Source Code

These source-code files were derived from scans of the Colossus 237 (Apollo 8 Command Module) program listing from the private collection of original AGC developer Fred Martin. Scanning was by Ron Burkey. Pre-existing Colossus 249 (Apollo 9 CM) source files were used as a template, and changes between Colossus 249 and Colossus 237 were manually transcribed by a team of volunteers. Note that the page images presented online are of reduced quality, and that additional images are available. Report any conversion errors or legibility problems in page images to info@sandroid.org. Notations on the program listing read, in part:

	GAP: ASSEMBLE REVISION 237 OF AGC PROGRAM COLOSSUS 
	BY NASA 2021111-031  1:17 AUG. 24, 1968
Note that the date is the date of the printout, not the date of the program revision.

019592,000002:                                                                                                  ## Copyright:   Public domain.
019593,000003:                                                                                                  ## Filename:    GROUND_TRACKING_DETERMINATION_PROGRAM_-_P21.agc
019594,000004:                                                                                                  ## Purpose:     Part of the source code for Colossus build 237.
019595,000005:                                                                                                  ##              This is for the Command Module's (CM) Apollo Guidance
019596,000006:                                                                                                  ##              Computer (AGC), for Apollo 8.
019597,000007:                                                                                                  ## Assembler:   yaYUL
019598,000008:                                                                                                  ## Contact:     Jim Lawton <jim DOT lawton AT gmail DOT com>
019599,000009:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
019600,000010:                                                                                                  ## Page Scans:  www.ibiblio.org/apollo/ScansForConversion/Colossus237/
019601,000011:                                                                                                  ## Mod history: 2011-02-02 JL   Adapted from corresponding Colossus 249 file.
019602,000012:                                                                                                  ##              2016-12-31 RSB  Proofed comment text using octopus/ProoferComments,
019603,000013:                                                                                                  ##                              and corrected errors found.
019604,000014:                                                                                                  ##              2017-01-14 RSB  Corrected comment-errors located in diff'ing
019605,000015:                                                                                                  ##                              vs Colossus 249
019606,000016: 

Page 447

019608,000018:                                                                                                  #  GROUND TRACKING DETERMINATION PROGRAM P21
019609,000019:                                                                                                  #  PROGRAM DESCRIPTION
019610,000020:                                                                                                  #  MOD NO - 1
019611,000021:                                                                                                  #  MOD BY - N.M.NEVILLE
019612,000022:                                                                                                  #  FUNCTIONAL DECRIPTION-
019613,000023: 
019614,000024:                                                                                                  #  TO PROVIDE THE ASTRONAUT DETAILS OF THE LM OR CSM GROUND TRACK WITHOUT
019615,000025:                                                                                                  #  THE NEED FOR GROUND COMMUNICATION (REQUESTED BY DSKY).
019616,000026:                                                                                                  #  CALLING SEQUENCE-
019617,000027: 
019618,000028:                                                                                                  #  ASTRONAUT REQUEST THROUGH DSKY V37E21E
019619,000029:                                                                                                  #  SUBROUTINES CALLED-
019620,000030: 
019621,000031:                                                                                                  #  GOPERF4
019622,000032:                                                                                                  #  GOFLASH
019623,000033:                                                                                                  #  THISPREC
019624,000034:                                                                                                  #  OTHPREC
019625,000035:                                                                                                  #  LAT-LONG
019626,000036:                                                                                                  #  NORMAL EXIT MODES-
019627,000037: 
019628,000038:                                                                                                  #  ASTRONAUT REQUEST TROUGH DSKY TO TERMINATE PROGRAM V34E
019629,000039:                                                                                                  #  ALARM OR ABORT EXIT MODES-
019630,000040: 
019631,000041:                                                                                                  #  NONE
019632,000042:                                                                                                  #  OUTPUT-
019633,000043: 
019634,000044:                                                                                                  #  OCTAL DISPLAY OF OPTION CODE AND VEHICLE WHOSE GROUND TRACK IS TO BE
019635,000045:                                                                                                  #  COMPUTED
019636,000046:                                                                                                  #           OPTION CODE  00002
019637,000047:                                                                                                  #           THIS         00001
019638,000048:                                                                                                  #           OTHER        00002
019639,000049:                                                                                                  #  DECIMAL DISPLAY OF TIME TO BE INTEGRATED TO HOURS , MINUTES , SECONDS
019640,000050:                                                                                                  #  DECIMAL DISPLAY OF LAT,LONG,ALT
019641,000051:                                                                                                  #  ERASABLE INITIALIZATION REQUIRED
019642,000052: 
019643,000053:                                                                                                  #  AX0      2DEC   4.652459653 E-5   RADIANS       %68-69 CONSTANTS"
019644,000054: 
019645,000055:                                                                                                  #  -AY0     2DEC   2.147535898 E-5   RADIANS
019646,000056: 
019647,000057:                                                                                                  #  AZ0      2DEC   .7753206164       REVOLUTIONS
019648,000058:                                                                                                  #  FOR LUNAR ORBITS 504LM VECTOR IS NEEDED
019649,000059: 
019650,000060:                                                                                                  #  504LM    2DEC   -2.700340600 E-5  RADIANS
019651,000061: 
019652,000062:                                                                                                  #  504LM _2 2DEC   -7.514128400 E-4  RADIANS
019653,000063: 
019654,000064:                                                                                                  #  504LM _4 2DEC   _2.553198641 E-4  RADIANS
019655,000065: 
019656,000066:                                                                                                  #        NONE
019657,000067:                                                                                                  #  DEBRIS

Page 448

019659,000069: 
019660,000070:                                                                                                  #  CENTRALS-A,Q,L
019661,000071:                                                                                                  #  OTHER-THOSE USED BY THE ABOVE LISTED SUBROUTINES
019662,000072:                                                                                                  #  SEE LEMPREC,LAT-LONG
019663,000073: 33,3773  30,2000                                  SBANK=   LOWSUPER                              #  FOR LOW 2CADR'S.
019664,000074: 
019665,000075: 33,3773                                           BANK     33                                    
019666,000076: 37,2000                                           SETLOC   P20S                                  
019667,000077: 37,2000                                           BANK                                           
019668,000078: 
019669,000079: 37,2001  E4,1715                                  EBANK=   P21TIME                               
019670,000080: 37,2001                                           COUNT    24/P21                                
019671,000081: 
019672,000082: 37,2001           34712        PROG21             CAF      ONE                                   
019673,000083: 37,2002           55132                           TS       OPTION2                               #  ASSUMED VEHICLE IS LM , R2 = 00001
019674,000084: 37,2003           34711                           CAF      BIT2                                  #   OPTION 2
019675,000085: 37,2004           04555                           TC       BANKCALL                              
019676,000086: 37,2005           20761                           CADR     GOPERF4                               
019677,000087: 37,2006           04106                           TC       GOTOPOOH                              #  TERMINATE
019678,000088: 37,2007           02011                           TC       +2                                    #  PROCEED VALUE OF ASSUMED VEHICLE OK
019679,000089: 37,2010           02003                           TC       -5                                    #  R2 LOADED THROUGH DSKY
019680,000090: 37,2011           32102        P21PROG1           CAF      V6N34                                 #  LOAD DESIRED TIME OF LAT-LONG.
019681,000091: 37,2012           04555                           TC       BANKCALL                              
019682,000092: 37,2013           20624                           CADR     GOFLASH                               
019683,000093: 37,2014           04106                           TC       GOTOPOOH                              #  TERM
019684,000094: 37,2015           02017                           TC       +2                                    #  PROCEED VALUES OK
019685,000095: 37,2016           02011                           TC       -5                                    #  TIME LOADED THROUGH DSKY
019686,000096: 37,2017           06006                           TC       INTPRET                               
019687,000097: 37,2020           77745                           DLOAD                                          
019688,000098: 37,2021           01046                                    DSPTEM1                               
019689,000099: 37,2022           02316                           STORE    P21TIME                               
019690,000100: 37,2023           45335                           SLOAD    DSU                                   
019691,000101: 37,2024           01133                                    OPTION2                               
019692,000102: 37,2025           36100                                    P21ONENN                              
019693,000103: 37,2026           71230                           BHIZ     DLOAD                                 
019694,000104: 37,2027           76042                                    P21PROG2                              #  VEHICLE TO BE INTEGRATED IS LEM
019695,000105: 37,2030           02316                                    P21TIME                               #  VEHICLE TO BE INTEGRATED IS CSM
019696,000106: 37,2031           34041                           STCALL   TDEC1                                 #  INTEGRATE TO TIME SPECIFIED IN TDEC
019697,000107: 37,2032           27036                                    OTHPREC                               #  ADJUST UNITS FOR LAT-LONG ROUTINE
019698,000108: 37,2033           46135        P21PROGA           SLOAD    BHIZ                                  
019699,000109: 37,2034           00050                                    X2                                    
019700,000110: 37,2035           76050                                    P21PROG3                              
019701,000111: 37,2036           43175                           VLOAD    SETGO                                 
019702,000112: 37,2037           00001                                    RATT                                  
019703,000113: 37,2040           01423                                    LUNAFLAG                              
019704,000114: 37,2041           76053                                    P21PROG4                              
019705,000115: 37,2042           77745        P21PROG2           DLOAD                                          
019706,000116: 37,2043           02316                                    P21TIME                               
019707,000117: 37,2044           34041                           STCALL   TDEC1                                 
019708,000118: 37,2045           27022                                    THISPREC                              

Page 449

019710,000120: 37,2046           77650                           GOTO                                           
019711,000121: 37,2047           76033                                    P21PROGA                              
019712,000122: 37,2050           43175        P21PROG3           VLOAD    CLEAR                                 
019713,000123: 37,2051           00001                                    RATT                                  
019714,000124: 37,2052           01663                                    LUNAFLAG                              
019715,000125: 37,2053           16152        P21PROG4           STODL    ALPHAV                                
019716,000126: 37,2054           00015                                    TAT                                   
019717,000127: 37,2055           45014                           CLEAR    CALL                                  
019718,000128: 37,2056           00662                                    ERADFLAG                              
019719,000129: 37,2057           26322                                    LAT-LONG                              
019720,000130: 37,2060           77776                           EXIT                                           
019721,000131: 37,2061           32101                           CAF      V06N43                                #  DISPLAY LAT,LONG,ALT
019722,000132: 37,2062           04555                           TC       BANKCALL                              #  LAT,LONG = 1/2 REVS B0
019723,000133: 37,2063           20624                           CADR     GOFLASH                               #  ALT = KM  B14
019724,000134: 37,2064           04106                           TC       GOTOPOOH                              #  TERM
019725,000135: 37,2065           04106                           TC       GOTOPOOH                              
019726,000136: 37,2066           06006                           TC       INTPRET                               #  V32E RECYCLE
019727,000137: 37,2067           43345                           DLOAD    DAD                                   
019728,000138: 37,2070           02316                                    P21TIME                               
019729,000139: 37,2071           36076                                    600SEC                                #  600 SECONDS OR 10 MIN
019730,000140: 37,2072           01046                           STORE    DSPTEM1                               
019731,000141: 37,2073           77634                           RTB                                            
019732,000142: 37,2074           76011                                    P21PROG1                              
019733,000143: 
019734,000144: 37,2075           00003 25140  600SEC             2DEC     60000      B-28                       #  10 MIN
019735,000145: 37,2077           00001        P21ONENN           OCT      00001                                 #  NEEDED TO DETERMINE VEHICLE
019736,000146: 37,2100           00000                           OCT      00000                                 #  TO BE INTEGRATED
019737,000147: 37,2101           01453        V06N43             VN       00643                                 
019738,000148: 37,2102           01442        V6N34              VN       00634                                 

End of include-file GROUND_TRACKING_DETERMINATION_PROGRAM_-_P21.agc.  Parent file is MAIN.agc