Source Code
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These source-code files are part of a reconstructed copy of Luminary 69/2,
the flown, final release of the Apollo 10 Lunar Module (LM) Apollo Guidance Computer (AGC) software.
The reconstruction is based on the source code of Luminary 69 — i.e., the
initial, unflown version, "revision 0" — of which
a contemporary listing was available. The code was then updated by incorporating the
differences between Luminary 69 and Luminary 69/2, known from other contemporary
documentation. The only such difference is the implementation in
Luminary 69/2 of the "R-2 Lunar Potential Model", the source code for which was taken
from program Luminary 99/1 (Apollo 11 LM), of which a contemporary listing was also available.
Finally, the now-reconstructed Luminary 69/2 was then validated by assembling it to
executable form and verifying that its memory banks had the correct checksums,
known from still other contemporary documentation.
Note that page numbers in the reconstructed code match those in the original Luminary 69
program listing, or in the ORBITAL INTEGRATION log section, in Luminary 99/1. Page numbers
would certainly differ somewhat in a contemporary Luminary 69/2 listing.
Moreover, annotations that were not present in the contemporary source code have been added
to the reconstructed code to justify each change in Luminary 69/2 relative to
Luminary 69. Here's a guide to the Apollo documentation referenced in those annotations:
Comments from 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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014493,000002: ## Copyright: Public domain.
014494,000003: ## Filename: LEM_GEOMETRY.agc
014495,000004: ## Purpose: A section of LUM69 revision 2.
014496,000005: ## It is part of the reconstructed source code for the flown
014497,000006: ## version of the flight software for the Lunar Module's (LM)
014498,000007: ## Apollo Guidance Computer (AGC) for Apollo 10. The code has
014499,000008: ## been recreated from a copy of Luminary revsion 069, using
014500,000009: ## changes present in Luminary 099 which were described in
014501,000010: ## Luminary memos 75 and 78. The code has been adapted such
014502,000011: ## that the resulting bugger words exactly match those specified
014503,000012: ## for LUM69 revision 2 in NASA drawing 2021152B, which gives
014504,000013: ## relatively high confidence that the reconstruction is correct.
014505,000014: ## Reference: pp. 334-338
014506,000015: ## Assembler: yaYUL
014507,000016: ## Contact: Ron Burkey <info@sandroid.org>.
014508,000017: ## Website: www.ibiblio.org/apollo/index.html
014509,000018: ## Mod history: 2019-07-27 MAS Created from Luminary 69.
014510,000019: ## 2021-05-30 ABS Replaced use of ANTENBIT with BIT12 to match
014511,000020: ## Luminary 69.
014512,000021:
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Page 334
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014514,000023: 23,2041 BANK 23
014515,000024: 13,2000 SETLOC LEMGEOM
014516,000025: 13,2000 BANK
014517,000026:
014518,000027: 13,2070 30,2000 SBANK= LOWSUPER
014519,000028: 13,2070 E5,1642 EBANK= XSM
014520,000029:
014521,000030: # THESE TWO ROUTINES COMPUTE THE ACTUAL STATE VECTOR FOR LM,CSM BY ADDING
014522,000031: # THE CONIC R,V AND THE DEVIATIONSR,V. THE STATE VECTORS ARE CONVERTED TO
014523,000032: # METERS B-29 AND METERS/CSEC B-7 AND STORED APPROPRIATELY IN RN,VN OR
014524,000033: # R-OTHER , V-OTHER FOR DOWNLINK. THE ROUTINES NAMES ARE SWITCHED IN THE
014525,000034: # OTHER VEHICLES COMPUTER.
014526,000035:
014527,000036: # INPUT
014528,000037: # STATE VECTOR IN TEMPORARY STORAGE AREA
014529,000038: # IF STATE VECTOR IS SCALED POS B27 AND VEL B5
014530,000039: # SET X2 TO +2
014531,000040: # IF STATE VECTOR IS SCALED POS B29 AND VEL B7
014532,000041: # SET X2 TO 0
014533,000042:
014534,000043: # OUTPUT
014535,000044: # R(T) IN RN, V(T) IN VN, T IN PIPTIME
014536,000045: # OR
014537,000046: # R(T) IN R-OTHER, V(T) IN V-OTHER (T IS DEFINED BY T-OTHER)
014538,000047:
014539,000048: 13,2070 COUNT* $$/GEOM
014540,000049: 13,2070 43414 SVDWN2 BOF RVQ # SW=1=AVETOMID DOING W-MATRIX INTEG.
014541,000050: 13,2071 04756 AVEMIDSW
014542,000051: 13,2072 26073 +1
014543,000052: 13,2073 53775 VLOAD VSL*
014544,000053: 13,2074 01521 TDELTAV
014545,000054: 13,2075 57605 0 -7,2
014546,000055: 13,2076 53655 VAD VSL*
014547,000056: 13,2077 01535 RCV
014548,000057: 13,2100 57576 0,2
014549,000058: 13,2101 25221 STOVL RN
014550,000059: 13,2102 01527 TNUV
014551,000060: 13,2103 53257 VSL* VAD
014552,000061: 13,2104 57602 0 -4,2
014553,000062: 13,2105 01543 VCV
014554,000063: 13,2106 77657 VSL*
014555,000064: 13,2107 57576 0,2
014556,000065: 13,2110 15227 STODL VN
014557,000066: 13,2111 01517 TET
014558,000067: 13,2112 01235 STORE PIPTIME
014559,000068: 13,2113 77616 RVQ
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Page 335
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014561,000070: 13,2114 53775 SVDWN1 VLOAD VSL*
014562,000071: 13,2115 01521 TDELTAV
014563,000072: 13,2116 57605 0 -7,2
014564,000073: 13,2117 53655 VAD VSL*
014565,000074: 13,2120 01535 RCV
014566,000075: 13,2121 57576 0,2
014567,000076: 13,2122 25720 STOVL R-OTHER
014568,000077: 13,2123 01527 TNUV
014569,000078: 13,2124 53257 VSL* VAD
014570,000079: 13,2125 57602 0 -4,2
014571,000080: 13,2126 01543 VCV
014572,000081: 13,2127 77657 VSL*
014573,000082: 13,2130 57576 0,2
014574,000083: 13,2131 01726 STORE V-OTHER
014575,000084: 13,2132 77616 RVQ
014576,000085:
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Page 336
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014578,000087: # THE FOLLOWING ROUTINE TAKES A HALF UNIT TARGET VECTOR REFERRED TO NAV BASE COORDINATES AND FINDS BOTH
014579,000088: # GIMBAL ORIENTATIONS AT WHICH THE RR MIGHT SIGHT THE TARGET. THE GIMBAL ANGLES CORRESPONDING TO THE PRESENT MODE
014580,000089: # ARE LEFT IN MODEA AND THOSE WHICH WOULD BE USED AFTER A REMODE IN MODEB. THIS ROUTINE ASSUMES MODE 1 IS TRUNNION
014581,000090: # ANGLE LESS THAN 90 DEGS IN ABS VALUE WITH ARBITRARY SHAFT, WITH A CORRESPONDING DEFINITION FOR MODE 2. MODE
014582,000091: # SELECTION AND LIMIT CHECKING ARE DONE ELSEWHERE.
014583,000092:
014584,000093: # THE MODE 1 CONFIGURATION IS CALCULATED FROM THE VECTOR AND THEN MODE 2 IS FOUND USING THE RELATIONS
014585,000094:
014586,000095: # S(2) = 180 + S(1)
014587,000096: # T(2) = 180 - T(1)
014588,000097:
014589,000098: # THE VECTOR ARRIVES IN MPAC WHERE TRG*SMNG OR *SMNB* WILL HAVE LEFT IT.
014590,000099:
014591,000100: 13,2133 00041 RRANGLES STORE 32D
014592,000101: 13,2134 57545 DLOAD DCOMP # SINCE WE WILL FIND THE MODE 1 SHAFT
014593,000102: 13,2135 00043 34D # ANGLE LATER, WE CAN FIND THE MODE 1
014594,000103: 13,2136 67401 SETPD ASIN # TRUNNION BY SIMPLY TAKING THE ARCSIN OF
014595,000104: 13,2137 00001 0 # THE Y COMPONENT, THE ASIN GIVING AN
014596,000105: 13,2140 44206 PUSH BDSU # ANSWER WHOSE ABS VAL IS LESS THAN 90 DEG
014597,000106: 13,2141 22273 LODPHALF
014598,000107: 13,2142 14005 STODL 4 # MODE 2 TRUNNION TO 4.
014599,000108:
014600,000109: 13,2143 22275 LO6ZEROS
014601,000110: 13,2144 24043 STOVL 34D # UNIT THE PROJECTION OF THE VECTOR
014602,000111: 13,2145 00041 32D # IN THE X-Z PLANE
014603,000112: 13,2146 41056 UNIT BOVB # IF OVERFLOW, TARGET VECTOR IS ALONG Y
014604,000113: 13,2147 52421 LUNDESCH # CALL FOR MANEUVER UNLESS ON LUNAR SURF
014605,000114: 13,2150 14041 STODL 32D # PROJECTION VECTOR.
014606,000115: 13,2151 00041 32D
014607,000116: 13,2152 44142 SR1 STQ
014608,000117: 13,2153 00051 S2
014609,000118: 13,2154 14023 STODL SINTH # USE ARCTRIG SINCE SHAFT COULD BE ARB.
014610,000119: 13,2155 00045 36D
014611,000120: 13,2156 77742 SR1
014612,000121: 13,2157 34021 STCALL COSTH
014613,000122: 13,2160 47222 ARCTRIG
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Page 337
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014615,000124: 13,2161 43206 PUSH DAD # MODE 1 SHAFT TO 2.
014616,000125: 13,2162 22273 LODPHALF
014617,000126: 13,2163 24007 STOVL 6
014618,000127: 13,2164 00005 4
014619,000128: 13,2165 77634 RTB # FIND MODE 2 CDU ANGLES.
014620,000129: 13,2166 21541 2V1STO2S
014621,000130: 13,2167 25112 STOVL MODEB
014622,000131: 13,2170 00001 0
014623,000132: 13,2171 77634 RTB # MODE 1 ANGLES TO MODE A.
014624,000133: 13,2172 21541 2V1STO2S
014625,000134: 13,2173 01110 STORE MODEA
014626,000135: 13,2174 77776 EXIT
014627,000136:
014628,000137: 13,2175 40110 CS RADMODES # SWAP MODEA AND MODEB IF RR IN MODE 2.
014629,000138: 13,2176 74740 MASK BIT12
014630,000139: 13,2177 10000 CCS A
014631,000140: 13,2200 12204 TCF +4
014632,000141:
014633,000142: 13,2201 53110 DXCH MODEA
014634,000143: 13,2202 53112 DXCH MODEB
014635,000144: 13,2203 53110 DXCH MODEA
014636,000145:
014637,000146: 13,2204 06036 TC INTPRET
014638,000147: 13,2205 77650 GOTO
014639,000148: 13,2206 00051 S2
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Page 338
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014641,000150: # GIVEN RR TRUNNION AND SHAFT (T,S) IN TANGNB,+1, FIND THE ASSOCIATED
014642,000151: # LINE OF SIGHT IN NAV BASE AXES. THE HALF UNIT VECTOR, .5(SIN(S)COS(T),
014643,000152: # -SIN(T),COS(S)COS(T)) IS LEFT IN MPAC AND 32D.
014644,000153:
014645,000154: 23,2000 SETLOC INFLIGHT
014646,000155: 23,2000 BANK
014647,000156:
014648,000157: 23,2041 COUNT* $$/GEOM
014649,000158:
014650,000159: 23,2041 47135 RRNB SLOAD RTB
014651,000160: 23,2042 03751 TANGNB
014652,000161: 23,2043 21465 CDULOGIC
014653,000162: 23,2044 41401 SETPD PUSH # TRUNNION ANGLE TO 0
014654,000163: 23,2045 00001 0
014655,000164: 23,2046 57556 SIN DCOMP
014656,000165: 23,2047 14043 STODL 34D # Y COMPONENT
014657,000166:
014658,000167: 23,2050 41546 COS PUSH # .5 COS(T) TO 0
014659,000168: 23,2051 47135 SLOAD RTB
014660,000169: 23,2052 03752 TANGNB +1
014661,000170: 23,2053 21465 CDULOGIC
014662,000171: 23,2054 71406 PUSH COS # SHAFT ANGLE TO 2
014663,000172: 23,2055 72405 DMP SL1
014664,000173: 23,2056 00001 0
014665,000174: 23,2057 14045 STODL 36D # Z COMPONENT
014666,000175:
014667,000176: 23,2060 41356 SIN DMP
014668,000177: 23,2061 77752 SL1
014669,000178: 23,2062 24041 STOVL 32D
014670,000179: 23,2063 00041 32D
014671,000180: 23,2064 77616 RVQ
End of include-file LEM_GEOMETRY.agc. Parent file is MAIN.agc