Source Code
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These source-code files are part of a reconstructed copy of LUM69 Revision 2, the
flown Apollo 10 Lunar Module (LM) Apollo Guidance Computer (AGC) software.
The reconstruction began with source code of Luminary 69 revision 0 previously
transcribed from a digitized copy of that program. The code was then updated
by back-porting the R-2 lunar potential model from previously-transcribed source
code of Luminary 99. These required changes were described in the original
Luminary memos 75 and 78. The reconstructed code was verified by
matching memory-bank checksums to those listed in drawing 2021152G. Note that
page numbers in the reconstructed code match those on the Luminary 069 printout,
although the added code would likely have changed page numbers for a real LUM69
Revision 2 listing.
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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014437,000002: ## Copyright: Public domain.
014438,000003: ## Filename: LEM_GEOMETRY.agc
014439,000004: ## Purpose: A section of LUM69 revision 2.
014440,000005: ## It is part of the reconstructed source code for the flown
014441,000006: ## version of the flight software for the Lunar Module's (LM)
014442,000007: ## Apollo Guidance Computer (AGC) for Apollo 10. The code has
014443,000008: ## been recreated from a copy of Luminary revsion 069, using
014444,000009: ## changes present in Luminary 099 which were described in
014445,000010: ## Luminary memos 75 and 78. The code has been adapted such
014446,000011: ## that the resulting bugger words exactly match those specified
014447,000012: ## for LUM69 revision 2 in NASA drawing 2021152B, which gives
014448,000013: ## relatively high confidence that the reconstruction is correct.
014449,000014: ## Reference: pp. 334-338
014450,000015: ## Assembler: yaYUL
014451,000016: ## Contact: Ron Burkey <info@sandroid.org>.
014452,000017: ## Website: www.ibiblio.org/apollo/index.html
014453,000018: ## Mod history: 2019-07-27 MAS Created from Luminary 69.
014454,000019:
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Page 334
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014456,000021: 23,2041 BANK 23
014457,000022: 13,2000 SETLOC LEMGEOM
014458,000023: 13,2000 BANK
014459,000024:
014460,000025: 13,2070 30,2000 SBANK= LOWSUPER
014461,000026: 13,2070 E5,1642 EBANK= XSM
014462,000027:
014463,000028: # THESE TWO ROUTINES COMPUTE THE ACTUAL STATE VECTOR FOR LM,CSM BY ADDING
014464,000029: # THE CONIC R,V AND THE DEVIATIONSR,V. THE STATE VECTORS ARE CONVERTED TO
014465,000030: # METERS B-29 AND METERS/CSEC B-7 AND STORED APPROPRIATELY IN RN,VN OR
014466,000031: # R-OTHER , V-OTHER FOR DOWNLINK. THE ROUTINES NAMES ARE SWITCHED IN THE
014467,000032: # OTHER VEHICLES COMPUTER.
014468,000033:
014469,000034: # INPUT
014470,000035: # STATE VECTOR IN TEMPORARY STORAGE AREA
014471,000036: # IF STATE VECTOR IS SCALED POS B27 AND VEL B5
014472,000037: # SET X2 TO +2
014473,000038: # IF STATE VECTOR IS SCALED POS B29 AND VEL B7
014474,000039: # SET X2 TO 0
014475,000040:
014476,000041: # OUTPUT
014477,000042: # R(T) IN RN, V(T) IN VN, T IN PIPTIME
014478,000043: # OR
014479,000044: # R(T) IN R-OTHER, V(T) IN V-OTHER (T IS DEFINED BY T-OTHER)
014480,000045:
014481,000046: 13,2070 COUNT* $$/GEOM
014482,000047: 13,2070 43414 SVDWN2 BOF RVQ # SW=1=AVETOMID DOING W-MATRIX INTEG.
014483,000048: 13,2071 04756 AVEMIDSW
014484,000049: 13,2072 26073 +1
014485,000050: 13,2073 53775 VLOAD VSL*
014486,000051: 13,2074 01521 TDELTAV
014487,000052: 13,2075 57605 0 -7,2
014488,000053: 13,2076 53655 VAD VSL*
014489,000054: 13,2077 01535 RCV
014490,000055: 13,2100 57576 0,2
014491,000056: 13,2101 25221 STOVL RN
014492,000057: 13,2102 01527 TNUV
014493,000058: 13,2103 53257 VSL* VAD
014494,000059: 13,2104 57602 0 -4,2
014495,000060: 13,2105 01543 VCV
014496,000061: 13,2106 77657 VSL*
014497,000062: 13,2107 57576 0,2
014498,000063: 13,2110 15227 STODL VN
014499,000064: 13,2111 01517 TET
014500,000065: 13,2112 01235 STORE PIPTIME
014501,000066: 13,2113 77616 RVQ
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Page 335
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014503,000068: 13,2114 53775 SVDWN1 VLOAD VSL*
014504,000069: 13,2115 01521 TDELTAV
014505,000070: 13,2116 57605 0 -7,2
014506,000071: 13,2117 53655 VAD VSL*
014507,000072: 13,2120 01535 RCV
014508,000073: 13,2121 57576 0,2
014509,000074: 13,2122 25720 STOVL R-OTHER
014510,000075: 13,2123 01527 TNUV
014511,000076: 13,2124 53257 VSL* VAD
014512,000077: 13,2125 57602 0 -4,2
014513,000078: 13,2126 01543 VCV
014514,000079: 13,2127 77657 VSL*
014515,000080: 13,2130 57576 0,2
014516,000081: 13,2131 01726 STORE V-OTHER
014517,000082: 13,2132 77616 RVQ
014518,000083:
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Page 336
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014520,000085: # THE FOLLOWING ROUTINE TAKES A HALF UNIT TARGET VECTOR REFERRED TO NAV BASE COORDINATES AND FINDS BOTH
014521,000086: # GIMBAL ORIENTATIONS AT WHICH THE RR MIGHT SIGHT THE TARGET. THE GIMBAL ANGLES CORRESPONDING TO THE PRESENT MODE
014522,000087: # ARE LEFT IN MODEA AND THOSE WHICH WOULD BE USED AFTER A REMODE IN MODEB. THIS ROUTINE ASSUMES MODE 1 IS TRUNNION
014523,000088: # ANGLE LESS THAN 90 DEGS IN ABS VALUE WITH ARBITRARY SHAFT, WITH A CORRESPONDING DEFINITION FOR MODE 2. MODE
014524,000089: # SELECTION AND LIMIT CHECKING ARE DONE ELSEWHERE.
014525,000090:
014526,000091: # THE MODE 1 CONFIGURATION IS CALCULATED FROM THE VECTOR AND THEN MODE 2 IS FOUND USING THE RELATIONS
014527,000092:
014528,000093: # S(2) = 180 + S(1)
014529,000094: # T(2) = 180 - T(1)
014530,000095:
014531,000096: # THE VECTOR ARRIVES IN MPAC WHERE TRG*SMNG OR *SMNB* WILL HAVE LEFT IT.
014532,000097:
014533,000098: 13,2133 00041 RRANGLES STORE 32D
014534,000099: 13,2134 57545 DLOAD DCOMP # SINCE WE WILL FIND THE MODE 1 SHAFT
014535,000100: 13,2135 00043 34D # ANGLE LATER, WE CAN FIND THE MODE 1
014536,000101: 13,2136 67401 SETPD ASIN # TRUNNION BY SIMPLY TAKING THE ARCSIN OF
014537,000102: 13,2137 00001 0 # THE Y COMPONENT, THE ASIN GIVING AN
014538,000103: 13,2140 44206 PUSH BDSU # ANSWER WHOSE ABS VAL IS LESS THAN 90 DEG
014539,000104: 13,2141 22273 LODPHALF
014540,000105: 13,2142 14005 STODL 4 # MODE 2 TRUNNION TO 4.
014541,000106:
014542,000107: 13,2143 22275 LO6ZEROS
014543,000108: 13,2144 24043 STOVL 34D # UNIT THE PROJECTION OF THE VECTOR
014544,000109: 13,2145 00041 32D # IN THE X-Z PLANE
014545,000110: 13,2146 41056 UNIT BOVB # IF OVERFLOW, TARGET VECTOR IS ALONG Y
014546,000111: 13,2147 52421 LUNDESCH # CALL FOR MANEUVER UNLESS ON LUNAR SURF
014547,000112: 13,2150 14041 STODL 32D # PROJECTION VECTOR.
014548,000113: 13,2151 00041 32D
014549,000114: 13,2152 44142 SR1 STQ
014550,000115: 13,2153 00051 S2
014551,000116: 13,2154 14023 STODL SINTH # USE ARCTRIG SINCE SHAFT COULD BE ARB.
014552,000117: 13,2155 00045 36D
014553,000118: 13,2156 77742 SR1
014554,000119: 13,2157 34021 STCALL COSTH
014555,000120: 13,2160 47222 ARCTRIG
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Page 337
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014557,000122: 13,2161 43206 PUSH DAD # MODE 1 SHAFT TO 2.
014558,000123: 13,2162 22273 LODPHALF
014559,000124: 13,2163 24007 STOVL 6
014560,000125: 13,2164 00005 4
014561,000126: 13,2165 77634 RTB # FIND MODE 2 CDU ANGLES.
014562,000127: 13,2166 21541 2V1STO2S
014563,000128: 13,2167 25112 STOVL MODEB
014564,000129: 13,2170 00001 0
014565,000130: 13,2171 77634 RTB # MODE 1 ANGLES TO MODE A.
014566,000131: 13,2172 21541 2V1STO2S
014567,000132: 13,2173 01110 STORE MODEA
014568,000133: 13,2174 77776 EXIT
014569,000134:
014570,000135: 13,2175 40110 CS RADMODES # SWAP MODEA AND MODEB IF RR IN MODE 2.
014571,000136: 13,2176 74740 MASK ANTENBIT
014572,000137: 13,2177 10000 CCS A
014573,000138: 13,2200 12204 TCF +4
014574,000139:
014575,000140: 13,2201 53110 DXCH MODEA
014576,000141: 13,2202 53112 DXCH MODEB
014577,000142: 13,2203 53110 DXCH MODEA
014578,000143:
014579,000144: 13,2204 06036 TC INTPRET
014580,000145: 13,2205 77650 GOTO
014581,000146: 13,2206 00051 S2
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Page 338
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014583,000148: # GIVEN RR TRUNNION AND SHAFT (T,S) IN TANGNB,+1, FIND THE ASSOCIATED
014584,000149: # LINE OF SIGHT IN NAV BASE AXES. THE HALF UNIT VECTOR, .5(SIN(S)COS(T),
014585,000150: # -SIN(T),COS(S)COS(T)) IS LEFT IN MPAC AND 32D.
014586,000151:
014587,000152: 23,2000 SETLOC INFLIGHT
014588,000153: 23,2000 BANK
014589,000154:
014590,000155: 23,2041 COUNT* $$/GEOM
014591,000156:
014592,000157: 23,2041 47135 RRNB SLOAD RTB
014593,000158: 23,2042 03751 TANGNB
014594,000159: 23,2043 21465 CDULOGIC
014595,000160: 23,2044 41401 SETPD PUSH # TRUNNION ANGLE TO 0
014596,000161: 23,2045 00001 0
014597,000162: 23,2046 57556 SIN DCOMP
014598,000163: 23,2047 14043 STODL 34D # Y COMPONENT
014599,000164:
014600,000165: 23,2050 41546 COS PUSH # .5 COS(T) TO 0
014601,000166: 23,2051 47135 SLOAD RTB
014602,000167: 23,2052 03752 TANGNB +1
014603,000168: 23,2053 21465 CDULOGIC
014604,000169: 23,2054 71406 PUSH COS # SHAFT ANGLE TO 2
014605,000170: 23,2055 72405 DMP SL1
014606,000171: 23,2056 00001 0
014607,000172: 23,2057 14045 STODL 36D # Z COMPONENT
014608,000173:
014609,000174: 23,2060 41356 SIN DMP
014610,000175: 23,2061 77752 SL1
014611,000176: 23,2062 24041 STOVL 32D
014612,000177: 23,2063 00041 32D
014613,000178: 23,2064 77616 RVQ
End of include-file LEM_GEOMETRY.agc. Parent file is MAIN.agc