Source Code
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These source-code files are part of a reconstructed copy of Comanche 44, the
initial release (though not the final mission release) of the Apollo 10
Command Module (CM) Apollo Guidance Computer (AGC) software. Subsequent releases
were Comanche 45 and Comanche 45/2 (the flown release on Apollo 10). The reconstruction
is believed to be exactly accurate, but in the absence of an actual Apollo-era
listing of Comanche 44, some explanation of the reconstruction process is needed
to insure confidence in that accuracy.
The starting point was the source code of Comanche 51
(separately previously reconstructed from an Apollo-era listing of Comanche 55,
flown on Apollo 11). Comanche 51 source code was then modified
by undoing changes known to have been made between revisions 44 and 51. The now-reconstructed
Comanche 44 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 printout,
although the source code would likely have different page numbers in a contemporary
Comanche 44 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 51. Here's a guide to the Apollo documentation referenced
in those annotations:
In most cases, only the titles (rather than the full texts) of PCRs are known. In addition to the
explanatory annotations, there is also
a step-by-step 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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034789,000002: ## Copyright: Public domain.
034790,000003: ## Filename: LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc
034791,000004: ## Purpose: A section of Comanche revision 044.
034792,000005: ## It is part of the reconstructed source code for the
034793,000006: ## original release of the flight software for the Command
034794,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 10.
034795,000008: ## The code has been recreated from a copy of Comanche 055. It
034796,000009: ## has been adapted such that the resulting bugger words
034797,000010: ## exactly match those specified for Comanche 44 in NASA drawing
034798,000011: ## 2021153D, which gives relatively high confidence that the
034799,000012: ## reconstruction is correct.
034800,000013: ## Assembler: yaYUL
034801,000014: ## Contact: Ron Burkey <info@sandroid.org>.
034802,000015: ## Website: www.ibiblio.org/apollo/index.html
034803,000016: ## Mod history: 2020-12-03 MAS Created from Comanche 51.
034804,000017:
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Page 785
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034806,000019: # LUNAR AND SOLAR EPHEMERIDES SUBROUTINES
034807,000020:
034808,000021: # FUNCTIONAL DESCRIPTION
034809,000022:
034810,000023: # THESE SUBROUTINES ARE USED TO DETERMINE THE POSITION AND VELOCITY
034811,000024: # VECTORS OF THE SUN AND THE MOON RELATIVE TO THE EARTH AT THE
034812,000025: # SPECIFIED GROUND ELAPSED TIME INPUT BY THE USER.
034813,000026:
034814,000027: # THE POSITION OF THE MOON IS STORED IN THE COMPUTER IN THE FORM OF
034815,000028: # A NINTH DEGREE POLYNOMIAL APPROXIMATION WHICH IS VALID OVER A 15
034816,000029: # DAY INTERVAL BEGINNING SHORTLY BEFORE LAUNCH. THEREFORE THE TIME
034817,000030: # INPUT BY THE USER SHOULD FALL WITHIN THIS 15 DAY INTERVAL.
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The 9th-degree polynomial spoken of here is a pad load, meaning
that it is not actually hardcoded into the software. Additional
information about calculating the polynomial can be found on the
Orbiter NASSP wiki, as well as information about calculation
of the
solar ephemerides.
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034825,000038:
034826,000039: # LSPOS COMPUTES THE POSITION VECTORS OF THE SUN AND THE MOON.
034827,000040:
034828,000041: # LUNPOS COMPUTES THE POSITION VECTOR OF THE MOON.
034829,000042:
034830,000043: # LUNVEL COMPUTES THE VELOCITY VECTOR OF THE MOON.
034831,000044:
034832,000045: # SOLPOS COMPUTES THE POSITION VECTOR OF THE SUN.
034833,000046:
034834,000047: # CALLING SEQUENCE
034835,000048:
034836,000049: # DLOAD CALL
034837,000050: # TIME GROUND ELAPSED TIME
034838,000051: # SUBROUTINE LSPOS OR LUNPOS OR LUNVEL OR SOLPOS
034839,000052:
034840,000053: # INPUT
034841,000054:
034842,000055: # 1) SPECIFIED GROUND ELAPSED TIME IN CS X B-28 LOADED IN MPAC.
034843,000056:
034844,000057: # 2) TIMEMO - TIME AT THE CENTER OF THE RANGE OVER WHICH THE LUNAR
034845,000058: # POSITION POLYNOMIAL IS VALID IN CS X B-42.
034846,000059:
034847,000060: # 3) VECOEM - VECTOR COEFFICIENTS OF THE LUNAR POSITION POLYNOMIAL
034848,000061: # LOADED IN DESCENDING SEQUENCE IN METERS/CS**N X B-2
034849,000062:
034850,000063: # 4) RESO - POSITION VECTOR OF THE SUN RELATIVE TO THE EARTH AT
034851,000064: # TIMEMO IN METERS X B-38.
034852,000065:
034853,000066: # 5) VESO - VELOCITY VECTOR OF THE SUN RELATIVE TO THE EARTH AT
034854,000067: # TIMEMO IN METERS/CS X B-9.
034855,000068: #
034856,000069: # 6) OMEGAES - ANGULAR VELOCITY OF THE VECTOR RESO AT TIMEMO IN
034857,000070: # REV/CS X B+26.
034858,000071:
034859,000072: # ALL EXCEPT THE FIRST INPUT ARE INCLUDED IN THE PRE-LAUNCH
034860,000073: # ERASABLE DATA LOAD.
034861,000074:
034862,000075: # OUTPUT - LSPOS
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Page 786
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034864,000077:
034865,000078: # 1) 2D OF VAC AREA CONTAINS THE POSITION VECTOR OF THE SUN RELATIVE
034866,000079: # TO THE EARTH AT TIME INPUT BY THE USER IN METERS X B-38.
034867,000080:
034868,000081: # 2) MPAC CONTAINS THE POSITION VECTOR OF THE MOON RELATIVE TO THE
034869,000082: # EARTH AT TIME INPUT BY THE USER IN METERS X B-29.
034870,000083:
034871,000084: # OUTPUT - LUNPOS
034872,000085:
034873,000086: # MPAC CONTAINS THE POSITION VECTOR OF THE MOON RELATIVE TO THE
034874,000087: # EARTH AT THE TIME INPUT BY USER IN METERS X B-29.
034875,000088:
034876,000089: # OUTPUT - LUNVEL
034877,000090:
034878,000091: # MPAC CONTAINS THE VELOCITY VECTOR OF THE MOON RELATIVE TO THE
034879,000092: # EARTH AT TIME INPUT BY THE USER IN METERS/CS X B-7.
034880,000093:
034881,000094: # OUTPUT - SOLPOS
034882,000095:
034883,000096: # MPAC CONTAINS THE POSITION VECTOR OF THE SUN RELATIVE TO THE EARTH
034884,000097: # AT TIME INPUT BY THE USER IN METERS X B-38.
034885,000098:
034886,000099: # SUBROUTINES USED
034887,000100:
034888,000101: # NONE
034889,000102:
034890,000103: # REMARKS
034891,000104:
034892,000105: # THE VAC AREA IS USED FOR STORAGE OF INTERMEDIATE AND FINAL RESULTS
034893,000106: # OF COMPUTATIONS.
034894,000107:
034895,000108: # S1, X1 AND X2 ARE USED BY THESE SUBROUTINES.
034896,000109:
034897,000110: # PRELAUNCH ERASABLE DATA LOAD ARE ONLY ERASABLE STORAGE USED BY
034898,000111: # THESE SUBROUTINES.
034899,000112:
034900,000113: # RESTARTS DURING OPERATION OF THESE SUBROUTINES MUST BE HANDLED BY
034901,000114: # THE USER.
034902,000115:
034903,000116: 36,2454 BANK 36
034904,000117: 26,2000 SETLOC EPHEM
034905,000118: 26,2000 BANK
034906,000119:
034907,000120: 26,2110 COUNT* $$/EPHEM
034908,000121: 26,2110 E7,1777 EBANK= END-E7
034909,000122: 26,2110 77774 LSPOS AXT,2 # COMPUTES POSITION VECTORS OF BOTH THE
034910,000123: 26,2111 54161 RESA # SUN AND THE MOON. THE POSITION VECTOR
034911,000124: 26,2112 52170 AXT,1 GOTO # OF THE SUN IS STORED IN 2D OF THE VAC
034912,000125: 26,2113 54143 RES # AREA. THE POSITION VECTOR OF THE MOON
034913,000126: 26,2114 54126 LSTIME # IS STORED IN MPAC.
034914,000127: 26,2115 52170 LUNPOS AXT,1 GOTO # COMPUTES THE POSITION VECTOR OF THE MOON
034915,000128: 26,2116 54162 REM # AND STORES IT IN MPAC.
034916,000129: 26,2117 54126 LSTIME
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Page 787
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034918,000131: 26,2120 52170 LUNVEL AXT,1 GOTO # COMPUTES THE VELOCITY VECTOR OF THE MOON
034919,000132: 26,2121 54173 VEM # AND STORES IT IN MPAC.
034920,000133: 26,2122 54126 LSTIME
034921,000134: 26,2123 76020 SOLPOS STQ AXT,1 # COMPUTES THE POSITION VECTOR OF THE SUN
034922,000135: 26,2124 00047 X2 # AND STORES IT IN MPAC.
034923,000136: 26,2125 54143 RES
034924,000137: 26,2126 54201 LSTIME SETPD SR
034925,000138: 26,2127 00001 0D
034926,000139: 26,2130 20617 14D
034927,000140: 26,2131 57571 TAD DCOMP
034928,000141: 26,2132 01707 TEPHEM
034929,000142: 26,2133 57571 TAD DCOMP
034930,000143: 26,2134 02034 TIMEMO
034931,000144: 26,2135 66261 SL SSP
034932,000145: 26,2136 20221 16D
034933,000146: 26,2137 00051 S1
034934,000147: 26,2140 00006 6D
034935,000148: 26,2141 77650 GOTO
034936,000149: 26,2142 00046 X1
034937,000150: 26,2143 41206 RES PUSH DMP # PD- 2
034938,000151: 26,2144 02147 OMEGAES
034939,000152: 26,2145 71406 PUSH COS # PD- 4
034940,000153: 26,2146 65361 VXSC PDDL # PD- 8
034941,000154: 26,2147 02133 RESO
034942,000155: 26,2150 63356 SIN PDVL # PD-10
034943,000156: 26,2151 02133 RESO
034944,000157: 26,2152 53406 PUSH UNIT # PD-16
034945,000158: 26,2153 53435 VXV UNIT
034946,000159: 26,2154 02141 VESO
034947,000160: 26,2155 76435 VXV VSL1 # PD-10
034948,000161: 26,2156 53361 VXSC VAD # PD-02
034949,000162: 26,2157 52172 VSL1 GOTO # RES IN METERS X B-38 IN MPAC.
034950,000163: 26,2160 00047 X2
034951,000164: 26,2161 14003 RESA STODL 2D # RES IN METERS X B-38 IN 2D OF VAC. PD- 0
034952,000165: 26,2162 63370 REM AXT,1 PDVL # PD- 2
034953,000166: 26,2163 00066 54D
034954,000167: 26,2164 02037 VECOEM
034955,000168: 26,2165 52761 REMA VXSC VAD*
034956,000169: 26,2166 00001 0D
034957,000170: 26,2167 02133 VECOEM +60D,1
034958,000171: 26,2170 72500 TIX,1 VSL2 # REM IN METERS X B-29 IN MPAC.
034959,000172: 26,2171 54165 REMA
034960,000173: 26,2172 77616 RVQ
034961,000174: 26,2173 65370 VEM AXT,1 PDDL # PD- 2
034962,000175: 26,2174 00060 48D
034963,000176: 26,2175 14214 NINEB4
034964,000177: 26,2176 74206 PUSH VXSC # PD- 4
034965,000178: 26,2177 02037 VECOEM
034966,000179: 26,2200 77761 VEMA VXSC
034967,000180: 26,2201 00001 0D
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Page 788
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034969,000182: 26,2202 14005 STODL 4D # PD- 2
034970,000183: 26,2203 41425 DSU PUSH # PD- 4
034971,000184: 26,2204 14216 ONEB4
034972,000185: 26,2205 53357 VXSC* VAD
034973,000186: 26,2206 02125 VECOEM +54D,1
034974,000187: 26,2207 00005 4D
034975,000188: 26,2210 72500 TIX,1 VSL2 # VEM IN METERS/CS X B-7 IN MPAC.
034976,000189: 26,2211 54200 VEMA
034977,000190: 26,2212 77616 RVQ
034978,000191: 26,2213 22000 00000 NINEB4 2DEC 9.0 B-4
034979,000192:
034980,000193: 26,2215 02000 00000 ONEB4 2DEC 1.0 B-4
034981,000194:
034982,000195:
034983,000196:
End of include-file LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc. Parent file is MAIN.agc