COMET SPECTROSCOPY AT HARTRAO <861128.1420> ======================================================== A set of programs has been developed to enable spectral line observations to be made on comets within the solar system. These programs are : 1. JULDA in a type 6 file on CR14 - run on the development computer. Returns the current Julian date. Useful for setting epochs when running TBCEG. Source file on cr 18 2. TBCEG permanently loaded in development computer. Provides predictions in three different forms for the comet, based on the user's prompts and parameters read from a disc file. See detailed notes below. Source file on lu 18 3. RACEP run from a type 6 file on the control computer. Tests operation of ACEPH, mimicing calls from ACOMT. The program is set to run on lu 1 . Source file on lu 18 4. ACEPH permanently loaded in control computer. Based on TBCEG, it returns the comet coordinates and radial velocity to the calling program. Called by RACEP and ACOMT. Source file on lu 18 5. ACOMT permanently loaded in the control computer. Based on ACFD, this is the spectral line observing program. It uses frequency switching, not position switching, for subsequent shift + folding of spectra. It does NOT permit scheduling of other programs. See detailed notes below for source file parameters. Source file on lu 18 6. OHCOM type 6 file , source on lu 18 Predict OH line strength from built in polynomial approximation to Halley Qoh and comet data read from source file, consisting of Julian date, geocentric distance, heliocentric distance, and the inversion. example of source file is OHCOMD::18 Disc files used by these programs : =================================== 1. comet parameter file, used by both TBCEG and ACEPH ; the latter ignores some parameters. eg HALLEY::16 2. The source file, used by ACOMT, contains the name of the comet parameter file, and equipment settings. eg OBSHAL::16 3. The output file for TBCEG, eg OUTPUT::14 Program TBCEG ============= THE TWO BODY COMET EPHEMERIS GENERATOR (TBCEG) IS A SELF- CONTAINED PROGRAM DESIGNED TO PRODUCE PREDICTED OBERVABLES OF A COMET FROM OSCULATING ELEMENTS THAT ARE INPUT BY THE USER. IT ACCOMPLISHES THIS THROUGH THE COMPUTATION OF A TWO-BODY ORBIT OF THE COMET FROM THE OSCULATING ELEMENTS AND THE COMPUTATION OF SOLAR COORDINATES FROM NEWCOMB'S THEORY. THUS THE PROGRAM AVOIDS THE NECESSITY OF NUMERICALLY INTEGRATING THE COMET ORBIT, AS WELL AS READING AN EXTERNAL PLANETARY EPHEMERIS. THIS PROGRAM WAS WRITTEN AT THE JET PROPULSION LABORATORY BY DR. M.S.W. KEESEY. SUBROUTINE HELXYZ WAS WRITTEN BY DR. D.K. YEOMANS. SUBROUTINE SUN WAS DEVELOPED AT THE U.S. NAVAL OBSERVATORY. THIS PROGRAM DOES NOT USE MORE THAN ONE SET OF OSCULATING ELEMENTS FOR A GIVEN EPHEMERIS INTERVAL; IE EACH EPHEMERIS INTERVAL MUST CORRESPOND TO ONE AND ONLY ONE SET OF OSCULATING ELEMENTS. INITIALIZING PARAMETERS READ IN ARE DEFINED AS FOLLOWS... From the user's terminal : 1. input file name for comet parameters eg HALLEY::16 2. output file name for predictions eg OUTPUT::14 3. prediction type - specified in prompt: option 1 gives geocentric predictions - STACOR not used option 2 gives topocentric predictions for the velocity option 3 gives topocentric predictions for azimuth/elevation input file line 1 : 'NAME' COMET NAME 80 characters maximum input file line 2 : 'NAPPS' IS THE NUMBER OF SETS OF ELEMENTS TO BE READ IN. ie the number of repeats of line 4, max = 80 sets input file line 3 : (this is read for option 1 which does not use it) 'STACOR' IS THE OBSERVATORY COORDINATES ARRAY of 3 elements : east longitude in degrees, rho*cos (geocentric latitude), rho*sin (geocentric latitude). where rho is the earth radius at the station divided by the equatorial radius of 6378160 meters. 'ETMUTC' IS THE DIFFERENCE BETWEEN EPHEMERIS TIME AND UNIVERSAL TIME COORDINATED in seconds. (supplied by IHW) input file line 4 : 'ELMTS' IS THE ARRAY OF 6 OSCULATING ELEMENTS : (from IHW) Julian date of perihelion passage (ET), perihelion distance in a.u., eccentricity, argument of perihelion (degrees), longitude of ascending node (degrees), inclination (degrees). input file line 5 : (user determined) 'NEL' IS THE KEY FOR THE LOCATION OF THE CORRECT SET OF OSCULATING ELEMENTS FOR THE CURRENT EPHEMERIS INTERVAL. 'TSTRT' IS THE BEGINNING TIME OF THE CURRENT EPHEMERIS INTERVAL, in julian days. 'TSTOP' IS THE ENDING TIME OF THE CURRENT EPHEMERIS INTERVAL, in julian days. 'H' IS THE STEP SIZE OF THE EPHEMERIS IN JULIAN DAYS. (can be fractional) AND SEVEN PARAMETERS FOR COMPUTING THE MAGNITUDE ESTIMATES. These are not necessary and the line is terminated with a / . ACEPH does not use TSTRT, TSTOP and H, as it is configured to return the the current position and velocity only. SAMPLE INPUT PARAMETER FILE FOR HARTRAO: ======================================== HALLEY'S COMET (line 1) 1 (line 2) 27.684722 0.900407079 -0.434097561 55.2 (line 3) 2446470.95542 0.5871548 0.9672617 111.84343 58.14254 162.24011 (line 4) 1 2446290.5 2446470.5 1 / (line 5) Program ACOMT ============= 256 channel comet spectral line observing program. Programs ACFIN, ACFPM, ACEPH, ALARM must be compiled and loaded. Subroutines other than fileread are in &ACSUB Spectral line source file parameters for ACOMT: line 1 (free format): --------------------- name character*20 max - source name, in quotes filename character*20 max - name of comet ephemeris parameter file, in quotes nacc integer*2 number of correlator accumulations in each position nobs integer*2 number of observations of this position pair kount integer*2 octal correlator thumbwheel count, written as @37777 for example bw real*4 correlator bandwidth in MHz eg 0.32 synofs real*4 synthesizer offset in Hz applied to center the line in the passband. If zero, the predicted radial velocity of the comet is in the center of the spectrum. synrf real*4 synthesizer offset in Hz applied to reference position ONLY, in addition to synofs, for frequency switching, and must NOT be zero. rf real*4 line rest frequency in MHz sample observing file format : ============================== 'HALLEY OH1667' 'HALLEY::16' 1 80 @17777 0.32 0.0 750.0 1667.359 Sequence of program use : ========================= 1. Run JULDA for the Julian time. 2. Set start and end Julian dates in the input file. 3. Set the calculation interval in the input file. 4. Check that the latest comet osculating elements are in the input file. 5. Run TBCEG to check the input file validity and provide predictions for the comet coordinates, radial velocity etc. 6. PRINT the output file on the Anadex. If reusing the output file note that TBCEG will overwrite the previous contents of the file, so print it between each run. 7. run RACEP to check that ACEPH reads the input file correctly. 8. Set up the observing file for ACOMT. 9. Run ACOMT using the TBCEG predictions for guidance.