Source Code
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These source-code files are part of a reconstructed copy of Luminary 173, the
second (unflown) release of the Apollo 14 Lunar Module (LM) Apollo Guidance
Computer (AGC) software.
The reconstruction began with reconstructed source code for Luminary 178. Changes
between revision 173 and 178 were backed out, as described by Luminary memo 167
(revision 1). The reconstruction was verified by matching memory-bank checksums
to those listed in drawing 2021152N. Note that page numbers in the reconstructed
code match those for the baseline log section mentioned in each file's changelog;
the page numbers for a real Luminary 173 listing would be different.
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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047644,000002: ## Copyright: Public domain.
047645,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
047646,000004: ## Purpose: A section of Luminary revision 173.
047647,000005: ## It is part of the reconstructed source code for the second
047648,000006: ## (unflown) release of the flight software for the Lunar
047649,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 14.
047650,000008: ## The code has been recreated from a reconstructed copy of
047651,000009: ## Luminary 178, as well as Luminary memo 167 (revision 1).
047652,000010: ## It has been adapted such that the resulting bugger words
047653,000011: ## exactly match those specified for Luminary 173 in NASA
047654,000012: ## drawing 2021152N, which gives relatively high confidence
047655,000013: ## that the reconstruction is correct.
047656,000014: ## Reference: pp. 1124-1130
047657,000015: ## Assembler: yaYUL
047658,000016: ## Contact: Ron Burkey <info@sandroid.org>.
047659,000017: ## Website: www.ibiblio.org/apollo/index.html
047660,000018: ## Mod history: 2019-09-18 MAS Created from Luminary 178.
047661,000019:
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Page 1124
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047663,000021: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047664,000022:
047665,000023: # CALLING SEQUENCE
047666,000024:
047667,000025: # L-1 CALL
047668,000026: # L LAT-LONG
047669,000027: # SUBROUTINES USED
047670,000028:
047671,000029: # R-TO-RP,ARCTAN,SETGAMMA,SETRE
047672,000030: # ERASABLE INIT. REQ.
047673,000031:
047674,000032: # AXO,-AYO,AZO,TEPHEM (SET AT LAUNCH TIME)
047675,000033: # ALPHAV = POSITION VECTOR METERS B-29
047676,000034: # MPAC-- TIME (CSECS B-28)
047677,000035: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047678,000036: # LUNAFLAG=0 FOR EARTH,1 FOR MOON
047679,000037: # OUTPUT
047680,000038:
047681,000039: # LATITUDE IN LAT (REVS. B-0)
047682,000040: # LONGITUDE IN LONG (REVS. B-0)
047683,000041: # ALTITUDE IN ALT METERS B-29
047684,000042: 30,3760 BANK 30
047685,000043: 13,2000 SETLOC LATLONG
047686,000044: 13,2000 BANK
047687,000045:
047688,000046: 13,2347 COUNT* $$/LT-LG
047689,000047: 13,2347 E4,1431 EBANK= ALPHAV
047690,000048: 13,2347 40220 LAT-LONG STQ SETPD
047691,000049: 13,2350 03674 INCORPEX
047692,000050: 13,2351 00001 0D
047693,000051: 13,2352 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
047694,000052: 13,2353 02032 ALPHAV
047695,000053: 13,2354 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
047696,000054: 13,2355 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
047697,000055: 13,2356 24007 ZEROVEC # SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047698,000056: 13,2357 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
047699,000057: 13,2360 01743 LUNAFLAG # 0=EARTH,1=MOON
047700,000058: 13,2361 26362 CALLRTRP
047701,000059: 13,2362 77624 CALLRTRP CALL
047702,000060: 13,2363 51642 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
047703,000061: 13,2364 77656 UNIT # UNIT RP B-1
047704,000062: 13,2365 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
047705,000063: 13,2366 26546 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH,=1 FOR MOON
047706,000064: 13,2367 77624 CALL # SCALED B-1
047707,000065: 13,2370 26556 SETRE # CALC RE METERS B-29
047708,000066: 13,2371 63545 DLOAD DSQ
047709,000067: 13,2372 02032 ALPHAV
047710,000068: 13,2373 63525 PDDL DSQ
047711,000069: 13,2374 02034 ALPHAV +2
047712,000070: 13,2375 75415 DAD SQRT
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Page 1125
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047714,000072: 13,2376 76405 DMP SL1R
047715,000073: 13,2377 00011 GAMRP
047716,000074: 13,2400 14021 STODL COSTH # COS(LAT) B-1
047717,000075: 13,2401 02036 ALPHAV +4
047718,000076: 13,2402 34023 STCALL SINTH # SIN(LAT) B-1
047719,000077: 13,2403 26506 ARCTAN
047720,000078: 13,2404 15120 STODL LAT # LAT B0
047721,000079: 13,2405 02032 ALPHAV
047722,000080: 13,2406 14021 STODL COSTH # COS(LONG) B-1
047723,000081: 13,2407 02034 ALPHAV +2
047724,000082: 13,2410 34023 STCALL SINTH # SIN(LONG) B-1
047725,000083: 13,2411 26506 ARCTAN
047726,000084: 13,2412 15122 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047727,000085: 13,2413 02070 ALPHAM
047728,000086: 13,2414 77625 DSU # ALT= R-RE METERS B-29
047729,000087: 13,2415 03673 ERADM
047730,000088: 13,2416 35124 STCALL ALT # EXIT WITH ALT METERS B-29
047731,000089: 13,2417 03674 INCORPEX
047732,000090:
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Page 1126
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047734,000092: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047735,000093: # CALLING SEQUENCE
047736,000094:
047737,000095: # L-1 CALL
047738,000096: # L LALOTORV
047739,000097: # SUBROUTINES USED
047740,000098:
047741,000099: # SETGAMMA,SETRE,RP-TO-R
047742,000100: # ERASABLE INIT. REQ.
047743,000101:
047744,000102: # AXO,AYO,AZO,TEPHEM SET AT LAUNCH TIME
047745,000103: # LAT-- LATITUDE (REVS B0)
047746,000104: # LONG-- LONGITUDE (REVS B0)
047747,000105: # ALT--ALTITUDE (METERS) B-29
047748,000106: # MPAC-- TIME (CSECS B-28)
047749,000107: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047750,000108: # LUNAFLAG=0 FOR EARTH,1 FOR MOON
047751,000109: # OUTPUT
047752,000110:
047753,000111: # R-VECTOR IN ALPHAV (METERS B-29)
047754,000112: 13,2420 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
047755,000113: 13,2421 03674 INCORPEX
047756,000114: 13,2422 00001 0D
047757,000115: 13,2423 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
047758,000116: 13,2424 26546 SETGAMMA # GAMMA=B2/A2 FOR EARTH,1 FOR MOON B-1
047759,000117: 13,2425 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
047760,000118: 13,2426 01120 LAT # UNIT RP= SIN(LONG)COS(LAT) 2-3D
047761,000119: 13,2427 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
047762,000120: 13,2430 00011 GAMRP
047763,000121: 13,2431 01120 LAT # 0-1D= GAMMA*SIN(LAT) B-2
047764,000122: 13,2432 65346 COS PDDL # PD4 2-3D=COS(LAT) B-1 TEMPORARILY
047765,000123: 13,2433 01122 LONG
047766,000124: 13,2434 57356 SIN DMPR # PD 2
047767,000125: 13,2435 71525 PDDL COS # PD 4 2-3D=SIN(LONG)COS(LAT) B-2
047768,000126: 13,2436 01120 LAT
047769,000127: 13,2437 71525 PDDL COS # PD 6 4-5D=COS(LAT) B-1 TEMPORARILY
047770,000128: 13,2440 01122 LONG
047771,000129: 13,2441 55475 DMPR VDEF # PD 4 MPAC= COS(LONG)COS(LAT) B-2
047772,000130: 13,2442 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
047773,000131: 13,2443 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
047774,000132: 13,2444 26556 SETRE # RE METERS B-29
047775,000133: 13,2445 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047776,000134: 13,2446 24007 ZEROVEC
047777,000135: 13,2447 01743 LUNAFLAG
047778,000136: 13,2450 26452 CALLRPRT
047779,000137: 13,2451 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
047780,000138: 13,2452 77624 CALLRPRT CALL
047781,000139: 13,2453 55720 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
047782,000140: 13,2454 16032 STODL ALPHAV
047783,000141: 13,2455 03673 ERADM
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Page 1127
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047785,000143: 13,2456 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
047786,000144: 13,2457 01124 ALT
047787,000145: 13,2460 02032 ALPHAV
047788,000146: 13,2461 77772 VSL1 # R METERS B-29
047789,000147: 13,2462 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
047790,000148: 13,2463 03674 INCORPEX
047791,000149: # SUBROUTINE TO COMPUTE EARTH RADIUS
047792,000150:
047793,000151: # INPUT
047794,000152:
047795,000153: # 1/2 SIN LAT IN ALPHAV +4
047796,000154:
047797,000155: # OUTPUT
047798,000156:
047799,000157: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047800,000158:
047801,000159: 13,2464 63545 GETERAD DLOAD DSQ
047802,000160: 13,2465 02036 ALPHAV +4 # SIN**2(L)
047803,000161: 13,2466 44352 SL1 BDSU
047804,000162: 13,2467 24005 DP1/2 # COS**2(L)
047805,000163: 13,2470 44275 DMPR BDSU
047806,000164: 13,2471 26505 EE
047807,000165: 13,2472 24005 DP1/2
047808,000166: 13,2473 75465 BDDV SQRT
047809,000167: 13,2474 26501 B2XSC
047810,000168: 13,2475 77622 SR4R
047811,000169: 13,2476 03673 STORE ERADM
047812,000170: 13,2477 77616 RVQ
047813,000171:
047814,000172: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166,B=6356784 METERS
047815,000173: # B2XSC= B**2 SCALED B-51
047816,000174: # B2/A2= B**2/A**2 SCALED B-1
047817,000175: # EE=(1-B**2/A**2) SCALED B-0
047818,000176: 13,2500 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
047819,000177:
047820,000178: 13,2502 12,2004 DP1/2 = XUNIT
047821,000179: 13,2502 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
047822,000180:
047823,000181: 13,2504 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
047824,000182:
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Page 1128
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047826,000184: # ARCTAN SUBROUTINE
047827,000185:
047828,000186:
047829,000187: # CALLING SEQUENCE
047830,000188:
047831,000189: # SIN THETA IN SINTH B-1
047832,000190: # COS THETA IN COSTH B-1
047833,000191: # CALL ARCTAN
047834,000192:
047835,000193: # OUTPUT
047836,000194: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047837,000195:
047838,000196:
047839,000197: 13,2506 77600 ARCTAN BOV
047840,000198: 13,2507 26510 CLROVFLW
047841,000199: 13,2510 63545 CLROVFLW DLOAD DSQ
047842,000200: 13,2511 00023 SINTH
047843,000201: 13,2512 63525 PDDL DSQ
047844,000202: 13,2513 00021 COSTH
047845,000203: 13,2514 77615 DAD
047846,000204: 13,2515 75454 BZE SQRT
047847,000205: 13,2516 26534 ARCTANXX # ATAN=0/0 SET THETA=0
047848,000206: 13,2517 40065 BDDV BOV
047849,000207: 13,2520 00023 SINTH
047850,000208: 13,2521 26541 ATAN=90
047851,000209: 13,2522 67542 SR1 ASIN
047852,000210: 13,2523 00025 STORE THETA
047853,000211: 13,2524 50125 PDDL BMN
047854,000212: 13,2525 00021 COSTH
047855,000213: 13,2526 26530 NEGCOS
047856,000214: 13,2527 43545 DLOAD RVQ
047857,000215: 13,2530 57545 NEGCOS DLOAD DCOMP
047858,000216: 13,2531 43244 BPL DAD
047859,000217: 13,2532 26536 NEGOUT
047860,000218: 13,2533 24005 DP1/2
047861,000219: 13,2534 00025 ARCTANXX STORE THETA
047862,000220: 13,2535 77616 RVQ
047863,000221:
047864,000222: 13,2536 52025 NEGOUT DSU GOTO
047865,000223: 13,2537 24005 DP1/2
047866,000224: 13,2540 26534 ARCTANXX
047867,000225: 13,2541 75345 ATAN=90 DLOAD SIGN
047868,000226: 13,2542 11011 LODP1/4
047869,000227: 13,2543 00023 SINTH
047870,000228: 13,2544 00025 STORE THETA
047871,000229: 13,2545 77616 RVQ
047872,000230:
047873,000231: 13,2546 12,2006 2DZERO = DPZERO
047874,000232:
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Page 1129
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047876,000234: # ..... SETGAMMA SUBROUTINE .....
047877,000235: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047878,000236:
047879,000237: # GAMMA = B**2/A**2 FOR EARTH (B-1)
047880,000238: # GAMMA = 1 FOR MOON (B-1)
047881,000239:
047882,000240: # CALLING SEQUENCE
047883,000241: # L CALL
047884,000242: # L+1 SETGAMMA
047885,000243:
047886,000244: # INPUT
047887,000245: # LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047888,000246:
047889,000247: # OUTPUT
047890,000248: # GAMMA IN GAMRP (B-1)
047891,000249:
047892,000250: 13,2546 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
047893,000251: 13,2547 26503 B2/A2 # EARTH GAMMA
047894,000252: 13,2550 01743 LUNAFLAG
047895,000253: 13,2551 26554 SETGMEX
047896,000254: 13,2552 77735 SLOAD
047897,000255: 13,2553 24005 1B1 # MOON GAMMA
047898,000256: 13,2554 00011 SETGMEX STORE GAMRP
047899,000257: 13,2555 77616 RVQ
047900,000258: 13,2556 GAMRP = 8D
047901,000259:
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Page 1130
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047903,000261: # .....SETRE SUBROUTINE .....
047904,000262: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047905,000263:
047906,000264: # RE= RM FOR MOON
047907,000265: # RE= RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047908,000266:
047909,000267: # CALLING SEQUENCE
047910,000268: # L CALL
047911,000269: # L+1 SETRE
047912,000270:
047913,000271: # SUBROUTINES USED
047914,000272: # GETERAD
047915,000273:
047916,000274: # INPUT
047917,000275: # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED RE
047918,000276: # ALPHAV +4= 1/2 SINL IF GETERAD IS CALLED
047919,000277: # LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047920,000278:
047921,000279: # OUTPUT
047922,000280: # ERADM= 504RM FOR MOON (METERS B-29)
047923,000281: # ERADM= ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047924,000282:
047925,000283: 13,2556 71220 SETRE STQ DLOAD
047926,000284: 13,2557 00051 SETREX
047927,000285: 13,2560 10003 504RM
047928,000286: 13,2561 71214 BON DLOAD # BRANCH FOR MOON
047929,000287: 13,2562 01703 LUNAFLAG
047930,000288: 13,2563 26573 TSTRLSRM
047931,000289: 13,2564 10001 ERAD
047932,000290: 13,2565 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE,1 FOR COMPUTED
047933,000291: 13,2566 00742 ERADFLAG
047934,000292: 13,2567 26571 SETRXX
047935,000293: 13,2570 26464 GETERAD
047936,000294: 13,2571 37673 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
047937,000295: 13,2572 00051 SETREX
047938,000296: 13,2573 77214 TSTRLSRM BON VLOAD # ERADFLAG=0,SET R0=RLS
047939,000297: 13,2574 00702 ERADFLAG # =1 R0=RM
047940,000298: 13,2575 26571 SETRXX
047941,000299: 13,2576 02021 RLS
047942,000300: 13,2577 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
047943,000301: 13,2600 77650 GOTO
047944,000302: 13,2601 26571 SETRXX
047945,000303: 13,2602 0000051 SETREX = S2
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc