Source Code
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These source-code files are part of a reconstructed copy of Comanche 51, the
initial release (though not the final mission release) of the Apollo 11
Command Module (CM) Apollo Guidance Computer (AGC) software. The flown, final
release was Comanche 55. The reconstruction is believed to be exactly accurate,
but in the absence of an actual Apollo-era listing of Comanche 51, some
explanation of the reconstruction process is needed to insure confidence in
that accuracy.
The starting point was the source code of Comanche 55, whose original source code
is available. Comanche 55 source code was then modified by undoing changes known
to have been made between revisions 51 and 55. The most-significant steps involved
reverting changes related to the R-2 lunar potential model, the details of which
were known from the previous, separate, independent reconstruction of the Apollo 10
Lunar Module software Luminary 69/2. The now-reconstructed
Comanche 51 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 match those on the Comanche 55 or Luminary 69 printouts, although
the source code would likely have different page numbers in a contemporary Comanche 51 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 55. Here's a guide
to some of the Apollo documentation relevant to those annotations:
Among documentation not actually referenced in the annotations, there is
a short writeup about the reconstruction process in our software repository
that may be helpful in understanding it from a different perspective. There's also
a handy table
that lists what the number of memory-words should be for each routine in Comanche 51,
which could make a nice double-check; however, we've not performed that double-check ourselves.
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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019561,000002: ## Copyright: Public domain.
019562,000003: ## Filename: GROUND_TRACKING_DETERMINATION_PROGRAM_-_P21.agc
019563,000004: ## Purpose: A section of Comanche revision 051.
019564,000005: ## It is part of the reconstructed source code for the
019565,000006: ## original release of the flight software for the Command
019566,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
019567,000008: ## The code has been recreated from a copy of Comanche 055. It
019568,000009: ## has been adapted such that the resulting bugger words
019569,000010: ## exactly match those specified for Comanche 51 in NASA drawing
019570,000011: ## 2021153D, which gives relatively high confidence that the
019571,000012: ## reconstruction is correct.
019572,000013: ## Reference: pp. 456-459
019573,000014: ## Assembler: yaYUL
019574,000015: ## Contact: Ron Burkey <info@sandroid.org>.
019575,000016: ## Website: www.ibiblio.org/apollo/index.html
019576,000017: ## Mod history: 2019-07-30 MAS Created from Comanche 55.
019577,000018:
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Page 456
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019579,000020: # GROUND TRACKING DETERMINATION PROGRAM P21
019580,000021:
019581,000022: # PROGRAM DESCRIPTION
019582,000023: # MOD NO - 1
019583,000024: # MOD BY - N. M. NEVILLE
019584,000025: # FUNCTIONAL DECRIPTION-
019585,000026:
019586,000027: # TO PROVIDE THE ASTRONAUT DETAILS OF THE LM OR CSM GROUND TRACK WITHOUT
019587,000028: # THE NEED FOR GROUND COMMUNICATION (REQUESTED BY DSKY).
019588,000029: # CALLING SEQUENCE-
019589,000030:
019590,000031: # ASTRONAUT REQUEST THROUGH DSKY V37E21E
019591,000032: # SUBROUTINES CALLED-
019592,000033:
019593,000034: # GOPERF4
019594,000035: # GOFLASH
019595,000036: # THISPREC
019596,000037: # OTHPREC
019597,000038: # LAT-LONG
019598,000039: # NORMAL EXIT MODES-
019599,000040:
019600,000041: # ASTRONAUT REQUEST TROUGH DSKY TO TERMINATE PROGRAM V34E
019601,000042: # ALARM OR ABORT EXIT MODES-
019602,000043:
019603,000044: # NONE
019604,000045: # OUTPUT-
019605,000046:
019606,000047: # OCTAL DISPLAY OF OPTION CODE AND VEHICLE WHOSE GROUND TRACK IS TO BE
019607,000048: # COMPUTED
019608,000049: # OPTION CODE 00002
019609,000050: # THIS 00001
019610,000051: # OTHER 00002
019611,000052: # DECIMAL DISPLAY OF TIME TO BE INTEGRATED TO HOURS , MINUTES , SECONDS
019612,000053: # DECIMAL DISPLAY OF LAT,LONG,ALT
019613,000054: # ERASABLE INITIALIZATION REQUIRED
019614,000055:
019615,000056: # AX0 2DEC 4.652459653 E-5 RADIANS %68-69 CONSTANTS"
019616,000057:
019617,000058: # -AY0 2DEC 2.147535898 E-5 RADIANS
019618,000059:
019619,000060: # AZ0 2DEC .7753206164 REVOLUTIONS
019620,000061: # FOR LUNAR ORBITS 504LM VECTOR IS NEEDED
019621,000062:
019622,000063: # 504LM 2DEC -2.700340600 E-5 RADIANS
019623,000064:
019624,000065: # 504LM _2 2DEC -7.514128400 E-4 RADIANS
019625,000066:
019626,000067: # 504LM _4 2DEC _2.553198641 E-4 RADIANS
019627,000068:
019628,000069: # NONE
019629,000070: # DEBRIS
019630,000071:
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Page 457
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019632,000073: # CENTRALS-A,Q,L
019633,000074: # OTHER-THOSE USED BY THE ABOVE LISTED SUBROUTINES
019634,000075: # SEE LEMPREC, LAT-LONG
019635,000076:
019636,000077: 33,3776 30,2000 SBANK= LOWSUPER # FOR LOW 2CADR'S.
019637,000078:
019638,000079: 33,3776 BANK 33
019639,000080: 37,2000 SETLOC P20S
019640,000081: 37,2000 BANK
019641,000082:
019642,000083: 37,2001 E4,1715 EBANK= P21TIME
019643,000084: 37,2001 COUNT 24/P21
019644,000085:
019645,000086: 37,2001 35017 PROG21 CAF ONE
019646,000087: 37,2002 55132 TS OPTION2 # ASSUMED VEHICLE IS LM, R2 = 00001
019647,000088: 37,2003 35016 CAF BIT2 # OPTION 2
019648,000089: 37,2004 04662 TC BANKCALL
019649,000090: 37,2005 21055 CADR GOPERF4
019650,000091: 37,2006 04106 TC GOTOPOOH # TERMINATE
019651,000092: 37,2007 02011 TC +2 # PROCEED VALUE OF ASSUMED VEHICLE OK
019652,000093: 37,2010 02003 TC -5 # R2 LOADED THROUGH DSKY
019653,000094: 37,2011 32152 P21PROG1 CAF V6N34 # LOAD DESIRED TIME OF LAT-LONG.
019654,000095: 37,2012 04662 TC BANKCALL
019655,000096: 37,2013 20720 CADR GOFLASH
019656,000097: 37,2014 04106 TC GOTOPOOH # TERM
019657,000098: 37,2015 02017 TC +2 # PROCEED VALUES OK
019658,000099: 37,2016 02011 TC -5 # TIME LOADED THROUGH DSKY
019659,000100: 37,2017 06006 TC INTPRET
019660,000101: 37,2020 77745 DLOAD
019661,000102: 37,2021 01046 DSPTEM1
019662,000103: 37,2022 34041 STCALL TDEC1 # INTEG TO TIME SPECIFIED IN TDEC
019663,000104: 37,2023 27442 INTSTALL
019664,000105: 37,2024 43014 BON SET
019665,000106: 37,2025 01303 P21FLAG
019666,000107: 37,2026 76044 P21CONT # ON...RECYCLE USING BASE VECTOR
019667,000108: 37,2027 01474 VINTFLAG # OFF..1ST PASS CALC BASE VECTOR
019668,000109: 37,2030 70535 SLOAD SR1
019669,000110: 37,2031 01133 OPTION2
019670,000111: 37,2032 43030 BHIZ CLEAR
019671,000112: 37,2033 76035 +2 # ZERO..THIS VEHICLE (CM)
019672,000113: 37,2034 01674 VINTFLAG # ONE...OTHER VEHICLE(LM)
019673,000114: 37,2035 43014 CLEAR CLEAR
019674,000115: 37,2036 01676 DIM0FLAG
019675,000116: 37,2037 01673 INTYPFLG # PRECISION
019676,000117: 37,2040 77624 CALL
019677,000118: 37,2041 27162 INTEGRV # CALCULATE
019678,000119: 37,2042 77650 GOTO # .AND
019679,000120: 37,2043 76065 P21VSAVE # ..SAVE BASE VECTOR
019680,000121: 37,2044 77775 P21CONT VLOAD # RECYCLE..INTEG FROM BASE VECTOR
019681,000122: 37,2045 03605 P21BASER
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019683,000124: 37,2046 25535 STOVL RCV # ..POS
019684,000125: 37,2047 03613 P21BASEV
019685,000126: 37,2050 15543 STODL VCV # ..VEL
019686,000127: 37,2051 02316 P21TIME
019687,000128: 37,2052 01517 STORE TET # ..TIME
019688,000129: 37,2053 43014 CLEAR CLEAR
019689,000130: 37,2054 01676 DIM0FLAG
019690,000131: 37,2055 00263 MOONFLAG
019691,000132: 37,2056 53135 SLOAD BZE
019692,000133: 37,2057 03604 P21ORIG
019693,000134: 37,2060 76063 +3 # ZERO = EARTH
019694,000135: 37,2061 77614 SET # ...2 = MOON
019695,000136: 37,2062 00063 MOONFLAG
019696,000137: 37,2063 77624 CALL
019697,000138: 37,2064 27135 INTEGRVS
019698,000139: 37,2065 77745 P21VSAVE DLOAD # SAVE CURRENT BASE VECTOR
019699,000140: 37,2066 00015 TAT
019700,000141: 37,2067 26316 STOVL P21TIME # ..TIME
019701,000142: 37,2070 00017 RATT1
019702,000143: 37,2071 27605 STOVL P21BASER # ..POS B-29 OR B-27
019703,000144: 37,2072 00025 VATT1
019704,000145: 37,2073 03613 STORE P21BASEV # ..VEL B-7 OR B-5
019705,000146: 37,2074 53646 ABVAL SL*
019706,000147: 37,2075 57576 0,2
019707,000148: 37,2076 27623 STOVL P21VEL # /VEL/ FOR N73 DSP
019708,000149: 37,2077 00001 RATT
019709,000150: 37,2100 50256 UNIT DOT
019710,000151: 37,2101 00007 VATT # U(R).(V)
019711,000152: 37,2102 67471 DDV ASIN # U(R).U(V)
019712,000153: 37,2103 03623 P21VEL
019713,000154: 37,2104 03625 STORE P21GAM # SIN-1 U(R).U(V), -90 TO +90
019714,000155: 37,2105 43134 SXA,2 SET
019715,000156: 37,2106 03603 P21ORIG # 0 = EARTH 2 = MOON
019716,000157: 37,2107 01063 P21FLAG
019717,000158: 37,2110 67214 P21DSP CLEAR SLOAD # GENERATE DISPLAY DATA
019718,000159: 37,2111 01663 LUNAFLAG
019719,000160: 37,2112 00050 X2
019720,000161: 37,2113 43054 BZE SET
019721,000162: 37,2114 76116 +2 # 0 = EARTH
019722,000163: 37,2115 01463 LUNAFLAG
019723,000164: 37,2116 77775 VLOAD
019724,000165: 37,2117 00001 RATT
019725,000166: 37,2120 16152 STODL ALPHAV
019726,000167: 37,2121 00015 TAT
019727,000168: 37,2122 45014 CLEAR CALL
019728,000169: 37,2123 00662 ERADFLAG
019729,000170: 37,2124 26370 LAT-LONG
019730,000171: 37,2125 77605 DMP # MPAC = ALT, METERS B-29
019731,000172: 37,2126 36154 K.01
019732,000173: 37,2127 03621 STORE P21ALT # ALT/100 FOR N73 DSP
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019734,000175: 37,2130 77776 EXIT
019735,000176: 37,2131 32151 CAF V06N43 # DISPLAY LAT,LONG,ALT
019736,000177: 37,2132 04662 TC BANKCALL # LAT,LONG = REVS B0 BOTH EARTH/MOON
019737,000178: 37,2133 20720 CADR GOFLASH # ALT = METERS B-29 BOTH EARTH/MOON
019738,000179: 37,2134 04106 TC GOTOPOOH # TERM
019739,000180: 37,2135 04106 TC GOTOPOOH
019740,000181: 37,2136 06006 TC INTPRET # V32E RECYCLE
019741,000182: 37,2137 43345 DLOAD DAD
019742,000183: 37,2140 02316 P21TIME
019743,000184: 37,2141 36146 600SEC # 600 SECONDS OR 10 MIN
019744,000185: 37,2142 01046 STORE DSPTEM1
019745,000186: 37,2143 77634 RTB
019746,000187: 37,2144 76011 P21PROG1
019747,000188:
019748,000189: 37,2145 00003 25140 600SEC 2DEC 60000 B-28 # 10 MIN
019749,000190:
019750,000191: 37,2147 00001 P21ONENN OCT 00001 # NEEDED TO DETERMINE VEHICLE
019751,000192: 37,2150 00000 OCT 00000 # TO BE INTEGRATED
019752,000193: 37,2151 01453 V06N43 VN 00643
019753,000194: 37,2152 01442 V6N34 VN 00634
019754,000195: 37,2153 00243 32703 K.01 2DEC .01
019755,000196:
End of include-file GROUND_TRACKING_DETERMINATION_PROGRAM_-_P21.agc. Parent file is MAIN.agc