PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "GIOCALL.TXT file for GEM Data Set Collection Volume" PUBLICATION_DATE = 1995-12-31 END_OBJECT END *****File GIOCALL.TXT Mission: GIOTTO Program: Giocall.for Giocall.for is a fortran program designed to call the subroutine giodat.for to access data from the Giotto mission state vector file POSITION, and return this data in barycentric 'xyz' state vector coordinates, for a given time in TUTC 1950 EME standard. Giocall.for also calculates the heliocentric and geocentric coordinates, and the distance from Giotto to the target comet from the barycentric state vectors, or calculates the time at which Giotto was a given distance from COMET, and can return these data as well. The data file POSITION.TXT can be found in the 'ephemris' directory on the GEM CDROM disk. POSITION.TXT must be copied from the CDROM to a file named POSITION (case sensitive with no file extension). POSITION must be in the same directory as giocall (the executable module), otherwise giodat will be unable to find it and will quit without executing. To use Giocall.for it must first be compiled. Giocall has been compiled and run under unix and MS-DOS version 6.2 systems. It is not known how giocall works on other systems. Separate instructions for compilation under unix and dos are provided, followed by generic instructions for running giocall under unix and dos. UNIX COMPILE INSTRUCTIONS: On most unix systems at the prompt ( '>' ) type: > f77 giocall.for -o giocall or use whatever fortran compiler is available and set the compiled output executable to be called "giocall". DOS COMPILE INSTRUCTIONS: On dos systems, giocall.for requires a few code changes before it will compile under dos. Using an available editor, find all occurrences of the characters 'DOS CHANGES' and make the specified changes. Note that these changes were required by the compiler: MS-FORTRAN version 5.0 for MS-DOS. It is not known if other dos-fortran compilers require additional code changes. When the code changes are completed, at the dos prompt ('>') type: > fl travcall.for to compile giocall.for. The compiled output executable will be called "giocall". RUN INSTRUCTIONS: Note that for dos systems, when prompted for character input such as 'p' the single quotes MUST BE TYPED; when a series of character input is required such as 'y,y,y,y' single quotes must be typed around each character in the series (type 'y','y','y','y'). For unix systems, do not type quotes around character input. For unix and dos systems, when prompted for numeric input such as '15531.5' do not type the quotes. To run giocall under unix or dos type: > giocall this should bring up a message like this: OPTIONS: ENTER t TO FIND THE TIME FOR GIVEN DISTANCE, OR p TO FIND THE POSITION OF COMET/GIOTTO AT A GIVEN TIME. if 'p' is entered then this message will appear: BARYCENTRIC, HELIOCENTRIC, GEOCENTRIC, AND/OR COMETOCENTRIC COORDINATES? (y/n,y/n,y/n,y/n) all four, some, or none of these options may be chosen. For this example 'y,y,y,y' will be entered. The next message will be: ENTER SIGNAL RECEPTION TIME(-999 T0 QUIT) for this example, '15531.5' will be entered as the reception time to be checked. The following will then be returned as the data from POSITION for TUTC 15531.5: BARYCENTRIC GIOTTO POSITION (X,Y,Z) -142252382.93239 KM -36687057.981389 KM -31578313.686062 KM BARYCENTRIC GIOTTO VELOCITY (Vx,Vy,Vz) 10.718468932759 KM/S -26.552031389121 KM/S -10.879782118639 KM/S BARYCENTRIC COMET POSITION (X,Y,Z) -142286508.97860 KM -36577855.098070 KM -31699713.014798 KM BARYCENTRIC COMET VELOCITY (Vx,Vy,Vz) 13.581512699007 KM/S -35.710152225478 KM/S -0.69754796172356 KM/S BARYCENTRIC EARTH POSITION (X,Y,Z) 47048129.833805 KM -132326119.72313 KM -57386562.721319 KM BARYCENTRIC EARTH VELOCITY (Vx,Vy,Vz) 27.853848960738 KM/S 8.3079819175546 KM/S 3.6008191823448 KM/S HELIOCENTRIC GIOTTO POSITION (X,Y,Z) -142618677.85712 KM -37157426.865180 KM -31769081.664188 KM HELIOCENTRIC GIOTTO VELOCITY (Vx,Vy,Vz) 10.718400359659 KM/S -26.560872405258 KM/S -10.883630137677 KM/S HELIOCENTRIC COMET POSITION (X,Y,Z) -142652803.90333 KM -37048223.981861 KM -31890480.992924 KM HELIOCENTRIC COMET VELOCITY (Vx,Vy,Vz) 13.581444125907 KM/S -35.718993241616 KM/S -0.70139598076157 KM/S HELIOCENTRIC EARTH POSITION (X,Y,Z) 46681834.909076 KM -132796488.60693 KM -57577330.699445 KM HELIOCENTRIC EARTH VELOCITY (Vx,Vy,Vz) 27.853780387638 KM/S 8.2991409014174 KM/S 3.5969711633068 KM/S GEOCENTRIC GIOTTO POSITION (X,Y,Z) -189300512.76620 KM 95639061.741746 KM 25808249.035257 KM GEOCENTRIC GIOTTO VELOCITY (Vx,Vy,Vz) -17.135380027979 KM/S -34.860013306676 KM/S -14.480601300984 KM/S GEOCENTRIC COMET POSITION (X,Y,Z) -189334638.81240 KM 95748264.625065 KM 25686849.706521 KM GEOCENTRIC COMET VELOCITY (Vx,Vy,Vz) -14.272336261731 KM/S -44.018134143033 KM/S -4.2983671440684 KM/S COMETOCENTRIC GIOTTO POSITION (X,Y,Z) 34126.046203554 KM -109202.88331917 KM 121399.32873559 KM COMETOCENTRIC GIOTTO VELOCITY(Vx,Vy,Vz) -2.8630437662487 KM/S 9.1581208363573 KM/S -10.1822341569159 KM/S DISTANCE FROM GIOTTO TO COMET 166816.22754444 KM note that "DISTANCE FROM GIOTTO TO COMET" is always printed out, even if 'n,n,n,n' had been chosen for coordinate choices. This will be followed by: ENTER SIGNAL RECEPTION TIME(-999 T0 QUIT) which starts the search again. If '-999' is entered: SEARCH FOR ANOTHER TIME OR POSITION?(t/p/q) entering 'q' will end the program, 'p' will start over with the choice of coordinate system, and 't' will bring up this message: AT TIME OF CLOSEST APPROACH 15531.638004482 DAYS EME50 GIOTTO WAS 14.673154565233 KM FROM COMET note that giocall always gives the time and distance of closest approach the first time it is asked to find a time for a given position. ENTER a IF GIOTTOIS APPROACHING COMET, r IF RECEDING for this example, 'a' is chosen, then: ENTER DISTANCE FROM GIOTTO TO COMET IN KM again for this example, '166816.22754444' is chosen to test the accuracy of the iterative 'time' search using the result of the previous search, with these results: AT TUTC 15531.500000000, GIOTTO WAS 166816.22753564 KM FROM' COMET at this point the message: SEARCH FOR ANOTHER TIME OR POSITION?(t/p/q) will reappear. To exit the program, enter 'q'.