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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047530,000002: ## Copyright: Public domain.
047531,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
047532,000004: ## Purpose: A section of Luminary revision 97.
047533,000005: ## It is part of the reconstructed source code for the
047534,000006: ## second release of the flight software for the Lunar
047535,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
047536,000008: ## It was created to fix two incorrect ephemeris constants in
047537,000009: ## Luminary 96, as described by anomaly report LNY-59.
047538,000010: ## The code has been recreated from a copy of Luminary 99
047539,000011: ## revision 001, using asterisks indicating changed lines in
047540,000012: ## the listing and Luminary Memos #83 and #85, which list
047541,000013: ## changes between Luminary 97 and 98, and 98 and 99. The
047542,000014: ## code has been adapted such that the resulting bugger words
047543,000015: ## exactly match those specified for Luminary 97 in NASA drawing
047544,000016: ## 2021152D, which gives relatively high confidence that the
047545,000017: ## reconstruction is correct.
047546,000018: ## Reference: pp. 1133-1139
047547,000019: ## Assembler: yaYUL
047548,000020: ## Contact: Ron Burkey <info@sandroid.org>.
047549,000021: ## Website: www.ibiblio.org/apollo/index.html
047550,000022: ## Mod history: 2019-07-28 MAS Created from Luminary 99.
047551,000023:
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Page 1133
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047553,000025: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047554,000026:
047555,000027: # CALLING SEQUENCE
047556,000028: # L-1 CALL
047557,000029: # L LAT-LONG
047558,000030:
047559,000031: # SUBROUTINES USED
047560,000032: # R-TO-RP, ARCTAN, SETGAMMA, SETRE
047561,000033:
047562,000034: # ERASABLE INIT. REQ.
047563,000035: # AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
047564,000036: # ALPHAV = POSITION VECTOR METERS B-29
047565,000037: # MPAC -- TIME (CSECS B-28)
047566,000038: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047567,000039: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047568,000040:
047569,000041: # OUTPUT
047570,000042: # LATITUDE IN LAT (REVS. B-0)
047571,000043: # LONGITUDE IN LONG (REVS. B-0)
047572,000044: # ALTITUDE IN ALT METERS B-29
047573,000045:
047574,000046: 30,3775 BANK 30
047575,000047: 13,2000 SETLOC LATLONG
047576,000048: 13,2000 BANK
047577,000049:
047578,000050: 13,2351 COUNT* $$/LT-LG
047579,000051: 13,2351 E4,1431 EBANK= ALPHAV
047580,000052: 13,2351 40220 LAT-LONG STQ SETPD
047581,000053: 13,2352 03674 INCORPEX
047582,000054: 13,2353 00001 0D
047583,000055: 13,2354 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
047584,000056: 13,2355 02032 ALPHAV
047585,000057: 13,2356 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
047586,000058: 13,2357 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
047587,000059: 13,2360 24007 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047588,000060: 13,2361 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
047589,000061: 13,2362 01743 LUNAFLAG # 0=EARTH, 1=MOON
047590,000062: 13,2363 26364 CALLRTRP
047591,000063: 13,2364 77624 CALLRTRP CALL
047592,000064: 13,2365 51670 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
047593,000065: 13,2366 77656 UNIT # UNIT RP B-1
047594,000066: 13,2367 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
047595,000067: 13,2370 26550 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
047596,000068: 13,2371 77624 CALL # SCALED B-1
047597,000069: 13,2372 26560 SETRE # CALC RE METERS B-29
047598,000070: 13,2373 63545 DLOAD DSQ
047599,000071: 13,2374 02032 ALPHAV
047600,000072: 13,2375 63525 PDDL DSQ
047601,000073: 13,2376 02034 ALPHAV +2
047602,000074: 13,2377 75415 DAD SQRT
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Page 1134
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047604,000076: 13,2400 76405 DMP SL1R
047605,000077: 13,2401 00011 GAMRP
047606,000078: 13,2402 14021 STODL COSTH # COS(LAT) B-1
047607,000079: 13,2403 02036 ALPHAV +4
047608,000080: 13,2404 34023 STCALL SINTH # SIN(LAT) B-1
047609,000081: 13,2405 26510 ARCTAN
047610,000082: 13,2406 15121 STODL LAT # LAT B0
047611,000083: 13,2407 02032 ALPHAV
047612,000084: 13,2410 14021 STODL COSTH # COS(LONG) B-1
047613,000085: 13,2411 02034 ALPHAV +2
047614,000086: 13,2412 34023 STCALL SINTH # SIN(LONG) B-1
047615,000087: 13,2413 26510 ARCTAN
047616,000088: 13,2414 15123 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047617,000089: 13,2415 02070 ALPHAM
047618,000090: 13,2416 77625 DSU # ALT= R-RE METERS B-29
047619,000091: 13,2417 03673 ERADM
047620,000092: 13,2420 35125 STCALL ALT # EXIT WITH ALT METERS B-29
047621,000093: 13,2421 03674 INCORPEX
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Page 1135
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047623,000095: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047624,000096:
047625,000097: # CALLING SEQUENCE
047626,000098: # L-1 CALL
047627,000099: # L LALOTORV
047628,000100:
047629,000101: # SUBROUTINES USED
047630,000102: # SETGAMMA, SETRE, RP-TO-R
047631,000103:
047632,000104: # ERASABLE INIT. REQ.
047633,000105: # AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
047634,000106: # LAT -- LATITUDE (REVS B0)
047635,000107: # LONG -- LONGITUDE (REVS B0)
047636,000108: # ALT -- ALTITUDE (METERS) B-29
047637,000109: # MPAC -- TIME (CSECS B-28)
047638,000110: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047639,000111: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047640,000112:
047641,000113: # OUTPUT
047642,000114: # R-VECTOR IN ALPHAV (METERS B-29)
047643,000115:
047644,000116: 13,2422 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
047645,000117: 13,2423 03674 INCORPEX
047646,000118: 13,2424 00001 0D
047647,000119: 13,2425 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
047648,000120: 13,2426 26550 SETGAMMA # GAMMA=B2/A2 FOR EARTH, 1 FOR MOON B-1
047649,000121: 13,2427 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
047650,000122: 13,2430 01121 LAT # UNIT RP = SIN(LONG)COS(LAT) 2-3D
047651,000123: 13,2431 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
047652,000124: 13,2432 00011 GAMRP
047653,000125: 13,2433 01121 LAT # 0-1D = GAMMA*SIN(LAT) B-2
047654,000126: 13,2434 65346 COS PDDL # PD4 2-3D = COS(LAT) B-1 TEMPORARILY
047655,000127: 13,2435 01123 LONG
047656,000128: 13,2436 57356 SIN DMPR # PD 2
047657,000129: 13,2437 71525 PDDL COS # PD 4 2-3D = SIN(LONG)COS(LAT) B-2
047658,000130: 13,2440 01121 LAT
047659,000131: 13,2441 71525 PDDL COS # PD 6 4-5D = COS(LAT) B-1 TEMPORARILY
047660,000132: 13,2442 01123 LONG
047661,000133: 13,2443 55475 DMPR VDEF # PD 4 MPAC = COS(LONG)COS(LAT) B-2
047662,000134: 13,2444 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
047663,000135: 13,2445 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
047664,000136: 13,2446 26560 SETRE # RE METERS B-29
047665,000137: 13,2447 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047666,000138: 13,2450 24007 ZEROVEC
047667,000139: 13,2451 01743 LUNAFLAG
047668,000140: 13,2452 26454 CALLRPRT
047669,000141: 13,2453 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
047670,000142: 13,2454 77624 CALLRPRT CALL
047671,000143: 13,2455 55716 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
047672,000144: 13,2456 16032 STODL ALPHAV
047673,000145: 13,2457 03673 ERADM
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Page 1136
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047675,000147: 13,2460 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
047676,000148: 13,2461 01125 ALT
047677,000149: 13,2462 02032 ALPHAV
047678,000150: 13,2463 77772 VSL1 # R METERS B-29
047679,000151: 13,2464 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
047680,000152: 13,2465 03674 INCORPEX
047681,000153:
047682,000154: # SUBROUTINE TO COMPUTE EARTH RADIUS
047683,000155:
047684,000156: # INPUT
047685,000157: # 1/2 SIN LAT IN ALPHAV +4
047686,000158:
047687,000159: # OUTPUT
047688,000160: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047689,000161:
047690,000162: 13,2466 63545 GETERAD DLOAD DSQ
047691,000163: 13,2467 02036 ALPHAV +4 # SIN**2(L)
047692,000164: 13,2470 44352 SL1 BDSU
047693,000165: 13,2471 24005 DP1/2 # COS**2(L)
047694,000166: 13,2472 44275 DMPR BDSU
047695,000167: 13,2473 26507 EE
047696,000168: 13,2474 24005 DP1/2
047697,000169: 13,2475 75465 BDDV SQRT
047698,000170: 13,2476 26503 B2XSC
047699,000171: 13,2477 77622 SR4R
047700,000172: 13,2500 03673 STORE ERADM
047701,000173: 13,2501 77616 RVQ
047702,000174:
047703,000175: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
047704,000176: # B2XSC = B**2 SCALED B-51
047705,000177: # B2/A2 = B**2/A**2 SCALED B-1
047706,000178: # EE = (1-B**2/A**2) SCALED B-0
047707,000179:
047708,000180: 13,2502 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
047709,000181: 13,2504 12,2004 DP1/2 = XUNIT
047710,000182: 13,2504 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
047711,000183: 13,2506 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
047712,000184:
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Page 1137
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047714,000186: # ARCTAN SUBROUTINE
047715,000187:
047716,000188: # CALLING SEQUENCE
047717,000189: # SIN THETA IN SINTH B-1
047718,000190: # COS THETA IN COSTH B-1
047719,000191: # CALL ARCTAN
047720,000192:
047721,000193: # OUTPUT
047722,000194: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047723,000195:
047724,000196: 13,2510 77600 ARCTAN BOV
047725,000197: 13,2511 26512 CLROVFLW
047726,000198: 13,2512 63545 CLROVFLW DLOAD DSQ
047727,000199: 13,2513 00023 SINTH
047728,000200: 13,2514 63525 PDDL DSQ
047729,000201: 13,2515 00021 COSTH
047730,000202: 13,2516 77615 DAD
047731,000203: 13,2517 75454 BZE SQRT
047732,000204: 13,2520 26536 ARCTANXX # ATAN=0/0 SET THETA=0
047733,000205: 13,2521 40065 BDDV BOV
047734,000206: 13,2522 00023 SINTH
047735,000207: 13,2523 26543 ATAN=90
047736,000208: 13,2524 67542 SR1 ASIN
047737,000209: 13,2525 00025 STORE THETA
047738,000210: 13,2526 50125 PDDL BMN
047739,000211: 13,2527 00021 COSTH
047740,000212: 13,2530 26532 NEGCOS
047741,000213: 13,2531 43545 DLOAD RVQ
047742,000214: 13,2532 57545 NEGCOS DLOAD DCOMP
047743,000215: 13,2533 43244 BPL DAD
047744,000216: 13,2534 26540 NEGOUT
047745,000217: 13,2535 24005 DP1/2
047746,000218: 13,2536 00025 ARCTANXX STORE THETA
047747,000219: 13,2537 77616 RVQ
047748,000220:
047749,000221: 13,2540 52025 NEGOUT DSU GOTO
047750,000222: 13,2541 24005 DP1/2
047751,000223: 13,2542 26536 ARCTANXX
047752,000224: 13,2543 75345 ATAN=90 DLOAD SIGN
047753,000225: 13,2544 11037 LODP1/4
047754,000226: 13,2545 00023 SINTH
047755,000227: 13,2546 00025 STORE THETA
047756,000228: 13,2547 77616 RVQ
047757,000229:
047758,000230: 13,2550 12,2006 2DZERO = DPZERO
047759,000231:
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Page 1138
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047761,000233: # ..... SETGAMMA SUBROUTINE .....
047762,000234: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047763,000235:
047764,000236: # GAMMA = B**2/A**2 FOR EARTH (B-1)
047765,000237: # GAMMA = 1 FOR MOON (B-1)
047766,000238:
047767,000239: # CALLING SEQUENCE
047768,000240: # L CALL
047769,000241: # L+1 SETGAMMA
047770,000242:
047771,000243: # INPUT
047772,000244: # LUNAFLAG=0 FOR EARTH, =1 FOR MOON
047773,000245:
047774,000246: # OUTPUT
047775,000247: # GAMMA IN GAMRP (B-1)
047776,000248:
047777,000249: 13,2550 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
047778,000250: 13,2551 26505 B2/A2 # EARTH GAMMA
047779,000251: 13,2552 01743 LUNAFLAG
047780,000252: 13,2553 26556 SETGMEX
047781,000253: 13,2554 77735 SLOAD
047782,000254: 13,2555 24005 1B1 # MOON GAMMA
047783,000255: 13,2556 00011 SETGMEX STORE GAMRP
047784,000256: 13,2557 77616 RVQ
047785,000257: 13,2560 GAMRP = 8D
047786,000258:
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Page 1139
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047788,000260: # ..... SETRE SUBROUTINE .....
047789,000261: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047790,000262:
047791,000263: # RE = RM FOR MOON
047792,000264: # RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047793,000265:
047794,000266: # CALLING SEQUENCE
047795,000267: # L CALL
047796,000268: # L+1 SETRE
047797,000269:
047798,000270: # SUBROUTINES USED
047799,000271: # GETERAD
047800,000272:
047801,000273: # INPUT
047802,000274: # ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
047803,000275: # ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
047804,000276: # LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
047805,000277:
047806,000278: # OUTPUT
047807,000279: # ERADM = 504RM FOR MOON (METERS B-29)
047808,000280: # ERADM = ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047809,000281:
047810,000282: 13,2560 71220 SETRE STQ DLOAD
047811,000283: 13,2561 00051 SETREX
047812,000284: 13,2562 10003 504RM
047813,000285: 13,2563 71214 BON DLOAD # BRANCH FOR MOON
047814,000286: 13,2564 01703 LUNAFLAG
047815,000287: 13,2565 26575 TSTRLSRM
047816,000288: 13,2566 10001 ERAD
047817,000289: 13,2567 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
047818,000290: 13,2570 00742 ERADFLAG
047819,000291: 13,2571 26573 SETRXX
047820,000292: 13,2572 26466 GETERAD
047821,000293: 13,2573 37673 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
047822,000294: 13,2574 00051 SETREX
047823,000295: 13,2575 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
047824,000296: 13,2576 00702 ERADFLAG # =1 R0=RM
047825,000297: 13,2577 26573 SETRXX
047826,000298: 13,2600 02023 RLS
047827,000299: 13,2601 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
047828,000300: 13,2602 77650 GOTO
047829,000301: 13,2603 26573 SETRXX
047830,000302: 13,2604 0000051 SETREX = S2
047831,000303:
047832,000304:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc