Source Code
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These source-code files are part of a reconstructed copy of Luminary 97, the
original release of the Apollo 11 Lunar Module (LM) Apollo Guidance Computer
(AGC) software.
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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047393,000002: ## Copyright: Public domain.
047394,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
047395,000004: ## Purpose: A section of Luminary revision 97.
047396,000005: ## It is part of the reconstructed source code for the
047397,000006: ## original release of the flight software for the Lunar
047398,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
047399,000008: ## The code has been recreated from a copy of Luminary 99
047400,000009: ## revision 001, using asterisks indicating changed lines in
047401,000010: ## the listing and Luminary Memos #83 and #85, which list
047402,000011: ## changes between Luminary 97 and 98, and 98 and 99. The
047403,000012: ## code has been adapted such that the resulting bugger words
047404,000013: ## exactly match those specified for Luminary 97 in NASA drawing
047405,000014: ## 2021152D, which gives relatively high confidence that the
047406,000015: ## reconstruction is correct.
047407,000016: ## Reference: pp. 1133-1139
047408,000017: ## Assembler: yaYUL
047409,000018: ## Contact: Ron Burkey <info@sandroid.org>.
047410,000019: ## Website: www.ibiblio.org/apollo/index.html
047411,000020: ## Mod history: 2019-07-28 MAS Created from Luminary 99.
047412,000021:
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Page 1133
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047414,000023: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047415,000024:
047416,000025: # CALLING SEQUENCE
047417,000026: # L-1 CALL
047418,000027: # L LAT-LONG
047419,000028:
047420,000029: # SUBROUTINES USED
047421,000030: # R-TO-RP, ARCTAN, SETGAMMA, SETRE
047422,000031:
047423,000032: # ERASABLE INIT. REQ.
047424,000033: # AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
047425,000034: # ALPHAV = POSITION VECTOR METERS B-29
047426,000035: # MPAC -- TIME (CSECS B-28)
047427,000036: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047428,000037: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047429,000038:
047430,000039: # OUTPUT
047431,000040: # LATITUDE IN LAT (REVS. B-0)
047432,000041: # LONGITUDE IN LONG (REVS. B-0)
047433,000042: # ALTITUDE IN ALT METERS B-29
047434,000043:
047435,000044: 30,3775 BANK 30
047436,000045: 13,2000 SETLOC LATLONG
047437,000046: 13,2000 BANK
047438,000047:
047439,000048: 13,2351 COUNT* $$/LT-LG
047440,000049: 13,2351 E4,1431 EBANK= ALPHAV
047441,000050: 13,2351 40220 LAT-LONG STQ SETPD
047442,000051: 13,2352 03674 INCORPEX
047443,000052: 13,2353 00001 0D
047444,000053: 13,2354 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
047445,000054: 13,2355 02032 ALPHAV
047446,000055: 13,2356 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
047447,000056: 13,2357 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
047448,000057: 13,2360 24007 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047449,000058: 13,2361 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
047450,000059: 13,2362 01743 LUNAFLAG # 0=EARTH, 1=MOON
047451,000060: 13,2363 26364 CALLRTRP
047452,000061: 13,2364 77624 CALLRTRP CALL
047453,000062: 13,2365 51670 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
047454,000063: 13,2366 77656 UNIT # UNIT RP B-1
047455,000064: 13,2367 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
047456,000065: 13,2370 26550 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
047457,000066: 13,2371 77624 CALL # SCALED B-1
047458,000067: 13,2372 26560 SETRE # CALC RE METERS B-29
047459,000068: 13,2373 63545 DLOAD DSQ
047460,000069: 13,2374 02032 ALPHAV
047461,000070: 13,2375 63525 PDDL DSQ
047462,000071: 13,2376 02034 ALPHAV +2
047463,000072: 13,2377 75415 DAD SQRT
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Page 1134
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047465,000074: 13,2400 76405 DMP SL1R
047466,000075: 13,2401 00011 GAMRP
047467,000076: 13,2402 14021 STODL COSTH # COS(LAT) B-1
047468,000077: 13,2403 02036 ALPHAV +4
047469,000078: 13,2404 34023 STCALL SINTH # SIN(LAT) B-1
047470,000079: 13,2405 26510 ARCTAN
047471,000080: 13,2406 15121 STODL LAT # LAT B0
047472,000081: 13,2407 02032 ALPHAV
047473,000082: 13,2410 14021 STODL COSTH # COS(LONG) B-1
047474,000083: 13,2411 02034 ALPHAV +2
047475,000084: 13,2412 34023 STCALL SINTH # SIN(LONG) B-1
047476,000085: 13,2413 26510 ARCTAN
047477,000086: 13,2414 15123 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047478,000087: 13,2415 02070 ALPHAM
047479,000088: 13,2416 77625 DSU # ALT= R-RE METERS B-29
047480,000089: 13,2417 03673 ERADM
047481,000090: 13,2420 35125 STCALL ALT # EXIT WITH ALT METERS B-29
047482,000091: 13,2421 03674 INCORPEX
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Page 1135
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047484,000093: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047485,000094:
047486,000095: # CALLING SEQUENCE
047487,000096: # L-1 CALL
047488,000097: # L LALOTORV
047489,000098:
047490,000099: # SUBROUTINES USED
047491,000100: # SETGAMMA, SETRE, RP-TO-R
047492,000101:
047493,000102: # ERASABLE INIT. REQ.
047494,000103: # AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
047495,000104: # LAT -- LATITUDE (REVS B0)
047496,000105: # LONG -- LONGITUDE (REVS B0)
047497,000106: # ALT -- ALTITUDE (METERS) B-29
047498,000107: # MPAC -- TIME (CSECS B-28)
047499,000108: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047500,000109: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047501,000110:
047502,000111: # OUTPUT
047503,000112: # R-VECTOR IN ALPHAV (METERS B-29)
047504,000113:
047505,000114: 13,2422 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
047506,000115: 13,2423 03674 INCORPEX
047507,000116: 13,2424 00001 0D
047508,000117: 13,2425 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
047509,000118: 13,2426 26550 SETGAMMA # GAMMA=B2/A2 FOR EARTH, 1 FOR MOON B-1
047510,000119: 13,2427 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
047511,000120: 13,2430 01121 LAT # UNIT RP = SIN(LONG)COS(LAT) 2-3D
047512,000121: 13,2431 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
047513,000122: 13,2432 00011 GAMRP
047514,000123: 13,2433 01121 LAT # 0-1D = GAMMA*SIN(LAT) B-2
047515,000124: 13,2434 65346 COS PDDL # PD4 2-3D = COS(LAT) B-1 TEMPORARILY
047516,000125: 13,2435 01123 LONG
047517,000126: 13,2436 57356 SIN DMPR # PD 2
047518,000127: 13,2437 71525 PDDL COS # PD 4 2-3D = SIN(LONG)COS(LAT) B-2
047519,000128: 13,2440 01121 LAT
047520,000129: 13,2441 71525 PDDL COS # PD 6 4-5D = COS(LAT) B-1 TEMPORARILY
047521,000130: 13,2442 01123 LONG
047522,000131: 13,2443 55475 DMPR VDEF # PD 4 MPAC = COS(LONG)COS(LAT) B-2
047523,000132: 13,2444 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
047524,000133: 13,2445 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
047525,000134: 13,2446 26560 SETRE # RE METERS B-29
047526,000135: 13,2447 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047527,000136: 13,2450 24007 ZEROVEC
047528,000137: 13,2451 01743 LUNAFLAG
047529,000138: 13,2452 26454 CALLRPRT
047530,000139: 13,2453 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
047531,000140: 13,2454 77624 CALLRPRT CALL
047532,000141: 13,2455 55716 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
047533,000142: 13,2456 16032 STODL ALPHAV
047534,000143: 13,2457 03673 ERADM
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Page 1136
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047536,000145: 13,2460 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
047537,000146: 13,2461 01125 ALT
047538,000147: 13,2462 02032 ALPHAV
047539,000148: 13,2463 77772 VSL1 # R METERS B-29
047540,000149: 13,2464 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
047541,000150: 13,2465 03674 INCORPEX
047542,000151:
047543,000152: # SUBROUTINE TO COMPUTE EARTH RADIUS
047544,000153:
047545,000154: # INPUT
047546,000155: # 1/2 SIN LAT IN ALPHAV +4
047547,000156:
047548,000157: # OUTPUT
047549,000158: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047550,000159:
047551,000160: 13,2466 63545 GETERAD DLOAD DSQ
047552,000161: 13,2467 02036 ALPHAV +4 # SIN**2(L)
047553,000162: 13,2470 44352 SL1 BDSU
047554,000163: 13,2471 24005 DP1/2 # COS**2(L)
047555,000164: 13,2472 44275 DMPR BDSU
047556,000165: 13,2473 26507 EE
047557,000166: 13,2474 24005 DP1/2
047558,000167: 13,2475 75465 BDDV SQRT
047559,000168: 13,2476 26503 B2XSC
047560,000169: 13,2477 77622 SR4R
047561,000170: 13,2500 03673 STORE ERADM
047562,000171: 13,2501 77616 RVQ
047563,000172:
047564,000173: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
047565,000174: # B2XSC = B**2 SCALED B-51
047566,000175: # B2/A2 = B**2/A**2 SCALED B-1
047567,000176: # EE = (1-B**2/A**2) SCALED B-0
047568,000177:
047569,000178: 13,2502 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
047570,000179: 13,2504 12,2004 DP1/2 = XUNIT
047571,000180: 13,2504 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
047572,000181: 13,2506 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
047573,000182:
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Page 1137
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047575,000184: # ARCTAN SUBROUTINE
047576,000185:
047577,000186: # CALLING SEQUENCE
047578,000187: # SIN THETA IN SINTH B-1
047579,000188: # COS THETA IN COSTH B-1
047580,000189: # CALL ARCTAN
047581,000190:
047582,000191: # OUTPUT
047583,000192: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047584,000193:
047585,000194: 13,2510 77600 ARCTAN BOV
047586,000195: 13,2511 26512 CLROVFLW
047587,000196: 13,2512 63545 CLROVFLW DLOAD DSQ
047588,000197: 13,2513 00023 SINTH
047589,000198: 13,2514 63525 PDDL DSQ
047590,000199: 13,2515 00021 COSTH
047591,000200: 13,2516 77615 DAD
047592,000201: 13,2517 75454 BZE SQRT
047593,000202: 13,2520 26536 ARCTANXX # ATAN=0/0 SET THETA=0
047594,000203: 13,2521 40065 BDDV BOV
047595,000204: 13,2522 00023 SINTH
047596,000205: 13,2523 26543 ATAN=90
047597,000206: 13,2524 67542 SR1 ASIN
047598,000207: 13,2525 00025 STORE THETA
047599,000208: 13,2526 50125 PDDL BMN
047600,000209: 13,2527 00021 COSTH
047601,000210: 13,2530 26532 NEGCOS
047602,000211: 13,2531 43545 DLOAD RVQ
047603,000212: 13,2532 57545 NEGCOS DLOAD DCOMP
047604,000213: 13,2533 43244 BPL DAD
047605,000214: 13,2534 26540 NEGOUT
047606,000215: 13,2535 24005 DP1/2
047607,000216: 13,2536 00025 ARCTANXX STORE THETA
047608,000217: 13,2537 77616 RVQ
047609,000218:
047610,000219: 13,2540 52025 NEGOUT DSU GOTO
047611,000220: 13,2541 24005 DP1/2
047612,000221: 13,2542 26536 ARCTANXX
047613,000222: 13,2543 75345 ATAN=90 DLOAD SIGN
047614,000223: 13,2544 11037 LODP1/4
047615,000224: 13,2545 00023 SINTH
047616,000225: 13,2546 00025 STORE THETA
047617,000226: 13,2547 77616 RVQ
047618,000227:
047619,000228: 13,2550 12,2006 2DZERO = DPZERO
047620,000229:
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Page 1138
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047622,000231: # ..... SETGAMMA SUBROUTINE .....
047623,000232: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047624,000233:
047625,000234: # GAMMA = B**2/A**2 FOR EARTH (B-1)
047626,000235: # GAMMA = 1 FOR MOON (B-1)
047627,000236:
047628,000237: # CALLING SEQUENCE
047629,000238: # L CALL
047630,000239: # L+1 SETGAMMA
047631,000240:
047632,000241: # INPUT
047633,000242: # LUNAFLAG=0 FOR EARTH, =1 FOR MOON
047634,000243:
047635,000244: # OUTPUT
047636,000245: # GAMMA IN GAMRP (B-1)
047637,000246:
047638,000247: 13,2550 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
047639,000248: 13,2551 26505 B2/A2 # EARTH GAMMA
047640,000249: 13,2552 01743 LUNAFLAG
047641,000250: 13,2553 26556 SETGMEX
047642,000251: 13,2554 77735 SLOAD
047643,000252: 13,2555 24005 1B1 # MOON GAMMA
047644,000253: 13,2556 00011 SETGMEX STORE GAMRP
047645,000254: 13,2557 77616 RVQ
047646,000255: 13,2560 GAMRP = 8D
047647,000256:
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Page 1139
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047649,000258: # ..... SETRE SUBROUTINE .....
047650,000259: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047651,000260:
047652,000261: # RE = RM FOR MOON
047653,000262: # RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047654,000263:
047655,000264: # CALLING SEQUENCE
047656,000265: # L CALL
047657,000266: # L+1 SETRE
047658,000267:
047659,000268: # SUBROUTINES USED
047660,000269: # GETERAD
047661,000270:
047662,000271: # INPUT
047663,000272: # ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
047664,000273: # ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
047665,000274: # LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
047666,000275:
047667,000276: # OUTPUT
047668,000277: # ERADM = 504RM FOR MOON (METERS B-29)
047669,000278: # ERADM = ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047670,000279:
047671,000280: 13,2560 71220 SETRE STQ DLOAD
047672,000281: 13,2561 00051 SETREX
047673,000282: 13,2562 10003 504RM
047674,000283: 13,2563 71214 BON DLOAD # BRANCH FOR MOON
047675,000284: 13,2564 01703 LUNAFLAG
047676,000285: 13,2565 26575 TSTRLSRM
047677,000286: 13,2566 10001 ERAD
047678,000287: 13,2567 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
047679,000288: 13,2570 00742 ERADFLAG
047680,000289: 13,2571 26573 SETRXX
047681,000290: 13,2572 26466 GETERAD
047682,000291: 13,2573 37673 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
047683,000292: 13,2574 00051 SETREX
047684,000293: 13,2575 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
047685,000294: 13,2576 00702 ERADFLAG # =1 R0=RM
047686,000295: 13,2577 26573 SETRXX
047687,000296: 13,2600 02023 RLS
047688,000297: 13,2601 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
047689,000298: 13,2602 77650 GOTO
047690,000299: 13,2603 26573 SETRXX
047691,000300: 13,2604 0000051 SETREX = S2
047692,000301:
047693,000302:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc