Source Code
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These source-code files are part of a reconstructed copy of Comanche 45, the
second release, though not the final mission release, of the Apollo 10
Command Module (CM) Apollo Guidance Computer (AGC) software. Comanche 45 was
preceded by Comanche 44 and followed by Comanche 45/2 (the flown release). The reconstruction
is believed to be exactly accurate, but in the absence of an actual Apollo-era
listing of Comanche 45, some explanation of the reconstruction process is needed
to insure confidence in that accuracy.
The starting point was the source code of Comanche 44 (itself previously accurately
reconstructed). Comanche 44 source code was then modified
by incorporating changes known from contemporary documentation to have been
made between revisions 44 and 45. The now-reconstructed Comanche 45 source code was
verified by assembling it and checking that the assembled code had
the expected known-correct memory-bank checksums.
Note that page numbers in the reconstructed code tend to match those in the Comanche 55, the
most-similar revision of Comanche for which we have access to an actual non-reconstructed hardcopy;
the source code would likely have different page numbers in a contemporary
Comanche 45 listing.
Annotations that were not present in the contemporary source code have been added to the reconstructed
code to justify each change relative to Comanche 44. Here's a guide to the Apollo documentation referenced
in those annotations:
There is also
a detailed commentary about the reconstruction process.
Comments expected to have been present in the original source code are prefixed with a single '#' symbol,
whereas comments added later are prefixed by "##" or "###". Report any errors
noted by creating an
issue report at the Virtual AGC
Project's GitHub repository.
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019539,000002: ## Copyright: Public domain.
019540,000003: ## Filename: GROUND_TRACKING_DETERMINATION_PROGRAM_-_P21.agc
019541,000004: ## Purpose: A section of Comanche revision 045.
019542,000005: ## It is part of the reconstructed source code for the
019543,000006: ## second release of the flight software for the Command
019544,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 10.
019545,000008: ## The code has been recreated from a copy of Comanche 055. It
019546,000009: ## has been adapted such that the resulting bugger words
019547,000010: ## exactly match those specified for Comanche 45 in NASA drawing
019548,000011: ## 2021153D, which gives relatively high confidence that the
019549,000012: ## reconstruction is correct.
019550,000013: ## Assembler: yaYUL
019551,000014: ## Contact: Ron Burkey <info@sandroid.org>.
019552,000015: ## Website: www.ibiblio.org/apollo/index.html
019553,000016: ## Mod history: 2020-12-06 MAS Created from Comanche 44.
019554,000017:
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Page 456
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019556,000019: # GROUND TRACKING DETERMINATION PROGRAM P21
019557,000020:
019558,000021: # PROGRAM DESCRIPTION
019559,000022: # MOD NO - 1
019560,000023: # MOD BY - N. M. NEVILLE
019561,000024: # FUNCTIONAL DECRIPTION-
019562,000025:
019563,000026: # TO PROVIDE THE ASTRONAUT DETAILS OF THE LM OR CSM GROUND TRACK WITHOUT
019564,000027: # THE NEED FOR GROUND COMMUNICATION (REQUESTED BY DSKY).
019565,000028: # CALLING SEQUENCE-
019566,000029:
019567,000030: # ASTRONAUT REQUEST THROUGH DSKY V37E21E
019568,000031: # SUBROUTINES CALLED-
019569,000032:
019570,000033: # GOPERF4
019571,000034: # GOFLASH
019572,000035: # THISPREC
019573,000036: # OTHPREC
019574,000037: # LAT-LONG
019575,000038: # NORMAL EXIT MODES-
019576,000039:
019577,000040: # ASTRONAUT REQUEST TROUGH DSKY TO TERMINATE PROGRAM V34E
019578,000041: # ALARM OR ABORT EXIT MODES-
019579,000042:
019580,000043: # NONE
019581,000044: # OUTPUT-
019582,000045:
019583,000046: # OCTAL DISPLAY OF OPTION CODE AND VEHICLE WHOSE GROUND TRACK IS TO BE
019584,000047: # COMPUTED
019585,000048: # OPTION CODE 00002
019586,000049: # THIS 00001
019587,000050: # OTHER 00002
019588,000051: # DECIMAL DISPLAY OF TIME TO BE INTEGRATED TO HOURS , MINUTES , SECONDS
019589,000052: # DECIMAL DISPLAY OF LAT,LONG,ALT
019590,000053: # ERASABLE INITIALIZATION REQUIRED
019591,000054:
019592,000055: # AX0 2DEC 4.652459653 E-5 RADIANS %68-69 CONSTANTS"
019593,000056:
019594,000057: # -AY0 2DEC 2.147535898 E-5 RADIANS
019595,000058:
019596,000059: # AZ0 2DEC .7753206164 REVOLUTIONS
019597,000060: # FOR LUNAR ORBITS 504LM VECTOR IS NEEDED
019598,000061:
019599,000062: # 504LM 2DEC -2.700340600 E-5 RADIANS
019600,000063:
019601,000064: # 504LM _2 2DEC -7.514128400 E-4 RADIANS
019602,000065:
019603,000066: # 504LM _4 2DEC _2.553198641 E-4 RADIANS
019604,000067:
019605,000068: # NONE
019606,000069: # DEBRIS
019607,000070:
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Page 457
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019609,000072: # CENTRALS-A,Q,L
019610,000073: # OTHER-THOSE USED BY THE ABOVE LISTED SUBROUTINES
019611,000074: # SEE LEMPREC, LAT-LONG
019612,000075:
019613,000076: 33,3776 30,2000 SBANK= LOWSUPER # FOR LOW 2CADR'S.
019614,000077:
019615,000078: 33,3776 BANK 33
019616,000079: 37,2000 SETLOC P20S
019617,000080: 37,2000 BANK
019618,000081:
019619,000082: 37,2001 E4,1715 EBANK= P21TIME
019620,000083: 37,2001 COUNT 24/P21
019621,000084:
019622,000085: 37,2001 35017 PROG21 CAF ONE
019623,000086: 37,2002 55132 TS OPTION2 # ASSUMED VEHICLE IS LM, R2 = 00001
019624,000087: 37,2003 35016 CAF BIT2 # OPTION 2
019625,000088: 37,2004 04662 TC BANKCALL
019626,000089: 37,2005 21055 CADR GOPERF4
019627,000090: 37,2006 04106 TC GOTOPOOH # TERMINATE
019628,000091: 37,2007 02011 TC +2 # PROCEED VALUE OF ASSUMED VEHICLE OK
019629,000092: 37,2010 02003 TC -5 # R2 LOADED THROUGH DSKY
019630,000093: 37,2011 32151 P21PROG1 CAF V6N34 # LOAD DESIRED TIME OF LAT-LONG.
019631,000094: 37,2012 04662 TC BANKCALL
019632,000095: 37,2013 20720 CADR GOFLASH
019633,000096: 37,2014 04106 TC GOTOPOOH # TERM
019634,000097: 37,2015 02017 TC +2 # PROCEED VALUES OK
019635,000098: 37,2016 02011 TC -5 # TIME LOADED THROUGH DSKY
019636,000099: 37,2017 06006 TC INTPRET
019637,000100: 37,2020 77745 DLOAD
019638,000101: 37,2021 01046 DSPTEM1
019639,000102: 37,2022 34041 STCALL TDEC1 # INTEG TO TIME SPECIFIED IN TDEC
019640,000103: 37,2023 27442 INTSTALL
019641,000104: 37,2024 43014 BON SET
019642,000105: 37,2025 01303 P21FLAG
019643,000106: 37,2026 76044 P21CONT # ON...RECYCLE USING BASE VECTOR
019644,000107: 37,2027 01474 VINTFLAG # OFF..1ST PASS CALC BASE VECTOR
019645,000108: 37,2030 70535 SLOAD SR1
019646,000109: 37,2031 01133 OPTION2
019647,000110: 37,2032 43030 BHIZ CLEAR
019648,000111: 37,2033 76035 +2 # ZERO..THIS VEHICLE (CM)
019649,000112: 37,2034 01674 VINTFLAG # ONE...OTHER VEHICLE(LM)
019650,000113: 37,2035 43014 CLEAR CLEAR
019651,000114: 37,2036 01676 DIM0FLAG
019652,000115: 37,2037 01673 INTYPFLG # PRECISION
019653,000116: 37,2040 77624 CALL
019654,000117: 37,2041 27162 INTEGRV # CALCULATE
019655,000118: 37,2042 77650 GOTO # .AND
019656,000119: 37,2043 76065 P21VSAVE # ..SAVE BASE VECTOR
019657,000120: 37,2044 77775 P21CONT VLOAD # RECYCLE..INTEG FROM BASE VECTOR
019658,000121: 37,2045 03605 P21BASER
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Page 458
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019660,000123: 37,2046 25535 STOVL RCV # ..POS
019661,000124: 37,2047 03613 P21BASEV
019662,000125: 37,2050 15543 STODL VCV # ..VEL
019663,000126: 37,2051 02316 P21TIME
019664,000127: 37,2052 01517 STORE TET # ..TIME
019665,000128: 37,2053 43014 CLEAR CLEAR
019666,000129: 37,2054 01676 DIM0FLAG
019667,000130: 37,2055 00263 MOONFLAG
019668,000131: 37,2056 53135 SLOAD BZE
019669,000132: 37,2057 03604 P21ORIG
019670,000133: 37,2060 76063 +3 # ZERO = EARTH
019671,000134: 37,2061 77614 SET # ...2 = MOON
019672,000135: 37,2062 00063 MOONFLAG
019673,000136: 37,2063 77624 CALL
019674,000137: 37,2064 27135 INTEGRVS
019675,000138: 37,2065 77745 P21VSAVE DLOAD # SAVE CURRENT BASE VECTOR
019676,000139: 37,2066 00015 TAT
019677,000140: 37,2067 26316 STOVL P21TIME # ..TIME
019678,000141: 37,2070 00017 RATT1
019679,000142: 37,2071 27605 STOVL P21BASER # ..POS B-29 OR B-27
019680,000143: 37,2072 00025 VATT1
019681,000144: 37,2073 03613 STORE P21BASEV # ..VEL B-7 OR B-5
019682,000145: 37,2074 77646 ABVAL
019683,000146: 37,2075 27623 STOVL P21VEL # /VEL/ FOR N73 DSP
019684,000147: 37,2076 00001 RATT
019685,000148: 37,2077 50256 UNIT DOT
019686,000149: 37,2100 00007 VATT # U(R).(V)
019687,000150: 37,2101 67471 DDV ASIN # U(R).U(V)
019688,000151: 37,2102 03623 P21VEL
019689,000152: 37,2103 03625 STORE P21GAM # SIN-1 U(R).U(V), -90 TO +90
019690,000153: 37,2104 43134 SXA,2 SET
019691,000154: 37,2105 03603 P21ORIG # 0 = EARTH 2 = MOON
019692,000155: 37,2106 01063 P21FLAG
019693,000156: 37,2107 67214 P21DSP CLEAR SLOAD # GENERATE DISPLAY DATA
019694,000157: 37,2110 01663 LUNAFLAG
019695,000158: 37,2111 00050 X2
019696,000159: 37,2112 43054 BZE SET
019697,000160: 37,2113 76115 +2 # 0 = EARTH
019698,000161: 37,2114 01463 LUNAFLAG
019699,000162: 37,2115 77775 VLOAD
019700,000163: 37,2116 00001 RATT
019701,000164: 37,2117 16152 STODL ALPHAV
019702,000165: 37,2120 00015 TAT
019703,000166: 37,2121 45014 CLEAR CALL
019704,000167: 37,2122 00662 ERADFLAG
019705,000168: 37,2123 26370 LAT-LONG
019706,000169: 37,2124 77605 DMP # MPAC = ALT, METERS B-29
019707,000170: 37,2125 36153 K.01
019708,000171: 37,2126 03621 STORE P21ALT # ALT/100 FOR N73 DSP
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Page 459
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019710,000173: 37,2127 77776 EXIT
019711,000174: 37,2130 32150 CAF V06N43 # DISPLAY LAT,LONG,ALT
019712,000175: 37,2131 04662 TC BANKCALL # LAT,LONG = REVS B0 BOTH EARTH/MOON
019713,000176: 37,2132 20720 CADR GOFLASH # ALT = METERS B-29 BOTH EARTH/MOON
019714,000177: 37,2133 04106 TC GOTOPOOH # TERM
019715,000178: 37,2134 04106 TC GOTOPOOH
019716,000179: 37,2135 06006 TC INTPRET # V32E RECYCLE
019717,000180: 37,2136 43345 DLOAD DAD
019718,000181: 37,2137 02316 P21TIME
019719,000182: 37,2140 36145 600SEC # 600 SECONDS OR 10 MIN
019720,000183: 37,2141 01046 STORE DSPTEM1
019721,000184: 37,2142 77634 RTB
019722,000185: 37,2143 76011 P21PROG1
019723,000186:
019724,000187: 37,2144 00003 25140 600SEC 2DEC 60000 B-28 # 10 MIN
019725,000188:
019726,000189: 37,2146 00001 P21ONENN OCT 00001 # NEEDED TO DETERMINE VEHICLE
019727,000190: 37,2147 00000 OCT 00000 # TO BE INTEGRATED
019728,000191: 37,2150 01453 V06N43 VN 00643
019729,000192: 37,2151 01442 V6N34 VN 00634
019730,000193: 37,2152 00243 32703 K.01 2DEC .01
019731,000194:
End of include-file GROUND_TRACKING_DETERMINATION_PROGRAM_-_P21.agc. Parent file is MAIN.agc