Source Code
053442,000001: # Copyright: Public domain.
053443,000002: # Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
053444,000003: # Purpose: Part of the source code for Colossus 2A, AKA Comanche 055.
053445,000004: # It is part of the source code for the Command Module's (CM)
053446,000005: # Apollo Guidance Computer (AGC), for Apollo 11.
053447,000006: # Assembler: yaYUL
053448,000007: # Contact: Ron Burkey <info@sandroid.org>.
053449,000008: # Website: www.ibiblio.org/apollo.
053450,000009: # Pages: 1236-1242
053451,000010: # Mod history: 2009-05-14 RSB Adapted from the Colossus249/ file of the
053452,000011: # same name, using Comanche055 page images.
053453,000012:
053454,000013: # This source code has been transcribed or otherwise adapted from digitized
053455,000014: # images of a hardcopy from the MIT Museum. The digitization was performed
053456,000015: # by Paul Fjeld, and arranged for by Deborah Douglas of the Museum. Many
053457,000016: # thanks to both. The images (with suitable reduction in storage size and
053458,000017: # consequent reduction in image quality as well) are available online at
053459,000018: # www.ibiblio.org/apollo. If for some reason you find that the images are
053460,000019: # illegible, contact me at info@sandroid.org about getting access to the
053461,000020: # (much) higher-quality images which Paul actually created.
053462,000021:
053463,000022: # Notations on the hardcopy document read, in part:
053464,000023:
053465,000024: # Assemble revision 055 of AGC program Comanche by NASA
053466,000025: # 2021113-051. 10:28 APR. 1, 1969
053467,000026:
053468,000027: # This AGC program shall also be referred to as
053469,000028: # Colossus 2A
053470,000029:
053471,000030: # Page 1236
053472,000031: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
053473,000032:
053474,000033: # CALLING SEQUENCE
053475,000034: # L-1 CALL
053476,000035: # L LAT-LONG
053477,000036:
053478,000037: # SUBROUTINES USED
053479,000038: # R-TO-RP, ARCTAN, SETGAMMA, SETRE
053480,000039:
053481,000040: # ERASABLE INIT. REQ.
053482,000041: # AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
053483,000042: # ALPHAV = POSITION VECTOR METERS B-29
053484,000043: # MPAC -- TIME (CSECS B-28)
053485,000044: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
053486,000045: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
053487,000046:
053488,000047: # OUTPUT
053489,000048: # LATITUDE IN LAT (REVS. B-0)
053490,000049: # LONGITUDE IN LONG (REVS. B-0)
053491,000050: # ALTITUDE IN ALT METERS B-29
053492,000051:
053493,000052: 30,3750 BANK 30
053494,000053: 13,2000 SETLOC LATLONG
053495,000054: 13,2000 BANK
053496,000055:
053497,000056: 13,2370 COUNT 13/LT-LG
053498,000057:
053499,000058: 13,2370 E4,1551 EBANK= ALPHAV
053500,000059: 13,2370 40220 LAT-LONG STQ SETPD
053501,000060: 13,2371 02242 INCORPEX
053502,000061: 13,2372 00001 0D
053503,000062: 13,2373 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
053504,000063: 13,2374 02152 ALPHAV
053505,000064: 13,2375 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
053506,000065: 13,2376 16310 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
053507,000066: 13,2377 11566 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
053508,000067: 13,2400 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
053509,000068: 13,2401 01743 LUNAFLAG # 0=EARTH, 1=MOON
053510,000069: 13,2402 26403 CALLRTRP
053511,000070: 13,2403 77624 CALLRTRP CALL
053512,000071: 13,2404 55371 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
053513,000072: 13,2405 77656 UNIT # UNIT RP B-1
053514,000073: 13,2406 36152 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
053515,000074: 13,2407 26571 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
053516,000075: 13,2410 77624 CALL # SCALED B-1.
053517,000076: 13,2411 26601 SETRE # CALC RE METERS B-29
053518,000077: 13,2412 63545 DLOAD DSQ
053519,000078: 13,2413 02152 ALPHAV
053520,000079: 13,2414 63525 PDDL DSQ
053521,000080: 13,2415 02154 ALPHAV +2
053522,000081: # Page 1237
053523,000082: 13,2416 75415 DAD SQRT
053524,000083: 13,2417 76405 DMP SL1R
053525,000084: 13,2420 00011 GAMRP
053526,000085: 13,2421 14021 STODL COSTH # COS(LAT) B-1
053527,000086: 13,2422 02156 ALPHAV +4
053528,000087: 13,2423 34023 STCALL SINTH # SIN(LAT) B-1
053529,000088: 13,2424 26531 ARCTAN
053530,000089: 13,2425 15104 STODL LAT # LAT B0
053531,000090: 13,2426 02152 ALPHAV
053532,000091: 13,2427 14021 STODL COSTH # COS(LONG) B-1
053533,000092: 13,2430 02154 ALPHAV +2
053534,000093: 13,2431 34023 STCALL SINTH # SIN(LONG) B-1
053535,000094: 13,2432 26531 ARCTAN
053536,000095: 13,2433 15106 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
053537,000096: 13,2434 02310 ALPHAM
053538,000097: 13,2435 77625 DSU # ALT= R-RE METERS B-29
053539,000098: 13,2436 02241 ERADM
053540,000099: 13,2437 35110 STCALL ALT # EXIT WITH ALT METERS B-29
053541,000100: 13,2440 02242 INCORPEX
053542,000101: # Page 1238
053543,000102: # SUBROUTINE TO CONVERT LAT,LONG.ALT AT GIVEN TIME TO RADIUS VECTOR
053544,000103:
053545,000104: # CALLING SEQUENCE
053546,000105: # L-1 CALL
053547,000106: # L LALOTORV
053548,000107:
053549,000108: # SUBROUTINES USED
053550,000109: # SETGAMMA, SETRE, RP-TO-R
053551,000110:
053552,000111: # ERASABLE INIT. REQ.
053553,000112: # AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
053554,000113: # LAT -- LATITUDE (REVS B0)
053555,000114: # LONG -- LONGITUDE (REVS B0)
053556,000115: # ALT -- ALTITUDE (METERS) B-29
053557,000116: # MPAC -- TIME (CSECS B-28)
053558,000117: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
053559,000118: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
053560,000119:
053561,000120: # OUTPUT
053562,000121: # R-VECTOR IN ALPHAV (METERS B-29)
053563,000122:
053564,000123: 13,2441 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
053565,000124: 13,2442 02242 INCORPEX
053566,000125: 13,2443 00001 0D
053567,000126: 13,2444 34007 STCALL 6D # 6-7D = TIME FOR RP-TO-R
053568,000127: 13,2445 26571 SETGAMMA # GAMMA = B2/A2 FOR EARTH, 1 FOR MOON B-1
053569,000128: 13,2446 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
053570,000129: 13,2447 01104 LAT # UNIT RP = SIN(LONG)COS(LAT) 2-3D
053571,000130: 13,2450 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
053572,000131: 13,2451 00011 GAMRP
053573,000132: 13,2452 01104 LAT # 0-1D = GAMMA*SIN(LAT) B-2
053574,000133: 13,2453 65346 COS PDDL # PD4 2-3D= COS(LAT) B-1 TEMPORARILY
053575,000134: 13,2454 01106 LONG
053576,000135: 13,2455 57356 SIN DMPR # PD 2
053577,000136: 13,2456 71525 PDDL COS # PD 4 2-3D= SIN(LONG)COS(LAT) B-2
053578,000137: 13,2457 01104 LAT
053579,000138: 13,2460 71525 PDDL COS # PD 6 4-5D= COS(LAT) B-1 TEMPORARILY
053580,000139: 13,2461 01106 LONG
053581,000140: 13,2462 55475 DMPR VDEF # PD4 MPAC = COS(LONG)COS(LAT) B-2
053582,000141: 13,2463 41456 UNIT PUSH # 0-5D = UNIT RP FOR RP-TO-R SUBR.
053583,000142: 13,2464 36152 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
053584,000143: 13,2465 26601 SETRE # RE METERS B-29
053585,000144: 13,2466 43145 DLOAD BOFF # SET MPAC = 0 FOR EARTH, NON-ZERO FOR MOON
053586,000145: 13,2467 11566 ZEROVEC
053587,000146: 13,2470 01743 LUNAFLAG
053588,000147: 13,2471 26473 CALLRPRT
053589,000148: 13,2472 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
053590,000149: 13,2473 77624 CALLRPRT CALL
053591,000150: 13,2474 55344 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
053592,000151: 13,2475 16152 STODL ALPHAV
053593,000152: 13,2476 02241 ERADM
053594,000153: # Page 1239
053595,000154: 13,2477 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
053596,000155: 13,2500 01110 ALT
053597,000156: 13,2501 02152 ALPHAV
053598,000157: 13,2502 77772 VSL1 # R METERS B-29
053599,000158: 13,2503 36152 STCALL ALPHAV # EXIT WITH R IN METERS B-29
053600,000159: 13,2504 02242 INCORPEX
053601,000160:
053602,000161: # SUBROUTINE TO COMPUTE EARTH RADIUS
053603,000162:
053604,000163: # INPUT
053605,000164: # 1/2 SIN LAT IN ALPHAV +4
053606,000165:
053607,000166: # OUTPUT
053608,000167: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
053609,000168:
053610,000169: 13,2505 63545 GETERAD DLOAD DSQ
053611,000170: 13,2506 02156 ALPHAV +4 # SIN**2(L)
053612,000171: 13,2507 44352 SL1 BDSU
053613,000172: 13,2510 11564 DP1/2 # COS**2(L)
053614,000173: 13,2511 44275 DMPR BDSU
053615,000174: 13,2512 26526 EE
053616,000175: 13,2513 11564 DP1/2
053617,000176: 13,2514 75465 BDDV SQRT
053618,000177: 13,2515 26522 B2XSC
053619,000178: 13,2516 77622 SR4R
053620,000179: 13,2517 02241 STORE ERADM
053621,000180: 13,2520 77616 RVQ
053622,000181:
053623,000182: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
053624,000183: # B2XSC = B**2 SCALED B-51
053625,000184: # B2/A2 = B**2/A**2 SCALED B-1
053626,000185: # EE = (1-B**2/A**2) SCALED B-0
053627,000186:
053628,000187: 13,2521 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
053629,000188:
053630,000189: 13,2523 04,3563 DP1/2 = XUNIT
053631,000190: 13,2523 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
053632,000191:
053633,000192: 13,2525 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
053634,000193:
053635,000194: 13,2527 00302 17755 ERAD 2DEC 6373338 B-29 # PAD RADIUS
053636,000195:
053637,000196: # Page 1240
053638,000197: # ARCTAN SUBROUTINE
053639,000198:
053640,000199: # CALLING SEQUENCE
053641,000200: # SIN THETA IN SINTH B-1
053642,000201: # COS THETA IN COSTH B-1
053643,000202: # CALL ARCTAN
053644,000203:
053645,000204: # OUTPUT
053646,000205: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
053647,000206:
053648,000207: 13,2531 77600 ARCTAN BOV
053649,000208: 13,2532 26533 CLROVFLW
053650,000209: 13,2533 63545 CLROVFLW DLOAD DSQ
053651,000210: 13,2534 00023 SINTH
053652,000211: 13,2535 63525 PDDL DSQ
053653,000212: 13,2536 00021 COSTH
053654,000213: 13,2537 77615 DAD
053655,000214: 13,2540 75454 BZE SQRT
053656,000215: 13,2541 26557 ARCTANXX # ATAN=0/0. SET THETA=0
053657,000216: 13,2542 40065 BDDV BOV
053658,000217: 13,2543 00023 SINTH
053659,000218: 13,2544 26564 ATAN=90
053660,000219: 13,2545 67542 SR1 ASIN
053661,000220: 13,2546 00025 STORE THETA
053662,000221: 13,2547 50125 PDDL BMN
053663,000222: 13,2550 00021 COSTH
053664,000223: 13,2551 26553 NEGCOS
053665,000224: 13,2552 43545 DLOAD RVQ
053666,000225: 13,2553 57545 NEGCOS DLOAD DCOMP
053667,000226: 13,2554 43244 BPL DAD
053668,000227: 13,2555 26561 NEGOUT
053669,000228: 13,2556 11564 DP1/2
053670,000229: 13,2557 00025 ARCTANXX STORE THETA
053671,000230: 13,2560 77616 RVQ
053672,000231:
053673,000232: 13,2561 52025 NEGOUT DSU GOTO
053674,000233: 13,2562 11564 DP1/2
053675,000234: 13,2563 26557 ARCTANXX
053676,000235: 13,2564 75345 ATAN=90 DLOAD SIGN
053677,000236: 13,2565 11612 LODP1/4
053678,000237: 13,2566 00023 SINTH
053679,000238: 13,2567 00025 STORE THETA
053680,000239: 13,2570 77616 RVQ
053681,000240:
053682,000241: 13,2571 04,3565 2DZERO = DPZERO
053683,000242:
053684,000243: # Page 1241
053685,000244: # ***** SETGAMMA SUBROUTINE *****
053686,000245: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
053687,000246:
053688,000247: # GAMMA = B**2/A**2 FOR EARTH (B-1)
053689,000248: # GAMMA = 1 FOR MOON (B-1)
053690,000249:
053691,000250: # CALLING SEQUENCE
053692,000251: # L CALL
053693,000252: # L+1 SETGAMMA
053694,000253:
053695,000254: # INPUT
053696,000255: # LUNAFLAG=0 FOR EARTH, =1 FOR MOON
053697,000256:
053698,000257: # OUTPUT
053699,000258: # GAMMA IN GAMRP (B-1)
053700,000259:
053701,000260: 13,2571 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
053702,000261: 13,2572 26524 B2/A2 # EARTH GAMMA
053703,000262: 13,2573 01743 LUNAFLAG
053704,000263: 13,2574 26577 SETGMEX
053705,000264: 13,2575 77735 SLOAD
053706,000265: 13,2576 11564 1B1 # MOON GAMMA
053707,000266: 13,2577 00011 SETGMEX STORE GAMRP
053708,000267: 13,2600 77616 RVQ
053709,000268: 13,2601 GAMRP = 8D
053710,000269:
053711,000270: # Page 1242
053712,000271: # ***** SETRE SUBROUTINE *****
053713,000272: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
053714,000273:
053715,000274: # RE = RM FOR MOON
053716,000275: # RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
053717,000276:
053718,000277: # CALLING SEQUENCE
053719,000278: # L CALL
053720,000279: # L+1 SETRE
053721,000280:
053722,000281: # SUBROUTINES USED
053723,000282: # CETERAD
053724,000283:
053725,000284: # INPUT
053726,000285: # ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
053727,000286: # ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
053728,000287: # LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
053729,000288:
053730,000289: # OUTPUT
053731,000290: # ERADM = 504RM FOR MOON (METERS B-29)
053732,000291: # ERADM = ERAD OR COMPUTED RE FOR EARTH (METERS B-29)
053733,000292:
053734,000293: 13,2601 71220 SETRE STQ DLOAD
053735,000294: 13,2602 00051 SETREX
053736,000295: 13,2603 26626 504RM
053737,000296: 13,2604 71214 BON DLOAD # BRANCH FOR MOON
053738,000297: 13,2605 01703 LUNAFLAG
053739,000298: 13,2606 26616 TSTRLSRM
053740,000299: 13,2607 26530 ERAD
053741,000300: 13,2610 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
053742,000301: 13,2611 00742 ERADFLAG
053743,000302: 13,2612 26614 SETRXX
053744,000303: 13,2613 26505 GETERAD
053745,000304: 13,2614 36241 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
053746,000305: 13,2615 00051 SETREX
053747,000306: 13,2616 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
053748,000307: 13,2617 00702 ERADFLAG # =1 R0=RM
053749,000308: 13,2620 26614 SETRXX
053750,000309: 13,2621 02026 RLS
053751,000310: 13,2622 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
053752,000311: 13,2623 77650 GOTO
053753,000312: 13,2624 26614 SETRXX
053754,000313: 13,2625 0000051 SETREX = S2
053755,000314: 13,2625 00065 01265 504RM 2DEC 1738090 B-29 # METERS B-29 (MOON RADIUS)
053756,000315:
053757,000316:
053758,000317:
053759,000318:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc