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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048290,000002: ## Copyright: Public domain.
048291,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
048292,000004: ## Purpose: A section of LUM69 revision 2.
048293,000005: ## It is part of the reconstructed source code for the flown
048294,000006: ## version of the flight software for the Lunar Module's (LM)
048295,000007: ## Apollo Guidance Computer (AGC) for Apollo 10. The code has
048296,000008: ## been recreated from a copy of Luminary revsion 069, using
048297,000009: ## changes present in Luminary 099 which were described in
048298,000010: ## Luminary memos 75 and 78. The code has been adapted such
048299,000011: ## that the resulting bugger words exactly match those specified
048300,000012: ## for LUM69 revision 2 in NASA drawing 2021152B, which gives
048301,000013: ## relatively high confidence that the reconstruction is correct.
048302,000014: ## Reference: pp. 1128-1134
048303,000015: ## Assembler: yaYUL
048304,000016: ## Contact: Ron Burkey <info@sandroid.org>.
048305,000017: ## Website: www.ibiblio.org/apollo/index.html
048306,000018: ## Mod history: 2019-07-27 MAS Created from Luminary 69.
048307,000019:
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Page 1128
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048309,000021: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
048310,000022:
048311,000023: # CALLING SEQUENCE
048312,000024: # L-1 CALL
048313,000025: # L LAT-LONG
048314,000026:
048315,000027: # SUBROUTINES USED
048316,000028: # R-TO-RP,ARCTAN,SETGAMMA,SETRE
048317,000029:
048318,000030: # ERASABLE INIT. REQ.
048319,000031: # AXO,-AYO,AZO,TEPHEM (SET AT LAUNCH TIME)
048320,000032: # ALPHAV = POSITION VECTOR METERS B-29
048321,000033: # MPAC-- TIME (CSECS B-28)
048322,000034: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
048323,000035: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
048324,000036:
048325,000037: # OUTPUT
048326,000038: # LATITUDE IN LAT (REVS. B-0)
048327,000039: # LONGITUDE IN LONG (REVS. B-0)
048328,000040: # ALTITUDE IN ALT METERS B-29
048329,000041:
048330,000042: 30,3746 BANK 30
048331,000043: 13,2000 SETLOC LATLONG
048332,000044: 13,2000 BANK
048333,000045:
048334,000046: 13,2351 COUNT* $$/LT-LG
048335,000047: 13,2351 E4,1431 EBANK= ALPHAV
048336,000048: 13,2351 40220 LAT-LONG STQ SETPD
048337,000049: 13,2352 03672 INCORPEX
048338,000050: 13,2353 00001 0D
048339,000051: 13,2354 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
048340,000052: 13,2355 02032 ALPHAV
048341,000053: 13,2356 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
048342,000054: 13,2357 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
048343,000055: 13,2360 22275 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
048344,000056: 13,2361 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
048345,000057: 13,2362 01743 LUNAFLAG # 0=EARTH, 1=MOON
048346,000058: 13,2363 26364 CALLRTRP
048347,000059: 13,2364 77624 CALLRTRP CALL
048348,000060: 13,2365 51531 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
048349,000061: 13,2366 77656 UNIT # UNIT RP B-1
048350,000062: 13,2367 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
048351,000063: 13,2370 26550 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH,=1 FOR MOON
048352,000064: 13,2371 77624 CALL # SCALED B-1
048353,000065: 13,2372 26560 SETRE # CALC RE METERS B-29
048354,000066: 13,2373 63545 DLOAD DSQ
048355,000067: 13,2374 02032 ALPHAV
048356,000068: 13,2375 63525 PDDL DSQ
048357,000069: 13,2376 02034 ALPHAV +2
048358,000070: 13,2377 75415 DAD SQRT
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Page 1129
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048360,000072: 13,2400 76405 DMP SL1R
048361,000073: 13,2401 00011 GAMRP
048362,000074: 13,2402 14021 STODL COSTH # COS(LAT) B-1
048363,000075: 13,2403 02036 ALPHAV +4
048364,000076: 13,2404 34023 STCALL SINTH # SIN(LAT) B-1
048365,000077: 13,2405 26510 ARCTAN
048366,000078: 13,2406 15121 STODL LAT # LAT B0
048367,000079: 13,2407 02032 ALPHAV
048368,000080: 13,2410 14021 STODL COSTH # COS(LONG) B-1
048369,000081: 13,2411 02034 ALPHAV +2
048370,000082: 13,2412 34023 STCALL SINTH # SIN(LONG) B-1
048371,000083: 13,2413 26510 ARCTAN
048372,000084: 13,2414 15123 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
048373,000085: 13,2415 02070 ALPHAM
048374,000086: 13,2416 77625 DSU # ALT= R-RE METERS B-29
048375,000087: 13,2417 03671 ERADM
048376,000088: 13,2420 35125 STCALL ALT # EXIT WITH ALT METERS B-29
048377,000089: 13,2421 03672 INCORPEX
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Page 1130
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048379,000091: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
048380,000092:
048381,000093: # CALLING SEQUENCE
048382,000094: # L-1 CALL
048383,000095: # L LALOTORV
048384,000096:
048385,000097: # SUBROUTINES USED
048386,000098: # SETGAMMA,SETRE,RP-TO-R
048387,000099:
048388,000100: # ERASABLE INIT. REQ.
048389,000101: # AXO,AYO,AZO,TEPHEM SET AT LAUNCH TIME
048390,000102: # LAT-- LATITUDE (REVS B0)
048391,000103: # LONG-- LONGITUDE (REVS B0)
048392,000104: # ALT--ALTITUDE (METERS) B-29
048393,000105: # MPAC-- TIME (CSECS B-28)
048394,000106: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
048395,000107: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
048396,000108:
048397,000109: # OUTPUT
048398,000110: # R-VECTOR IN ALPHAV (METERS B-29)
048399,000111:
048400,000112: 13,2422 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
048401,000113: 13,2423 03672 INCORPEX
048402,000114: 13,2424 00001 0D
048403,000115: 13,2425 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
048404,000116: 13,2426 26550 SETGAMMA # GAMMA=B2/A2 FOR EARTH,1 FOR MOON B-1
048405,000117: 13,2427 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
048406,000118: 13,2430 01121 LAT # UNIT RP= SIN(LONG)COS(LAT) 2-3D
048407,000119: 13,2431 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
048408,000120: 13,2432 00011 GAMRP
048409,000121: 13,2433 01121 LAT # 0-1D= GAMMA*SIN(LAT) B-2
048410,000122: 13,2434 65346 COS PDDL # PD 4 2-3D=COS(LAT) B-1 TEMPORARILY
048411,000123: 13,2435 01123 LONG
048412,000124: 13,2436 57356 SIN DMPR # PD 2
048413,000125: 13,2437 71525 PDDL COS # PD 4 2-3D=SIN(LONG)COS(LAT) B-2
048414,000126: 13,2440 01121 LAT
048415,000127: 13,2441 71525 PDDL COS # PD 6 4-5D=COS(LAT) B-1 TEMPORARILY
048416,000128: 13,2442 01123 LONG
048417,000129: 13,2443 55475 DMPR VDEF # PD 4 MPAC= COS(LONG)COS(LAT) B-2
048418,000130: 13,2444 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
048419,000131: 13,2445 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
048420,000132: 13,2446 26560 SETRE # RE METERS B-29
048421,000133: 13,2447 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
048422,000134: 13,2450 22275 ZEROVEC
048423,000135: 13,2451 01743 LUNAFLAG
048424,000136: 13,2452 26454 CALLRPRT
048425,000137: 13,2453 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
048426,000138: 13,2454 77624 CALLRPRT CALL
048427,000139: 13,2455 51504 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
048428,000140: 13,2456 16032 STODL ALPHAV
048429,000141: 13,2457 03671 ERADM
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Page 1131
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048431,000143: 13,2460 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
048432,000144: 13,2461 01125 ALT
048433,000145: 13,2462 02032 ALPHAV
048434,000146: 13,2463 77772 VSL1 # R METERS B-29
048435,000147: 13,2464 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
048436,000148: 13,2465 03672 INCORPEX
048437,000149:
048438,000150: # SUBROUTINE TO COMPUTE EARTH RADIUS
048439,000151:
048440,000152: # INPUT
048441,000153: # 1/2 SIN LAT IN ALPHAV +4
048442,000154:
048443,000155: # OUTPUT
048444,000156: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
048445,000157:
048446,000158: 13,2466 63545 GETERAD DLOAD DSQ
048447,000159: 13,2467 02036 ALPHAV +4 # SIN**2(L)
048448,000160: 13,2470 44352 SL1 BDSU
048449,000161: 13,2471 22273 DP1/2 # COS**2(L)
048450,000162: 13,2472 44275 DMPR BDSU
048451,000163: 13,2473 26507 EE
048452,000164: 13,2474 22273 DP1/2
048453,000165: 13,2475 75465 BDDV SQRT
048454,000166: 13,2476 26503 B2XSC
048455,000167: 13,2477 77622 SR4R
048456,000168: 13,2500 03671 STORE ERADM
048457,000169: 13,2501 77616 RVQ
048458,000170:
048459,000171: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
048460,000172: # B2XSC= B**2 SCALED B-51
048461,000173: # B2/A2= B**2/A**2 SCALED B-1
048462,000174: # EE=(1-B**2/A**2) SCALED B-0
048463,000175:
048464,000176: 13,2502 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
048465,000177: 13,2504 11,2272 DP1/2 = XUNIT
048466,000178: 13,2504 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
048467,000179: 13,2506 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
048468,000180:
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Page 1132
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048470,000182: # ARCTAN SUBROUTINE
048471,000183:
048472,000184: # CALLING SEQUENCE
048473,000185: # SIN THETA IN SINTH B-1
048474,000186: # COS THETA IN COSTH B-1
048475,000187: # CALL ARCTAN
048476,000188:
048477,000189: # OUTPUT
048478,000190: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
048479,000191:
048480,000192: 13,2510 77600 ARCTAN BOV
048481,000193: 13,2511 26512 CLROVFLW
048482,000194: 13,2512 63545 CLROVFLW DLOAD DSQ
048483,000195: 13,2513 00023 SINTH
048484,000196: 13,2514 63525 PDDL DSQ
048485,000197: 13,2515 00021 COSTH
048486,000198: 13,2516 77615 DAD
048487,000199: 13,2517 75454 BZE SQRT
048488,000200: 13,2520 26536 ARCTANXX # ATAN=0/0 SET THETA=0
048489,000201: 13,2521 40065 BDDV BOV
048490,000202: 13,2522 00023 SINTH
048491,000203: 13,2523 26543 ATAN=90
048492,000204: 13,2524 67542 SR1 ASIN
048493,000205: 13,2525 00025 STORE THETA
048494,000206: 13,2526 50125 PDDL BMN
048495,000207: 13,2527 00021 COSTH
048496,000208: 13,2530 26532 NEGCOS
048497,000209: 13,2531 43545 DLOAD RVQ
048498,000210: 13,2532 57545 NEGCOS DLOAD DCOMP
048499,000211: 13,2533 43244 BPL DAD
048500,000212: 13,2534 26540 NEGOUT
048501,000213: 13,2535 22273 DP1/2
048502,000214: 13,2536 00025 ARCTANXX STORE THETA
048503,000215: 13,2537 77616 RVQ
048504,000216:
048505,000217: 13,2540 52025 NEGOUT DSU GOTO
048506,000218: 13,2541 22273 DP1/2
048507,000219: 13,2542 26536 ARCTANXX
048508,000220: 13,2543 75345 ATAN=90 DLOAD SIGN
048509,000221: 13,2544 10760 LODP1/4
048510,000222: 13,2545 00023 SINTH
048511,000223: 13,2546 00025 STORE THETA
048512,000224: 13,2547 77616 RVQ
048513,000225:
048514,000226: 13,2550 11,2274 2DZERO = DPZERO
048515,000227:
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Page 1133
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048517,000229: # ..... SETGAMMA SUBROUTINE .....
048518,000230: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
048519,000231:
048520,000232: # GAMMA = B**2/A**2 FOR EARTH (B-1)
048521,000233: # GAMMA = 1 FOR MOON (B-1)
048522,000234:
048523,000235: # CALLING SEQUENCE
048524,000236: # L CALL
048525,000237: # L+1 SETGAMMA
048526,000238:
048527,000239: # INPUT
048528,000240: # LUNAFLAG=0 FOR EARTH,=1 FOR MOON
048529,000241:
048530,000242: # OUTPUT
048531,000243: # GAMMA IN GAMRP (B-1)
048532,000244:
048533,000245: 13,2550 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
048534,000246: 13,2551 26505 B2/A2 # EARTH GAMMA
048535,000247: 13,2552 01743 LUNAFLAG
048536,000248: 13,2553 26556 SETGMEX
048537,000249: 13,2554 77735 SLOAD
048538,000250: 13,2555 22273 1B1 # MOON GAMMA
048539,000251: 13,2556 00011 SETGMEX STORE GAMRP
048540,000252: 13,2557 77616 RVQ
048541,000253: 13,2560 GAMRP = 8D
048542,000254:
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Page 1134
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048544,000256: # ..... SETRE SUBROUTINE .....
048545,000257: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
048546,000258:
048547,000259: # RE= RM FOR MOON
048548,000260: # RE= RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
048549,000261:
048550,000262: # CALLING SEQUENCE
048551,000263: # L CALL
048552,000264: # L+1 SETRE
048553,000265:
048554,000266: # SUBROUTINES USED
048555,000267: # GETERAD
048556,000268:
048557,000269: # INPUT
048558,000270: # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED RE
048559,000271: # ALPHAV +4= 1/2 SINL IF GETERAD IS CALLED
048560,000272: # LUNAFLAG=0 FOR EARTH,=1 FOR MOON
048561,000273:
048562,000274: # OUTPUT
048563,000275: # ERADM= 504RM FOR MOON (METERS B-29)
048564,000276: # ERADM= ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
048565,000277:
048566,000278: 13,2560 71220 SETRE STQ DLOAD
048567,000279: 13,2561 00051 SETREX
048568,000280: 13,2562 10003 504RM
048569,000281: 13,2563 71214 BON DLOAD # BRANCH FOR MOON
048570,000282: 13,2564 01703 LUNAFLAG
048571,000283: 13,2565 26575 TSTRLSRM
048572,000284: 13,2566 10001 ERAD
048573,000285: 13,2567 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
048574,000286: 13,2570 00742 ERADFLAG
048575,000287: 13,2571 26573 SETRXX
048576,000288: 13,2572 26466 GETERAD
048577,000289: 13,2573 37671 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
048578,000290: 13,2574 00051 SETREX
048579,000291: 13,2575 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
048580,000292: 13,2576 00702 ERADFLAG # =1 R0=RM
048581,000293: 13,2577 26573 SETRXX
048582,000294: 13,2600 02023 RLS
048583,000295: 13,2601 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
048584,000296: 13,2602 77650 GOTO
048585,000297: 13,2603 26573 SETRXX
048586,000298: 13,2604 0000051 SETREX = S2
048587,000299:
048588,000300:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc