Source Code
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These source-code files are part of a reconstructed copy of Comanche 72, the
first release of the Apollo Guidance Computer (AGC) Command Module (CM) software
for Apollo 13.
They have been adapted from sources files created from a listing of Comanche 55.
These source files were updated to match binary dumps of a set of Comanche 67 rope modules.
They were then further modified by applying known changes between Comanche 67 and Comanche 72.
A binary dump of module B2 of Comanche 72, part number 2010802-021, was also used
to validate changes made to banks 05-13. The resulting code assembles to have identical
memory-bank checksums as those specified in NASA drawing 2021153G; this gives reasonably
high confidence that the changes that have been made are correct. In places where
ambiguity exists, this ambiguity is discussed in "## Reconstruction:" comments.
Since no contemporary listings of Comanche 72 are available as source material,
all comments and labels are approximate.
They have been taken from other AGC programs where possible, or, in some places, written
from scratch to match what we believe would have been in the original listing.
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051622,000002: ## Copyright: Public domain.
051623,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
051624,000004: ## Purpose: A section of Comanche revision 072.
051625,000005: ## It is part of the reconstructed source code for the first
051626,000006: ## release of the software for the Command Module's (CM) Apollo
051627,000007: ## Guidance Computer (AGC) for Apollo 13. No original listings
051628,000008: ## of this program are available; instead, this file was recreated
051629,000009: ## from a printout of Comanche 055, binary dumps of a set of
051630,000010: ## Comanche 067 rope modules, and changelogs between Comanche 067
051631,000011: ## and 072. It has been adapted such that the resulting bugger words
051632,000012: ## exactly match those specified for Comanche 072 in NASA drawing
051633,000013: ## 2021153G, which gives relatively high confidence that the
051634,000014: ## reconstruction is correct.
051635,000015: ## Assembler: yaYUL
051636,000016: ## Contact: Ron Burkey <info@sandroid.org>.
051637,000017: ## Website: www.ibiblio.org/apollo/index.html
051638,000018: ## Mod history: 2024-05-13 MAS Created from Comanche 067.
051639,000019:
051640,000020: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
051641,000021:
051642,000022: # CALLING SEQUENCE
051643,000023: # L-1 CALL
051644,000024: # L LAT-LONG
051645,000025:
051646,000026: # SUBROUTINES USED
051647,000027: # R-TO-RP, ARCTAN, SETGAMMA, SETRE
051648,000028:
051649,000029: # ERASABLE INIT. REQ.
051650,000030: # AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
051651,000031: # ALPHAV = POSITION VECTOR METERS B-29
051652,000032: # MPAC -- TIME (CSECS B-28)
051653,000033: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
051654,000034: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
051655,000035:
051656,000036: # OUTPUT
051657,000037: # LATITUDE IN LAT (REVS. B-0)
051658,000038: # LONGITUDE IN LONG (REVS. B-0)
051659,000039: # ALTITUDE IN ALT METERS B-29
051660,000040:
051661,000041: 30,3750 BANK 30
051662,000042: 13,2000 SETLOC LATLONG
051663,000043: 13,2000 BANK
051664,000044:
051665,000045: 13,2376 COUNT 13/LT-LG
051666,000046:
051667,000047: 13,2376 E4,1551 EBANK= ALPHAV
051668,000048: 13,2376 40220 LAT-LONG STQ SETPD
051669,000049: 13,2377 02242 INCORPEX
051670,000050: 13,2400 00001 0D
051671,000051: 13,2401 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
051672,000052: 13,2402 02152 ALPHAV
051673,000053: 13,2403 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
051674,000054: 13,2404 16310 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
051675,000055: 13,2405 11566 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
051676,000056: 13,2406 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
051677,000057: 13,2407 01743 LUNAFLAG # 0=EARTH, 1=MOON
051678,000058: 13,2410 26411 CALLRTRP
051679,000059: 13,2411 77624 CALLRTRP CALL
051680,000060: 13,2412 55370 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
051681,000061: 13,2413 77656 UNIT # UNIT RP B-1
051682,000062: 13,2414 36152 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
051683,000063: 13,2415 26577 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
051684,000064: 13,2416 77624 CALL # SCALED B-1
051685,000065: 13,2417 26607 SETRE # CALC RE METERS B-29
051686,000066: 13,2420 63545 DLOAD DSQ
051687,000067: 13,2421 02152 ALPHAV
051688,000068: 13,2422 63525 PDDL DSQ
051689,000069: 13,2423 02154 ALPHAV +2
051690,000070: 13,2424 75415 DAD SQRT
051691,000071: 13,2425 76405 DMP SL1R
051692,000072: 13,2426 00011 GAMRP
051693,000073: 13,2427 14021 STODL COSTH # COS(LAT) B-1
051694,000074: 13,2430 02156 ALPHAV +4
051695,000075: 13,2431 34023 STCALL SINTH # SIN(LAT) B-1
051696,000076: 13,2432 26537 ARCTAN
051697,000077: 13,2433 15104 STODL LAT # LAT B0
051698,000078: 13,2434 02152 ALPHAV
051699,000079: 13,2435 14021 STODL COSTH # COS(LONG) B-1
051700,000080: 13,2436 02154 ALPHAV +2
051701,000081: 13,2437 34023 STCALL SINTH # SIN(LONG) B-1
051702,000082: 13,2440 26537 ARCTAN
051703,000083: 13,2441 15106 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
051704,000084: 13,2442 02310 ALPHAM
051705,000085: 13,2443 77625 DSU # ALT= R-RE METERS B-29
051706,000086: 13,2444 02241 ERADM
051707,000087: 13,2445 35110 STCALL ALT # EXIT WITH ALT METERS B-29
051708,000088: 13,2446 02242 INCORPEX
051709,000089: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
051710,000090:
051711,000091: # CALLING SEQUENCE
051712,000092: # L-1 CALL
051713,000093: # L LALOTORV
051714,000094:
051715,000095: # SUBROUTINES USED
051716,000096: # SETGAMMA, SETRE, RP-TO-R
051717,000097:
051718,000098: # ERASABLE INIT. REQ.
051719,000099: # AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
051720,000100: # LAT -- LATITUDE (REVS B0)
051721,000101: # LONG -- LONGITUDE (REVS B0)
051722,000102: # ALT -- ALTITUDE (METERS) B-29
051723,000103: # MPAC -- TIME (CSECS B-28)
051724,000104: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
051725,000105: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
051726,000106:
051727,000107: # OUTPUT
051728,000108: # R-VECTOR IN ALPHAV (METERS B-29)
051729,000109:
051730,000110: 13,2447 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
051731,000111: 13,2450 02242 INCORPEX
051732,000112: 13,2451 00001 0D
051733,000113: 13,2452 34007 STCALL 6D # 6-7D = TIME FOR RP-TO-R
051734,000114: 13,2453 26577 SETGAMMA # GAMMA = B2/A2 FOR EARTH, 1 FOR MOON B-1
051735,000115: 13,2454 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
051736,000116: 13,2455 01104 LAT # UNIT RP = SIN(LONG)COS(LAT) 2-3D
051737,000117: 13,2456 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
051738,000118: 13,2457 00011 GAMRP
051739,000119: 13,2460 01104 LAT # 0-1D = GAMMA*SIN(LAT) B-2
051740,000120: 13,2461 65346 COS PDDL # PD4 2-3D= COS(LAT) B-1 TEMPORARILY
051741,000121: 13,2462 01106 LONG
051742,000122: 13,2463 57356 SIN DMPR # PD 2
051743,000123: 13,2464 71525 PDDL COS # PD 4 2-3D= SIN(LONG)COS(LAT) B-2
051744,000124: 13,2465 01104 LAT
051745,000125: 13,2466 71525 PDDL COS # PD 6 4-5D= COS(LAT) B-1 TEMPORARILY
051746,000126: 13,2467 01106 LONG
051747,000127: 13,2470 55475 DMPR VDEF # PD4 MPAC = COS(LONG)COS(LAT) B-2
051748,000128: 13,2471 41456 UNIT PUSH # 0-5D = UNIT RP FOR RP-TO-R SUBR.
051749,000129: 13,2472 36152 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
051750,000130: 13,2473 26607 SETRE # RE METERS B-29
051751,000131: 13,2474 43145 DLOAD BOFF # SET MPAC = 0 FOR EARTH, NON-ZERO FOR MOON
051752,000132: 13,2475 11566 ZEROVEC
051753,000133: 13,2476 01743 LUNAFLAG
051754,000134: 13,2477 26501 CALLRPRT
051755,000135: 13,2500 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
051756,000136: 13,2501 77624 CALLRPRT CALL
051757,000137: 13,2502 55343 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
051758,000138: 13,2503 16152 STODL ALPHAV
051759,000139: 13,2504 02241 ERADM
051760,000140: 13,2505 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
051761,000141: 13,2506 01110 ALT
051762,000142: 13,2507 02152 ALPHAV
051763,000143: 13,2510 77772 VSL1 # R METERS B-29
051764,000144: 13,2511 36152 STCALL ALPHAV # EXIT WITH R IN METERS B-29
051765,000145: 13,2512 02242 INCORPEX
051766,000146:
051767,000147: # SUBROUTINE TO COMPUTE EARTH RADIUS
051768,000148:
051769,000149: # INPUT
051770,000150: # 1/2 SIN LAT IN ALPHAV +4
051771,000151:
051772,000152: # OUTPUT
051773,000153: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
051774,000154:
051775,000155: 13,2513 63545 GETERAD DLOAD DSQ
051776,000156: 13,2514 02156 ALPHAV +4 # SIN**2(L)
051777,000157: 13,2515 44352 SL1 BDSU
051778,000158: 13,2516 11564 DP1/2 # COS**2(L)
051779,000159: 13,2517 44275 DMPR BDSU
051780,000160: 13,2520 26534 EE
051781,000161: 13,2521 11564 DP1/2
051782,000162: 13,2522 75465 BDDV SQRT
051783,000163: 13,2523 26530 B2XSC
051784,000164: 13,2524 77622 SR4R
051785,000165: 13,2525 02241 STORE ERADM
051786,000166: 13,2526 77616 RVQ
051787,000167:
051788,000168: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
051789,000169: # B2XSC = B**2 SCALED B-51
051790,000170: # B2/A2 = B**2/A**2 SCALED B-1
051791,000171: # EE = (1-B**2/A**2) SCALED B-0
051792,000172:
051793,000173: 13,2527 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
051794,000174:
051795,000175: 13,2531 04,3563 DP1/2 = XUNIT
051796,000176: 13,2531 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
051797,000177:
051798,000178: 13,2533 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
051799,000179:
051800,000180: 13,2535 00302 17755 ERAD 2DEC 6373338 B-29 # PAD RADIUS
051801,000181:
051802,000182: # ARCTAN SUBROUTINE
051803,000183:
051804,000184: # CALLING SEQUENCE
051805,000185: # SIN THETA IN SINTH B-1
051806,000186: # COS THETA IN COSTH B-1
051807,000187: # CALL ARCTAN
051808,000188:
051809,000189: # OUTPUT
051810,000190: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
051811,000191:
051812,000192: 13,2537 77600 ARCTAN BOV
051813,000193: 13,2540 26541 CLROVFLW
051814,000194: 13,2541 63545 CLROVFLW DLOAD DSQ
051815,000195: 13,2542 00023 SINTH
051816,000196: 13,2543 63525 PDDL DSQ
051817,000197: 13,2544 00021 COSTH
051818,000198: 13,2545 77615 DAD
051819,000199: 13,2546 75454 BZE SQRT
051820,000200: 13,2547 26565 ARCTANXX # ATAN=0/0 SET THETA=0
051821,000201: 13,2550 40065 BDDV BOV
051822,000202: 13,2551 00023 SINTH
051823,000203: 13,2552 26572 ATAN=90
051824,000204: 13,2553 67542 SR1 ASIN
051825,000205: 13,2554 00025 STORE THETA
051826,000206: 13,2555 50125 PDDL BMN
051827,000207: 13,2556 00021 COSTH
051828,000208: 13,2557 26561 NEGCOS
051829,000209: 13,2560 43545 DLOAD RVQ
051830,000210: 13,2561 57545 NEGCOS DLOAD DCOMP
051831,000211: 13,2562 43244 BPL DAD
051832,000212: 13,2563 26567 NEGOUT
051833,000213: 13,2564 11564 DP1/2
051834,000214: 13,2565 00025 ARCTANXX STORE THETA
051835,000215: 13,2566 77616 RVQ
051836,000216:
051837,000217: 13,2567 52025 NEGOUT DSU GOTO
051838,000218: 13,2570 11564 DP1/2
051839,000219: 13,2571 26565 ARCTANXX
051840,000220: 13,2572 75345 ATAN=90 DLOAD SIGN
051841,000221: 13,2573 11612 LODP1/4
051842,000222: 13,2574 00023 SINTH
051843,000223: 13,2575 00025 STORE THETA
051844,000224: 13,2576 77616 RVQ
051845,000225:
051846,000226: 13,2577 04,3565 2DZERO = DPZERO
051847,000227:
051848,000228: # ..... SETGAMMA SUBROUTINE .....
051849,000229: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
051850,000230:
051851,000231: # GAMMA = B**2/A**2 FOR EARTH (B-1)
051852,000232: # GAMMA = 1 FOR MOON (B-1)
051853,000233:
051854,000234: # CALLING SEQUENCE
051855,000235: # L CALL
051856,000236: # L+1 SETGAMMA
051857,000237:
051858,000238: # INPUT
051859,000239: # LUNAFLAG=0 FOR EARTH, =1 FOR MOON
051860,000240:
051861,000241: # OUTPUT
051862,000242: # GAMMA IN GAMRP (B-1)
051863,000243:
051864,000244: 13,2577 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
051865,000245: 13,2600 26532 B2/A2 # EARTH GAMMA
051866,000246: 13,2601 01743 LUNAFLAG
051867,000247: 13,2602 26605 SETGMEX
051868,000248: 13,2603 77735 SLOAD
051869,000249: 13,2604 11564 1B1 # MOON GAMMA
051870,000250: 13,2605 00011 SETGMEX STORE GAMRP
051871,000251: 13,2606 77616 RVQ
051872,000252: 13,2607 GAMRP = 8D
051873,000253:
051874,000254: # ..... SETRE SUBROUTINE .....
051875,000255: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
051876,000256:
051877,000257: # RE = RM FOR MOON
051878,000258: # RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
051879,000259:
051880,000260: # CALLING SEQUENCE
051881,000261: # L CALL
051882,000262: # L+1 SETRE
051883,000263:
051884,000264: # SUBROUTINES USED
051885,000265: # GETERAD
051886,000266:
051887,000267: # INPUT
051888,000268: # ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
051889,000269: # ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
051890,000270: # LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
051891,000271:
051892,000272: # OUTPUT
051893,000273: # ERADM = 504RM FOR MOON (METERS B-29)
051894,000274: # ERADM = ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
051895,000275:
051896,000276: 13,2607 71220 SETRE STQ DLOAD
051897,000277: 13,2610 00051 SETREX
051898,000278: 13,2611 26634 504RM
051899,000279: 13,2612 71214 BON DLOAD # BRANCH FOR MOON
051900,000280: 13,2613 01703 LUNAFLAG
051901,000281: 13,2614 26624 TSTRLSRM
051902,000282: 13,2615 26536 ERAD
051903,000283: 13,2616 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
051904,000284: 13,2617 00742 ERADFLAG
051905,000285: 13,2620 26622 SETRXX
051906,000286: 13,2621 26513 GETERAD
051907,000287: 13,2622 36241 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
051908,000288: 13,2623 00051 SETREX
051909,000289: 13,2624 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
051910,000290: 13,2625 00702 ERADFLAG # =1 R0=RM
051911,000291: 13,2626 26622 SETRXX
051912,000292: 13,2627 02026 RLS
051913,000293: 13,2630 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
051914,000294: 13,2631 77650 GOTO
051915,000295: 13,2632 26622 SETRXX
051916,000296: 13,2633 0000051 SETREX = S2
051917,000297: 13,2633 00065 01265 504RM 2DEC 1738090 B-29 # METERS B-29 (MOON RADIUS)
051918,000298:
051919,000299:
051920,000300:
051921,000301:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc