compute the mean period from PMean P DelP 2 The phase is then the fractional part of DelT PMean Since we want the initial phase to be 0 5 we compute DelPhase 0 5 Phase The observation start time see Table V 3 is then set to the current Julian Date DelPhase PDays where PDays is PCurrent converted to days This process assures that separate observations made at time intervals of hours or even days can be combined to determine periods to high accuracy VI 1 1 2 Pulse Profiles Pulse profiles are simulated by a Gaussian profile The parameter W50 is used to set the standard deviation while the parameter s400 sets the pulse strength various scale factors some of them arbitrary are applied At each time step the phase change since the last step is determined and the integral of the Gaussian function over that range is evaluated normali
30. nsidered definitive for the Radio Astronomy of Pulsars software In particular please note that this software is distributed in a different form than previous CLEA modules see Section III for details I 2 Acknowledgments Development of CLEA exercises and materials including this guide is supported in part by National Science Foundation Grants USE 9155927 USE 9354514 and DUE 9652801 and by Gettysburg College II System Requirements This software runs under Microsoft Windows and is distributed in two versions a 16 bit application for Windows 3 1 3 11 and a 32 bit application for Windows 95 NT Details concerning the available distribution formats are given in Section III A minimum of 8 Mbytes of RAM 16 Mbytes for Windows 95 NT is recommended although smaller configurations down to 4 MB for Win3 1 3 11 and 8 MB for Win95 NT may prove sufficient A color SVGA video controller and monitor is required A full installation will require about 3 Mbytes of hard disk storage A Sound Blaster compatible 8 or 16 bit sound card and speakers are required for the sound features which are available only in the 32 bit version Users may find that PCs employing 386 processors while usable are not fully adequate for this software In particular considerable delays may be experienced at certain points such as when the Mode button on the receiver is pressed to begin receiving a signal A 486 processor is generally satisfactory with the exception
31. of pulse profiles and the effect of dispersion is described in Section VI 1 1 below Section VI 1 2 covers the determination of background levels and noise while Section VI 1 3 describes how the components are assembled to yield the signal strength as a function of time and frequency VI 1 1 Pulse Data In order to minimize the amount of calculation required at each time step so that the display is generated at as close to a real time rate as possible the basic pulse data is pre generated and placed in a table when the Mode button on the receiver is pressed to switch the mode to Receive This also occurs when the telescope tracking is turned off and a new pulsar drifts into the telescope field The generated table holds a maximum of 2000 points the time interval between points is the same as on the receiver display and is determined from the Horz Secs parameter Since the receiver display has 400 points the generated pulse data is sufficient for nearly five full screens before wrapping is required The maximum time interval covered is 2 5 to 80 seconds depending on the Horz Secs setting The start time and rollover point of the data are adjusted so that the initial and final phase is 0 5 see Section VI 1 1 1 This guarantees that the data does not begin or end somewhere within a pulse Poisson noise Section VI 1 2 is applied to this data when it is generated but no sky or instrument background Pace 14 Version 1 0 Note The ge
32. point the effects associated with the frequency change appear immediately However due to its buffered nature the sound requires a few seconds to adjust The process is as follows also see General Technique Section VI 2 1 The three pulsar sound buffers are flagged for regeneration As they are played and released they will be refilled with sound data created at the new frequency 2 Adeltatis computed from the difference between the dispersion delay at the old frequency and the dispersion delay at the new Since timing adjustments are made by adding extra time in the form of noise to the sound stream any resulting negative delta t is made positive by adding time in increments of one period 3 A delay buffer of length delta t is generated and sent to the sound system This buffer contains noise only computed at the level appropriate to the new frequency The user will therefore generally observe the following on a frequency change 1 Although the video will change immediately the sound may emit one or more additional pulses at the old frequency 2 The noise level in the sound will then change to that of the new frequency One or more pulses may go by silently during this transition 3 Pulse sounds will restart synchronized with the video display The receiver will not accept additional frequency changes until this occurs VI 2 3 2 Adjusting the Display Rate The Sound Sync Factor parameter Section V 1 1 provides the user a
33. ral Users Guide to CLEA Windows Software with specific instructions for Windows 3 n and Windows 95 IV Files Included With This Exercise IV 1 Files Created During Installation The following files are compressed into the distribution file INST PLS EXE IN95 PLS EXE or IN31_PLS EXE Files not contained in all distribution versions are noted The compressed files are extracted and placed in the exercise folder directory during installation The list is grouped by function with references to related discussions in this document and the General Users Guide to CLEA Windows Software Software and Documentation README PLS Notes on the current version if any UPDATE PLS A list of updates by version since version 0 70 the first version to be widely circulated USRGUIDE PLS This document in text form CL32 PLS EXE 32 bit executable code for the exercise Distributed in INST PLS EXE and IN95 PLS EXE CL16 PLS EXE 16 bit executable code for the exercise Distributed in INST PLS EXE and IN31_PLS EXE Bitmap Files for Displays CLEALOGO BMP 256 color bitmap data for the CLEA logo screen PULSRLAB BMP 256 color bitmap data for the Title screen ARECIBO BMP 256 color bitmap image of the Arecibo telescope NRAOGBTV BMP 256 color bitmap image of the Greenbank GBT telescope PAGE 5 Student Manual PAGE 6 Bitmap Files for Displays Con t CLEALG16 BMP PULSRL16 BMP ARECIB16 BMP NRAOGB16 BMP
34. rated sound by varying the sampling rate see Sound Sample Rate parameter in Section V 1 1 The main effect of this is that more and more high frequency noise is added as the sampling rate is increased However buffer requirements increase the resulting sound begins to differ from the recorded pulsars and in addition higher sampling rates may exacerbate synchronization problems by increasing computational overhead Section VI 2 3 VI 2 3 Synchronizing Sound and Video The pulsar sound effects are generated using the frequency setting from the main receiver to establish pulse strength noise level and dispersion delay and are intended to synchronize with the main receiver video display However users may find that after a time the video and sound get out of sync In our experience this effect is rarely seen on machines with Pentium processors but is quite common on slower ones even the faster 486 models We suspect that the overall performance of the video card plays a significant role in this perhaps more than the CPU Unfortunately we have been unable so far to develop a complete solution to this problem We provide a means as described in Section VI 2 3 2 below of adjusting the overall video display rate to synchronize with the sound However a major problem in addition to the overall rate is the fact that the video display will sometimes not proceed smoothly but rather appear to undergo hitches or fits and starts that caus
35. rdless of whether or not you have a sound card and speakers PAGE 4 Version 1 0 If you upgrade to Windows 95 after installing this software you will retain the 16 bit version but switching to the 32 bit version is not difficult If you have only IN31 PLS EXE you will need to obtain either INST PLS EXE or IN95_PLS EXE if you already have INST PLS EXE you are ready to go Simply re run the installation as described above selecting the same destination folder and program group as before and the 32 bit software will be installed If you wantto conserve disk space you can then use the Explorer or File Manager to delete CL16 PLS EXE from the folder do not delete anything else III 1 Network Installation Installation of CLEA software on networks is described in detail in the General Users Guide to CLEA Windows Software Because this exercise is not distributed as a ZIP file you must run the installation program as described above to unpack the files For a network installation identify the appropriate shared drive when specifying the folder to hold the software Obviously you must have write privileges on the network drive when you do this Another technique is to install the software on any PC and then copy the entire contents of the program folder to the network drive Once you have done this you must create a local directory and install the exercise on all machines that will use it This process is described in Section III of the Gene
36. rsor Reading Relative this Float 4 Signal Data File Name String quantity has been factored by the receiver gain If the software finds an entry in the Spreadsheet Program File field on the File Name Options dialog Section V 1 3 the Spreadsheet item on the Results pop up Data Analysis menu is enabled Selecting Results gt Spreadsheet will then start the spreadsheet software If a file of recorded measurements has been saved immediately prior to accessing the spreadsheet that file will be automatically loaded when the spreadsheet appears If this is not the case or to load another file select File gt Open from the spreadsheet menu Be sure that the file type CSV is specified This might be located under a generic heading like Text Files Techniques differ depending on the spreadsheet used consult your documentation To return to the exercise either minimize the spreadsheet program or exit from it ASTRONOMICAL DATA MODELS AND ALGORITHMS VI 1 Pulsar Signals The simulated signal displayed and recorded as a function of receiver frequency is a sum of three components the pulse signal as a function of time the sky background as a function of sky effective temperature and the instrument background as a function of instrument effective temperature Poisson noise is independently applied to each of these components before they are combined The generation of pulse data including the determination of pulsar periods the simulation
37. t to Demonstration the file name base becomes DEMO and the Login menu selection is disabled The default is Off Also see Test Mode and Access Pulsar List Limit Slewing Ifthis switch is set the telescope cannot be slewed below the local horizon limit Turning this option on makes the exercise somewhat more complicated since the students must concern themselves with observation time local sidereal time etc The default is Off Fast Slewing This option activates the fastest slewing rate which is unrealistic for large radio telescopes Leaving this option on may help alleviate student complaints about having to wait so long especially if a number of observations are being made The default is On Plot Pulsar Positions If this option is set the positions of all the pulsars in the pulsar data file see Section V 2 1 will appear on the sky map displayed in the telescope control window The default is Off Write Hot List File This option allows the students to make permanent changes to the Hot List file If the option is off the students can modify the hot list as they wish during the exercise but cannot save their changes to the file The default is Off Exact Pos for Hot List This option assures that entries made to the hot list will carry the exact pulsar positions from the pulsar data file rather than the current telescope pointing coordinates This guarantees that pulsars accessed from the hot list will always be in the telescope
38. that there may be some difficulty keeping the sound synchronized with the visual display see Section VI 2 No problems that we are aware of have been experienced with Pentium processors III Installation and Operation Unlike previous CLEA programs which are distributed as ZIP files this software is distributed as a self extracting executable module that includes an installation program Three distribution formats are available as listed in Table III 1 Module INST PLS EXE contains both the 16 bit for Windows 3 1 3 11 and 32 bit for Windows 95 NT versions of the executable code as well as installation logic to determine and install the correct version without user interaction However this module is too large to distribute on a single 1 44 Mbyte floppy and is therefore available only for download from the CLEA ftp site io cc gettysburg edu You can also access this site through the World Wide Web Begin with the Project CLEA home page at www gettysburg edu project physics clea CLEAhome html For floppy disk distribution the two versions are separated Module IN31 PLS EXE installs only the 16 bit version while IN95 PLS EXE installs only the 32 bit version PAGE 3 Student Manual Table III 1 Software Distribution Modules Module Description INST PLS EXE Contains both 32 bit and 16 bit versions of the exercise software Determines and installs the correct version for the current operating system This module is distributed v
39. to be displayed when the students want to terminate the exercise see General Users Guide to CLEA Windows Software The default is REMINDER PLS Spreadsheet Program File The full name including path of a spreadsheet program to be accessed during the exercise for data manipulation and analysis see Section V 3 for details The file must be of type EXE or PIF and must be accessible from the student s computer in the drive and file specified example C MSOFFICE EXCEL EXCEL EXE This parameter is completely optional There is no default Log File A file text where log information is written during login and at termination of the exercise see Section IV 2 This file name can optionally include a full path presumably to a single shared log file which of course must be write enabled The default is CLEALOG LOG with no path designation V 2 Data Files Data files created and or used by this software are described in this section These files are in text format for ease of maintenance and modification as is the case with virtually all CLEA data files V 2 1 Pulsar Data File The Pulsar Data File includes the full Catalog of 558 Pulsars Taylor et al 1993 available on CD ROM in Selected Astronomical Catalogs Volume 2 A full description of this data is given in the file PULSARS TXT included with this exercise The file PULSARS DAT is identified therein as tablel dat The specific data fields used are listed in Table V
40. ws Explorer menu to help you locate INST_PLS EXE Double click on the program entry for INST_PLS EXE in the display Note Experienced Windows users will realize that there are means other than those described above to initiate the install program A quick method if you are certain of the path and file names is to select Start gt Run Windows 95 or File gt Run from the Program Manager menu Windows 3 x In the dialog box enter the path and program name such as A IN31_PLS EXE or C SAVSTUFF CLEA INST_PLS EXE and click on OK Use whatever method you prefer After the installation program starts it will ask you to select a folder directory in which to place the software and a program group for the icon If you have already created a program group for other CLEA software you will probably want to place this exercise there also Except for these selections the installation process is completely automatic and quite fast When it is finished an icon for the exercise should appear in the selected program group and on the start menu Windows 95 During installation program INST PLS EXE will determine the version of Windows that is present and install the correct CLEA software module There are some differences in appearance and functionality between the 16 bit and 32 bit versions In particular if you are running Windows 3 1 or 3 11 the 16 bit module will be installed and the sound features will not be available rega
41. zed so that the total area under the curve is 1 0 The value of the integral is then multiplied by the pulse strength to obtain the data point which is stored in the pulse data table after applying noise see Section VI 1 2 To speed the process a table of values for the Gaussian integral is generated initially by Simpson s Rule The integrals are then evaluated by interpolating the tabular values If the time increment is greater than 0 3 period the above process is not used Instead the number of pulses including fraction since the last step is computed and multiplied by the pulse strength This of course means that for the shortest period pulsars individual pulses will not be clearly delineated at longer time increments The time increment is determined by dividing the value of the Horz Secs parameter on the main receiver by 400 However the smallest possible value of the Horz Secs parameter 0 5 seconds is sufficient to accurately resolve pulses for all pulsars in the data file Section V 2 1 A number of pulsars exhibit a double peaked pulse profile This feature is not simulated by this software since there is no information in the pulsar data file see Section V 2 1 on which to base such a simulation VI 1 1 3 Pulse Dispersion The equation governing the delay between two frequencies f and f is 1 2 t t 4150 DM 1 f 1 7 where f and t are expressed in seconds and f and f in megahertz The parameter DM is called th
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