Source Code
![]() |
This is an attempt to recreate Luminary 99 Rev 2, otherwise known as LUM99R2, from Luminary 99 Rev 1 and ephemeris data from Luminary 116. The differences are confined to the last 10-12 lines of the CONTROLLED CONSTANTS. Luminary 99 Rev 1 source-code was transcribed from a printout in the MIT Museum, while Luminary 116 source code was transcribed from a printout belonging to Don Eyles. AGC developer James Kernan, the "rope mother" for the Apollo 11 Lunar Module's AGC, explains as follows: "At the last minute, Dan Lickly, our chief engineer, appeared with ephemerides updates and it took two tries to get it right. The result was that we created Lum99 Revision 1 and Lum99 Revision 2." It is suspected that the former is what's in the MIT Museum, and the latter is what we are trying to recreate here. As for which revision actually flew in Apollo 11, all of the other available surviving evidence points to Rev 1 rather than to Rev 2, so we're just not sure! |
047419,000002: ## Copyright: Public domain.
047420,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
047421,000004: ## Purpose: Part of the source code for Luminary 1A build 099.
047422,000005: ## It is part of the source code for the Lunar Module's (LM)
047423,000006: ## Apollo Guidance Computer (AGC), for Apollo 11.
047424,000007: ##
047425,000008: ## Assembler: yaYUL
047426,000009: ## Contact: Jim Lawton <jim DOT lawton AT gmail DOT com>
047427,000010: ## Website: www.ibiblio.org/apollo.
047428,000011: ## Pages: 1133-1139
047429,000012: ## Mod history: 2009-05-28 JL Updated from page images.
047430,000013: ## 2011-01-06 JL Fixed interpretive indentation.
047431,000014: ## 2016-12-17 RSB Proofed text comments with octopus/ProoferComments
047432,000015: ## and corrected the errors found.
047433,000016: ## 2017-03-03 RSB Snapshot of Luminary 99 Rev 1.
047434,000017: ## 2017-03-15 RSB Comment-text fixes identified in 5-way
047435,000018: ## side-by-side diff of Luminary 69/99/116/131/210.
047436,000019:
![]() |
Page 1133 |
047438,000021: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047439,000022:
047440,000023: # CALLING SEQUENCE
047441,000024: # L-1 CALL
047442,000025: # L LAT-LONG
047443,000026:
047444,000027: # SUBROUTINES USED
047445,000028: # R-TO-RP, ARCTAN, SETGAMMA, SETRE
047446,000029:
047447,000030: # ERASABLE INIT. REQ.
047448,000031: # AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
047449,000032: # ALPHAV = POSITION VECTOR METERS B-29
047450,000033: # MPAC -- TIME (CSECS B-28)
047451,000034: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047452,000035: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047453,000036:
047454,000037: # OUTPUT
047455,000038: # LATITUDE IN LAT (REVS. B-0)
047456,000039: # LONGITUDE IN LONG (REVS. B-0)
047457,000040: # ALTITUDE IN ALT METERS B-29
047458,000041:
047459,000042: 30,3775 BANK 30
047460,000043: 13,2000 SETLOC LATLONG
047461,000044: 13,2000 BANK
047462,000045:
047463,000046: 13,2351 COUNT* $$/LT-LG
047464,000047: 13,2351 E4,1431 EBANK= ALPHAV
047465,000048: 13,2351 40220 LAT-LONG STQ SETPD
047466,000049: 13,2352 03674 INCORPEX
047467,000050: 13,2353 00001 0D
047468,000051: 13,2354 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
047469,000052: 13,2355 02032 ALPHAV
047470,000053: 13,2356 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
047471,000054: 13,2357 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
047472,000055: 13,2360 24007 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047473,000056: 13,2361 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
047474,000057: 13,2362 01743 LUNAFLAG # 0=EARTH, 1=MOON
047475,000058: 13,2363 26364 CALLRTRP
047476,000059: 13,2364 77624 CALLRTRP CALL
047477,000060: 13,2365 51670 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
047478,000061: 13,2366 77656 UNIT # UNIT RP B-1
047479,000062: 13,2367 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
047480,000063: 13,2370 26550 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
047481,000064: 13,2371 77624 CALL # SCALED B-1
047482,000065: 13,2372 26560 SETRE # CALC RE METERS B-29
047483,000066: 13,2373 63545 DLOAD DSQ
047484,000067: 13,2374 02032 ALPHAV
047485,000068: 13,2375 63525 PDDL DSQ
047486,000069: 13,2376 02034 ALPHAV +2
047487,000070: 13,2377 75415 DAD SQRT
![]() |
Page 1134 |
047489,000072: 13,2400 76405 DMP SL1R
047490,000073: 13,2401 00011 GAMRP
047491,000074: 13,2402 14021 STODL COSTH # COS(LAT) B-1
047492,000075: 13,2403 02036 ALPHAV +4
047493,000076: 13,2404 34023 STCALL SINTH # SIN(LAT) B-1
047494,000077: 13,2405 26510 ARCTAN
047495,000078: 13,2406 15121 STODL LAT # LAT B0
047496,000079: 13,2407 02032 ALPHAV
047497,000080: 13,2410 14021 STODL COSTH # COS(LONG) B-1
047498,000081: 13,2411 02034 ALPHAV +2
047499,000082: 13,2412 34023 STCALL SINTH # SIN(LONG) B-1
047500,000083: 13,2413 26510 ARCTAN
047501,000084: 13,2414 15123 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047502,000085: 13,2415 02070 ALPHAM
047503,000086: 13,2416 77625 DSU # ALT= R-RE METERS B-29
047504,000087: 13,2417 03673 ERADM
047505,000088: 13,2420 35125 STCALL ALT # EXIT WITH ALT METERS B-29
047506,000089: 13,2421 03674 INCORPEX
![]() |
Page 1135 |
047508,000091: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047509,000092:
047510,000093: # CALLING SEQUENCE
047511,000094: # L-1 CALL
047512,000095: # L LALOTORV
047513,000096:
047514,000097: # SUBROUTINES USED
047515,000098: # SETGAMMA, SETRE, RP-TO-R
047516,000099:
047517,000100: # ERASABLE INIT. REQ.
047518,000101: # AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
047519,000102: # LAT -- LATITUDE (REVS B0)
047520,000103: # LONG -- LONGITUDE (REVS B0)
047521,000104: # ALT -- ALTITUDE (METERS) B-29
047522,000105: # MPAC -- TIME (CSECS B-28)
047523,000106: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047524,000107: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047525,000108:
047526,000109: # OUTPUT
047527,000110: # R-VECTOR IN ALPHAV (METERS B-29)
047528,000111:
047529,000112: 13,2422 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
047530,000113: 13,2423 03674 INCORPEX
047531,000114: 13,2424 00001 0D
047532,000115: 13,2425 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
047533,000116: 13,2426 26550 SETGAMMA # GAMMA=B2/A2 FOR EARTH, 1 FOR MOON B-1
047534,000117: 13,2427 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
047535,000118: 13,2430 01121 LAT # UNIT RP = SIN(LONG)COS(LAT) 2-3D
047536,000119: 13,2431 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
047537,000120: 13,2432 00011 GAMRP
047538,000121: 13,2433 01121 LAT # 0-1D = GAMMA*SIN(LAT) B-2
047539,000122: 13,2434 65346 COS PDDL # PD4 2-3D = COS(LAT) B-1 TEMPORARILY
047540,000123: 13,2435 01123 LONG
047541,000124: 13,2436 57356 SIN DMPR # PD 2
047542,000125: 13,2437 71525 PDDL COS # PD 4 2-3D = SIN(LONG)COS(LAT) B-2
047543,000126: 13,2440 01121 LAT
047544,000127: 13,2441 71525 PDDL COS # PD 6 4-5D = COS(LAT) B-1 TEMPORARILY
047545,000128: 13,2442 01123 LONG
047546,000129: 13,2443 55475 DMPR VDEF # PD 4 MPAC = COS(LONG)COS(LAT) B-2
047547,000130: 13,2444 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
047548,000131: 13,2445 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
047549,000132: 13,2446 26560 SETRE # RE METERS B-29
047550,000133: 13,2447 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047551,000134: 13,2450 24007 ZEROVEC
047552,000135: 13,2451 01743 LUNAFLAG
047553,000136: 13,2452 26454 CALLRPRT
047554,000137: 13,2453 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
047555,000138: 13,2454 77624 CALLRPRT CALL
047556,000139: 13,2455 55716 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
047557,000140: 13,2456 16032 STODL ALPHAV
047558,000141: 13,2457 03673 ERADM
![]() |
Page 1136 |
047560,000143: 13,2460 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
047561,000144: 13,2461 01125 ALT
047562,000145: 13,2462 02032 ALPHAV
047563,000146: 13,2463 77772 VSL1 # R METERS B-29
047564,000147: 13,2464 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
047565,000148: 13,2465 03674 INCORPEX
047566,000149:
047567,000150: # SUBROUTINE TO COMPUTE EARTH RADIUS
047568,000151:
047569,000152: # INPUT
047570,000153: # 1/2 SIN LAT IN ALPHAV +4
047571,000154:
047572,000155: # OUTPUT
047573,000156: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047574,000157:
047575,000158: 13,2466 63545 GETERAD DLOAD DSQ
047576,000159: 13,2467 02036 ALPHAV +4 # SIN**2(L)
047577,000160: 13,2470 44352 SL1 BDSU
047578,000161: 13,2471 24005 DP1/2 # COS**2(L)
047579,000162: 13,2472 44275 DMPR BDSU
047580,000163: 13,2473 26507 EE
047581,000164: 13,2474 24005 DP1/2
047582,000165: 13,2475 75465 BDDV SQRT
047583,000166: 13,2476 26503 B2XSC
047584,000167: 13,2477 77622 SR4R
047585,000168: 13,2500 03673 STORE ERADM
047586,000169: 13,2501 77616 RVQ
047587,000170:
047588,000171: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
047589,000172: # B2XSC = B**2 SCALED B-51
047590,000173: # B2/A2 = B**2/A**2 SCALED B-1
047591,000174: # EE = (1-B**2/A**2) SCALED B-0
047592,000175:
047593,000176: 13,2502 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
047594,000177: 13,2504 12,2004 DP1/2 = XUNIT
047595,000178: 13,2504 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
047596,000179: 13,2506 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
047597,000180:
![]() |
Page 1137 |
047599,000182: # ARCTAN SUBROUTINE
047600,000183:
047601,000184: # CALLING SEQUENCE
047602,000185: # SIN THETA IN SINTH B-1
047603,000186: # COS THETA IN COSTH B-1
047604,000187: # CALL ARCTAN
047605,000188:
047606,000189: # OUTPUT
047607,000190: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047608,000191:
047609,000192: 13,2510 77600 ARCTAN BOV
047610,000193: 13,2511 26512 CLROVFLW
047611,000194: 13,2512 63545 CLROVFLW DLOAD DSQ
047612,000195: 13,2513 00023 SINTH
047613,000196: 13,2514 63525 PDDL DSQ
047614,000197: 13,2515 00021 COSTH
047615,000198: 13,2516 77615 DAD
047616,000199: 13,2517 75454 BZE SQRT
047617,000200: 13,2520 26536 ARCTANXX # ATAN=0/0 SET THETA=0
047618,000201: 13,2521 40065 BDDV BOV
047619,000202: 13,2522 00023 SINTH
047620,000203: 13,2523 26543 ATAN=90
047621,000204: 13,2524 67542 SR1 ASIN
047622,000205: 13,2525 00025 STORE THETA
047623,000206: 13,2526 50125 PDDL BMN
047624,000207: 13,2527 00021 COSTH
047625,000208: 13,2530 26532 NEGCOS
047626,000209: 13,2531 43545 DLOAD RVQ
047627,000210: 13,2532 57545 NEGCOS DLOAD DCOMP
047628,000211: 13,2533 43244 BPL DAD
047629,000212: 13,2534 26540 NEGOUT
047630,000213: 13,2535 24005 DP1/2
047631,000214: 13,2536 00025 ARCTANXX STORE THETA
047632,000215: 13,2537 77616 RVQ
047633,000216:
047634,000217: 13,2540 52025 NEGOUT DSU GOTO
047635,000218: 13,2541 24005 DP1/2
047636,000219: 13,2542 26536 ARCTANXX
047637,000220: 13,2543 75345 ATAN=90 DLOAD SIGN
047638,000221: 13,2544 11037 LODP1/4
047639,000222: 13,2545 00023 SINTH
047640,000223: 13,2546 00025 STORE THETA
047641,000224: 13,2547 77616 RVQ
047642,000225:
047643,000226: 13,2550 12,2006 2DZERO = DPZERO
047644,000227:
![]() |
Page 1138 |
047646,000229: # ..... SETGAMMA SUBROUTINE .....
047647,000230: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047648,000231:
047649,000232: # GAMMA = B**2/A**2 FOR EARTH (B-1)
047650,000233: # GAMMA = 1 FOR MOON (B-1)
047651,000234:
047652,000235: # CALLING SEQUENCE
047653,000236: # L CALL
047654,000237: # L+1 SETGAMMA
047655,000238:
047656,000239: # INPUT
047657,000240: # LUNAFLAG=0 FOR EARTH, =1 FOR MOON
047658,000241:
047659,000242: # OUTPUT
047660,000243: # GAMMA IN GAMRP (B-1)
047661,000244:
047662,000245: 13,2550 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
047663,000246: 13,2551 26505 B2/A2 # EARTH GAMMA
047664,000247: 13,2552 01743 LUNAFLAG
047665,000248: 13,2553 26556 SETGMEX
047666,000249: 13,2554 77735 SLOAD
047667,000250: 13,2555 24005 1B1 # MOON GAMMA
047668,000251: 13,2556 00011 SETGMEX STORE GAMRP
047669,000252: 13,2557 77616 RVQ
047670,000253: 13,2560 GAMRP = 8D
047671,000254:
![]() |
Page 1139 |
047673,000256: # ..... SETRE SUBROUTINE .....
047674,000257: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047675,000258:
047676,000259: # RE = RM FOR MOON
047677,000260: # RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047678,000261:
047679,000262: # CALLING SEQUENCE
047680,000263: # L CALL
047681,000264: # L+1 SETRE
047682,000265:
047683,000266: # SUBROUTINES USED
047684,000267: # GETERAD
047685,000268:
047686,000269: # INPUT
047687,000270: # ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
047688,000271: # ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
047689,000272: # LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
047690,000273:
047691,000274: # OUTPUT
047692,000275: # ERADM = 504RM FOR MOON (METERS B-29)
047693,000276: # ERADM = ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047694,000277:
047695,000278: 13,2560 71220 SETRE STQ DLOAD
047696,000279: 13,2561 00051 SETREX
047697,000280: 13,2562 10003 504RM
047698,000281: 13,2563 71214 BON DLOAD # BRANCH FOR MOON
047699,000282: 13,2564 01703 LUNAFLAG
047700,000283: 13,2565 26575 TSTRLSRM
047701,000284: 13,2566 10001 ERAD
047702,000285: 13,2567 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
047703,000286: 13,2570 00742 ERADFLAG
047704,000287: 13,2571 26573 SETRXX
047705,000288: 13,2572 26466 GETERAD
047706,000289: 13,2573 37673 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
047707,000290: 13,2574 00051 SETREX
047708,000291: 13,2575 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
047709,000292: 13,2576 00702 ERADFLAG # =1 R0=RM
047710,000293: 13,2577 26573 SETRXX
047711,000294: 13,2600 02023 RLS
047712,000295: 13,2601 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
047713,000296: 13,2602 77650 GOTO
047714,000297: 13,2603 26573 SETRXX
047715,000298: 13,2604 0000051 SETREX = S2
047716,000299:
047717,000300:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc