Source Code
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These source-code files are part of a reconstructed copy of Luminary 97, the
second release of the Apollo 11 Lunar Module (LM) Apollo Guidance Computer
(AGC) software. It was created to fix two incorrect ephemeris constants in
Luminary 96, as described by anomaly report LNY-59.
The reconstruction began with source code of Luminary 99 revision 1 previously
transcribed from a digitized copy of that program. The code was then updated
by undoing changes described in original Luminary memos 83 and 85, using asterisks
indicating changed lines in the listing as a guide. The reconstruction was
verified by matching memory-bank checksums to those listed in drawing 2021152D.
Note that page numbers in the reconstructed code match those on the Luminary 099
revision 001 printout, although the added code would likely have changed page
numbers for a real Luminary 97 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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013170,000002: ## Copyright: Public domain.
013171,000003: ## Filename: LEM_GEOMETRY.agc
013172,000004: ## Purpose: A section of Luminary revision 97.
013173,000005: ## It is part of the reconstructed source code for the
013174,000006: ## second release of the flight software for the Lunar
013175,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
013176,000008: ## It was created to fix two incorrect ephemeris constants in
013177,000009: ## Luminary 96, as described by anomaly report LNY-59.
013178,000010: ## The code has been recreated from a copy of Luminary 99
013179,000011: ## revision 001, using asterisks indicating changed lines in
013180,000012: ## the listing and Luminary Memos #83 and #85, which list
013181,000013: ## changes between Luminary 97 and 98, and 98 and 99. The
013182,000014: ## code has been adapted such that the resulting bugger words
013183,000015: ## exactly match those specified for Luminary 97 in NASA drawing
013184,000016: ## 2021152D, which gives relatively high confidence that the
013185,000017: ## reconstruction is correct.
013186,000018: ## Reference: pp. 320-325
013187,000019: ## Assembler: yaYUL
013188,000020: ## Contact: Ron Burkey <info@sandroid.org>.
013189,000021: ## Website: www.ibiblio.org/apollo/index.html
013190,000022: ## Mod history: 2019-07-28 MAS Created from Luminary 99.
013191,000023:
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Page 320
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013193,000025: 23,2041 BANK 23
013194,000026: 13,2000 SETLOC LEMGEOM
013195,000027: 13,2000 BANK
013196,000028:
013197,000029: 13,2070 30,2000 SBANK= LOWSUPER
013198,000030: 13,2070 E5,1642 EBANK= XSM
013199,000031:
013200,000032: # THESE TWO ROUTINES COMPUTE THE ACTUAL STATE VECTOR FOR LM,CSM BY ADDING
013201,000033: # THE CONIC R,V AND THE DEVIATIONS R,V. THE STATE VECTORS ARE CONVERTED TO
013202,000034: # METERS B-29 AND METERS/CSEC B-7 AND STORED APPROPRIATELY IN RN,VN OR
013203,000035: # R-OTHER,V-OTHER FOR DOWNLINK. THE ROUTINES NAMES ARE SWITCHED IN THE
013204,000036: # OTHER VEHICLES COMPUTER.
013205,000037:
013206,000038: # INPUT
013207,000039: # STATE VECTOR IN TEMPORARY STORAGE AREA
013208,000040: # IF STATE VECTOR IS SCALED POS B27 AND VEL B5
013209,000041: # SET X2 TO +2
013210,000042: # IF STATE VECTOR IS SCALED POS B29 AND VEL B7
013211,000043: # SET X2 TO 0
013212,000044:
013213,000045: # OUTPUT
013214,000046: # R(T) IN RN, V(T) IN VN, T IN PIPTIME
013215,000047: # OR
013216,000048: # R(T) IN R-OTHER, V(T) IN V-OTHER (T IS DEFINED BY T-OTHER)
013217,000049:
013218,000050: 13,2070 COUNT* $$/GEOM
013219,000051: 13,2070 43414 SVDWN2 BOF RVQ # SW=1=AVETOMID DOING W-MATRIX INTEG.
013220,000052: 13,2071 04756 AVEMIDSW
013221,000053: 13,2072 26073 +1
013222,000054: 13,2073 53775 VLOAD VSL*
013223,000055: 13,2074 01521 TDELTAV
013224,000056: 13,2075 57605 0 -7,2
013225,000057: 13,2076 53655 VAD VSL*
013226,000058: 13,2077 01535 RCV
013227,000059: 13,2100 57576 0,2
013228,000060: 13,2101 25221 STOVL RN
013229,000061: 13,2102 01527 TNUV
013230,000062: 13,2103 53257 VSL* VAD
013231,000063: 13,2104 57602 0 -4,2
013232,000064: 13,2105 01543 VCV
013233,000065: 13,2106 77657 VSL*
013234,000066: 13,2107 57576 0,2
013235,000067: 13,2110 15227 STODL VN
013236,000068: 13,2111 01517 TET
013237,000069: 13,2112 01235 STORE PIPTIME
013238,000070: 13,2113 77616 RVQ
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Page 321
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013240,000072: 13,2114 53775 SVDWN1 VLOAD VSL*
013241,000073: 13,2115 01521 TDELTAV
013242,000074: 13,2116 57605 0 -7,2
013243,000075: 13,2117 53655 VAD VSL*
013244,000076: 13,2120 01535 RCV
013245,000077: 13,2121 57576 0,2
013246,000078: 13,2122 25720 STOVL R-OTHER
013247,000079: 13,2123 01527 TNUV
013248,000080: 13,2124 53257 VSL* VAD
013249,000081: 13,2125 57602 0 -4,2
013250,000082: 13,2126 01543 VCV
013251,000083: 13,2127 77657 VSL*
013252,000084: 13,2130 57576 0,2
013253,000085: 13,2131 01726 STORE V-OTHER
013254,000086: 13,2132 77616 RVQ
013255,000087:
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Page 322
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013257,000089: # THE FOLLOWING ROUTINE TAKES A HALF UNIT TARGET VECTOR REFERRED TO NAV BASE COORDINATES AND FINDS BOTH
013258,000090: # GIMBAL ORIENTATIONS AT WHICH THE RR MIGHT SIGHT THE TARGET. THE GIMBAL ANGLES CORRESPONDING TO THE PRESENT MODE
013259,000091: # ARE LEFT IN MODEA AND THOSE WHICH WOULD BE USED AFTER A REMODE IN MODEB. THIS ROUTINE ASSUMES MODE 1 IS TRUNNION
013260,000092: # ANGLE LESS THAN 90 DEGS IN ABS VALUE WITH ARBITRARY SHAFT, WITH A CORRESPONDING DEFINITION FOR MODE 2. MODE
013261,000093: # SELECTION AND LIMIT CHECKING ARE DONE ELSEWHERE.
013262,000094:
013263,000095: # THE MODE 1 CONFIGURATION IS CALCULATED FROM THE VECTOR AND THEN MODE 2 IS FOUND USING THE RELATIONS
013264,000096:
013265,000097: # S(2) = 180 + S(1)
013266,000098: # T(2) = 180 - T(1)
013267,000099:
013268,000100: # THE VECTOR ARRIVES IN MPAC WHERE TRG*SMNG OR *SMNB* WILL HAVE LEFT IT.
013269,000101:
013270,000102: 13,2133 00041 RRANGLES STORE 32D
013271,000103: 13,2134 57545 DLOAD DCOMP # SINCE WE WILL FIND THE MODE 1 SHAFT
013272,000104: 13,2135 00043 34D # ANGLE LATER, WE CAN FIND THE MODE 1
013273,000105: 13,2136 67401 SETPD ASIN # TRUNNION BY SIMPLY TAKING THE ARCSIN OF
013274,000106: 13,2137 00001 0 # THE Y COMPONENT, THE ASIN GIVING AN
013275,000107: 13,2140 44206 PUSH BDSU # ANSWER WHOSE ABS VAL IS LESS THAN 90 DEG
013276,000108: 13,2141 24005 LODPHALF
013277,000109: 13,2142 14005 STODL 4 # MODE 2 TRUNNION TO 4.
013278,000110:
013279,000111: 13,2143 24007 LO6ZEROS
013280,000112: 13,2144 24043 STOVL 34D # UNIT THE PROJECTION OF THE VECTOR
013281,000113: 13,2145 00041 32D # IN THE X-Z PLANE
013282,000114: 13,2146 41056 UNIT BOVB # IF OVERFLOW, TARGET VECTOR IS ALONG Y
013283,000115: 13,2147 52421 LUNDESCH # CALL FOR MANEUVER UNLESS ON LUNAR SURF
013284,000116: 13,2150 14041 STODL 32D # PROJECTION VECTOR.
013285,000117: 13,2151 00041 32D
013286,000118: 13,2152 44142 SR1 STQ
013287,000119: 13,2153 00051 S2
013288,000120: 13,2154 14023 STODL SINTH # USE ARCTRIG SINCE SHAFT COULD BE ARB.
013289,000121: 13,2155 00045 36D
013290,000122: 13,2156 77742 SR1
013291,000123: 13,2157 34021 STCALL COSTH
013292,000124: 13,2160 47320 ARCTRIG
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Page 323
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013294,000126: 13,2161 43206 PUSH DAD # MODE 1 SHAFT TO 2.
013295,000127: 13,2162 24005 LODPHALF
013296,000128: 13,2163 24007 STOVL 6
013297,000129: 13,2164 00005 4
013298,000130: 13,2165 77634 RTB # FIND MODE 2 CDU ANGLES.
013299,000131: 13,2166 21635 2V1STO2S
013300,000132: 13,2167 25112 STOVL MODEB
013301,000133: 13,2170 00001 0
013302,000134: 13,2171 77634 RTB # MODE 1 ANGLES TO MODE A.
013303,000135: 13,2172 21635 2V1STO2S
013304,000136: 13,2173 01110 STORE MODEA
013305,000137: 13,2174 77776 EXIT
013306,000138:
013307,000139: 13,2175 40110 CS RADMODES # SWAP MODEA AND MODEB IF RR IN MODE 2.
013308,000140: 13,2176 74740 MASK ANTENBIT
013309,000141: 13,2177 10000 CCS A
013310,000142: 13,2200 12204 TCF +4
013311,000143:
013312,000144: 13,2201 53110 DXCH MODEA
013313,000145: 13,2202 53112 DXCH MODEB
013314,000146: 13,2203 53110 DXCH MODEA
013315,000147:
013316,000148: 13,2204 06037 TC INTPRET
013317,000149: 13,2205 77650 GOTO
013318,000150: 13,2206 00051 S2
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Page 324
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013320,000152: # GIVEN RR TRUNNION AND SHAFT (T,S) IN TANGNB,+1, FIND THE ASSOCIATED
013321,000153: # LINE OF SIGHT IN NAV BASE AXES. THE HALF UNIT VECTOR, .5(SIN(S)COS(T),
013322,000154: # -SIN(T),COS(S)COS(T)) IS LEFT IN MPAC AND 32D.
013323,000155:
013324,000156: 23,2000 SETLOC INFLIGHT
013325,000157: 23,2000 BANK
013326,000158:
013327,000159: 23,2041 COUNT* $$/GEOM
013328,000160:
013329,000161: 23,2041 47135 RRNB SLOAD RTB
013330,000162: 23,2042 03753 TANGNB
013331,000163: 23,2043 21576 CDULOGIC
013332,000164: 23,2044 41401 SETPD PUSH # TRUNNION ANGLE TO 0
013333,000165: 23,2045 00001 0
013334,000166: 23,2046 57556 SIN DCOMP
013335,000167: 23,2047 14043 STODL 34D # Y COMPONENT
013336,000168:
013337,000169: 23,2050 41546 COS PUSH # .5 COS(T) TO 0
013338,000170: 23,2051 47135 SLOAD RTB
013339,000171: 23,2052 03754 TANGNB +1
013340,000172: 23,2053 21576 CDULOGIC
013341,000173: 23,2054 71406 RRNB1 PUSH COS # SHAFT ANGLE TO 2
013342,000174: 23,2055 72405 DMP SL1
013343,000175: 23,2056 00001 0
013344,000176: 23,2057 14045 STODL 36D # Z COMPONENT
013345,000177:
013346,000178: 23,2060 41356 SIN DMP
013347,000179: 23,2061 77752 SL1
013348,000180: 23,2062 24041 STOVL 32D
013349,000181: 23,2063 00041 32D
013350,000182: 23,2064 77616 RVQ
013351,000183:
013352,000184: # THIS ENTRY TO RRNB REQUIRES THE TRUNNION AND SHAFT ANGLES IN MPAC AND MPAC +1 RESPECTIVELY
013353,000185:
013354,000186: 23,2065 14025 RRNBMPAC STODL 20D # SAVE SHAFT CDU IN 21.
013355,000187: 23,2066 00155 MPAC # SET MODE TO DP. (THE PRECEEDING STORE
013356,000188: # MAY BE DP, TP OR VECTOR.)
013357,000189: 23,2067 40234 RTB SETPD
013358,000190: 23,2070 21576 CDULOGIC
013359,000191: 23,2071 00001 0
013360,000192: 23,2072 73406 PUSH SIN # TRUNNION ANGLE TO 0
013361,000193: 23,2073 77676 DCOMP
013362,000194: 23,2074 14043 STODL 34D # Y COMPONENT
013363,000195: 23,2075 41546 COS PUSH # .5COS(T) TO 0
013364,000196: 23,2076 47135 SLOAD RTB # PICK UP CDU'S.
013365,000197: 23,2077 00026 21D
013366,000198: 23,2100 21576 CDULOGIC
013367,000199: 23,2101 77650 GOTO
013368,000200: 23,2102 46054 RRNB1
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Page 325
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013371,000203:
013372,000204:
End of include-file LEM_GEOMETRY.agc. Parent file is MAIN.agc