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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047631,000002: ## Copyright: Public domain.
047632,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
047633,000004: ## Purpose: A section of Luminary revision 173.
047634,000005: ## It is part of the reconstructed source code for the second
047635,000006: ## (unflown) release of the flight software for the Lunar
047636,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 14.
047637,000008: ## The code has been recreated from a reconstructed copy of
047638,000009: ## Luminary 178, as well as Luminary memo 167 (revision 1).
047639,000010: ## It has been adapted such that the resulting bugger words
047640,000011: ## exactly match those specified for Luminary 173 in NASA
047641,000012: ## drawing 2021152N, which gives relatively high confidence
047642,000013: ## that the reconstruction is correct.
047643,000014: ## Reference: pp. 1124-1130
047644,000015: ## Assembler: yaYUL
047645,000016: ## Contact: Ron Burkey <info@sandroid.org>.
047646,000017: ## Website: www.ibiblio.org/apollo/index.html
047647,000018: ## Mod history: 2019-09-18 MAS Created from Luminary 178.
047648,000019:
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Page 1124
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047650,000021: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047651,000022:
047652,000023: # CALLING SEQUENCE
047653,000024:
047654,000025: # L-1 CALL
047655,000026: # L LAT-LONG
047656,000027: # SUBROUTINES USED
047657,000028:
047658,000029: # R-TO-RP,ARCTAN,SETGAMMA,SETRE
047659,000030: # ERASABLE INIT. REQ.
047660,000031:
047661,000032: # AXO,-AYO,AZO,TEPHEM (SET AT LAUNCH TIME)
047662,000033: # ALPHAV = POSITION VECTOR METERS B-29
047663,000034: # MPAC-- TIME (CSECS B-28)
047664,000035: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047665,000036: # LUNAFLAG=0 FOR EARTH,1 FOR MOON
047666,000037: # OUTPUT
047667,000038:
047668,000039: # LATITUDE IN LAT (REVS. B-0)
047669,000040: # LONGITUDE IN LONG (REVS. B-0)
047670,000041: # ALTITUDE IN ALT METERS B-29
047671,000042: 30,3760 BANK 30
047672,000043: 13,2000 SETLOC LATLONG
047673,000044: 13,2000 BANK
047674,000045:
047675,000046: 13,2347 COUNT* $$/LT-LG
047676,000047: 13,2347 E4,1431 EBANK= ALPHAV
047677,000048: 13,2347 40220 LAT-LONG STQ SETPD
047678,000049: 13,2350 03674 INCORPEX
047679,000050: 13,2351 00001 0D
047680,000051: 13,2352 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
047681,000052: 13,2353 02032 ALPHAV
047682,000053: 13,2354 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
047683,000054: 13,2355 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
047684,000055: 13,2356 24007 ZEROVEC # SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047685,000056: 13,2357 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
047686,000057: 13,2360 01743 LUNAFLAG # 0=EARTH,1=MOON
047687,000058: 13,2361 26362 CALLRTRP
047688,000059: 13,2362 77624 CALLRTRP CALL
047689,000060: 13,2363 51642 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
047690,000061: 13,2364 77656 UNIT # UNIT RP B-1
047691,000062: 13,2365 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
047692,000063: 13,2366 26546 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH,=1 FOR MOON
047693,000064: 13,2367 77624 CALL # SCALED B-1
047694,000065: 13,2370 26556 SETRE # CALC RE METERS B-29
047695,000066: 13,2371 63545 DLOAD DSQ
047696,000067: 13,2372 02032 ALPHAV
047697,000068: 13,2373 63525 PDDL DSQ
047698,000069: 13,2374 02034 ALPHAV +2
047699,000070: 13,2375 75415 DAD SQRT
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Page 1125
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047701,000072: 13,2376 76405 DMP SL1R
047702,000073: 13,2377 00011 GAMRP
047703,000074: 13,2400 14021 STODL COSTH # COS(LAT) B-1
047704,000075: 13,2401 02036 ALPHAV +4
047705,000076: 13,2402 34023 STCALL SINTH # SIN(LAT) B-1
047706,000077: 13,2403 26506 ARCTAN
047707,000078: 13,2404 15120 STODL LAT # LAT B0
047708,000079: 13,2405 02032 ALPHAV
047709,000080: 13,2406 14021 STODL COSTH # COS(LONG) B-1
047710,000081: 13,2407 02034 ALPHAV +2
047711,000082: 13,2410 34023 STCALL SINTH # SIN(LONG) B-1
047712,000083: 13,2411 26506 ARCTAN
047713,000084: 13,2412 15122 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047714,000085: 13,2413 02070 ALPHAM
047715,000086: 13,2414 77625 DSU # ALT= R-RE METERS B-29
047716,000087: 13,2415 03673 ERADM
047717,000088: 13,2416 35124 STCALL ALT # EXIT WITH ALT METERS B-29
047718,000089: 13,2417 03674 INCORPEX
047719,000090:
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Page 1126
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047721,000092: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047722,000093: # CALLING SEQUENCE
047723,000094:
047724,000095: # L-1 CALL
047725,000096: # L LALOTORV
047726,000097: # SUBROUTINES USED
047727,000098:
047728,000099: # SETGAMMA,SETRE,RP-TO-R
047729,000100: # ERASABLE INIT. REQ.
047730,000101:
047731,000102: # AXO,AYO,AZO,TEPHEM SET AT LAUNCH TIME
047732,000103: # LAT-- LATITUDE (REVS B0)
047733,000104: # LONG-- LONGITUDE (REVS B0)
047734,000105: # ALT--ALTITUDE (METERS) B-29
047735,000106: # MPAC-- TIME (CSECS B-28)
047736,000107: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047737,000108: # LUNAFLAG=0 FOR EARTH,1 FOR MOON
047738,000109: # OUTPUT
047739,000110:
047740,000111: # R-VECTOR IN ALPHAV (METERS B-29)
047741,000112: 13,2420 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
047742,000113: 13,2421 03674 INCORPEX
047743,000114: 13,2422 00001 0D
047744,000115: 13,2423 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
047745,000116: 13,2424 26546 SETGAMMA # GAMMA=B2/A2 FOR EARTH,1 FOR MOON B-1
047746,000117: 13,2425 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
047747,000118: 13,2426 01120 LAT # UNIT RP= SIN(LONG)COS(LAT) 2-3D
047748,000119: 13,2427 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
047749,000120: 13,2430 00011 GAMRP
047750,000121: 13,2431 01120 LAT # 0-1D= GAMMA*SIN(LAT) B-2
047751,000122: 13,2432 65346 COS PDDL # PD4 2-3D=COS(LAT) B-1 TEMPORARILY
047752,000123: 13,2433 01122 LONG
047753,000124: 13,2434 57356 SIN DMPR # PD 2
047754,000125: 13,2435 71525 PDDL COS # PD 4 2-3D=SIN(LONG)COS(LAT) B-2
047755,000126: 13,2436 01120 LAT
047756,000127: 13,2437 71525 PDDL COS # PD 6 4-5D=COS(LAT) B-1 TEMPORARILY
047757,000128: 13,2440 01122 LONG
047758,000129: 13,2441 55475 DMPR VDEF # PD 4 MPAC= COS(LONG)COS(LAT) B-2
047759,000130: 13,2442 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
047760,000131: 13,2443 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
047761,000132: 13,2444 26556 SETRE # RE METERS B-29
047762,000133: 13,2445 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047763,000134: 13,2446 24007 ZEROVEC
047764,000135: 13,2447 01743 LUNAFLAG
047765,000136: 13,2450 26452 CALLRPRT
047766,000137: 13,2451 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
047767,000138: 13,2452 77624 CALLRPRT CALL
047768,000139: 13,2453 55720 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
047769,000140: 13,2454 16032 STODL ALPHAV
047770,000141: 13,2455 03673 ERADM
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Page 1127
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047772,000143: 13,2456 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
047773,000144: 13,2457 01124 ALT
047774,000145: 13,2460 02032 ALPHAV
047775,000146: 13,2461 77772 VSL1 # R METERS B-29
047776,000147: 13,2462 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
047777,000148: 13,2463 03674 INCORPEX
047778,000149: # SUBROUTINE TO COMPUTE EARTH RADIUS
047779,000150:
047780,000151: # INPUT
047781,000152:
047782,000153: # 1/2 SIN LAT IN ALPHAV +4
047783,000154:
047784,000155: # OUTPUT
047785,000156:
047786,000157: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047787,000158:
047788,000159: 13,2464 63545 GETERAD DLOAD DSQ
047789,000160: 13,2465 02036 ALPHAV +4 # SIN**2(L)
047790,000161: 13,2466 44352 SL1 BDSU
047791,000162: 13,2467 24005 DP1/2 # COS**2(L)
047792,000163: 13,2470 44275 DMPR BDSU
047793,000164: 13,2471 26505 EE
047794,000165: 13,2472 24005 DP1/2
047795,000166: 13,2473 75465 BDDV SQRT
047796,000167: 13,2474 26501 B2XSC
047797,000168: 13,2475 77622 SR4R
047798,000169: 13,2476 03673 STORE ERADM
047799,000170: 13,2477 77616 RVQ
047800,000171:
047801,000172: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166,B=6356784 METERS
047802,000173: # B2XSC= B**2 SCALED B-51
047803,000174: # B2/A2= B**2/A**2 SCALED B-1
047804,000175: # EE=(1-B**2/A**2) SCALED B-0
047805,000176: 13,2500 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
047806,000177:
047807,000178: 13,2502 12,2004 DP1/2 = XUNIT
047808,000179: 13,2502 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
047809,000180:
047810,000181: 13,2504 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
047811,000182:
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Page 1128
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047813,000184: # ARCTAN SUBROUTINE
047814,000185:
047815,000186:
047816,000187: # CALLING SEQUENCE
047817,000188:
047818,000189: # SIN THETA IN SINTH B-1
047819,000190: # COS THETA IN COSTH B-1
047820,000191: # CALL ARCTAN
047821,000192:
047822,000193: # OUTPUT
047823,000194: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047824,000195:
047825,000196:
047826,000197: 13,2506 77600 ARCTAN BOV
047827,000198: 13,2507 26510 CLROVFLW
047828,000199: 13,2510 63545 CLROVFLW DLOAD DSQ
047829,000200: 13,2511 00023 SINTH
047830,000201: 13,2512 63525 PDDL DSQ
047831,000202: 13,2513 00021 COSTH
047832,000203: 13,2514 77615 DAD
047833,000204: 13,2515 75454 BZE SQRT
047834,000205: 13,2516 26534 ARCTANXX # ATAN=0/0 SET THETA=0
047835,000206: 13,2517 40065 BDDV BOV
047836,000207: 13,2520 00023 SINTH
047837,000208: 13,2521 26541 ATAN=90
047838,000209: 13,2522 67542 SR1 ASIN
047839,000210: 13,2523 00025 STORE THETA
047840,000211: 13,2524 50125 PDDL BMN
047841,000212: 13,2525 00021 COSTH
047842,000213: 13,2526 26530 NEGCOS
047843,000214: 13,2527 43545 DLOAD RVQ
047844,000215: 13,2530 57545 NEGCOS DLOAD DCOMP
047845,000216: 13,2531 43244 BPL DAD
047846,000217: 13,2532 26536 NEGOUT
047847,000218: 13,2533 24005 DP1/2
047848,000219: 13,2534 00025 ARCTANXX STORE THETA
047849,000220: 13,2535 77616 RVQ
047850,000221:
047851,000222: 13,2536 52025 NEGOUT DSU GOTO
047852,000223: 13,2537 24005 DP1/2
047853,000224: 13,2540 26534 ARCTANXX
047854,000225: 13,2541 75345 ATAN=90 DLOAD SIGN
047855,000226: 13,2542 11011 LODP1/4
047856,000227: 13,2543 00023 SINTH
047857,000228: 13,2544 00025 STORE THETA
047858,000229: 13,2545 77616 RVQ
047859,000230:
047860,000231: 13,2546 12,2006 2DZERO = DPZERO
047861,000232:
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Page 1129
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047863,000234: # ..... SETGAMMA SUBROUTINE .....
047864,000235: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047865,000236:
047866,000237: # GAMMA = B**2/A**2 FOR EARTH (B-1)
047867,000238: # GAMMA = 1 FOR MOON (B-1)
047868,000239:
047869,000240: # CALLING SEQUENCE
047870,000241: # L CALL
047871,000242: # L+1 SETGAMMA
047872,000243:
047873,000244: # INPUT
047874,000245: # LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047875,000246:
047876,000247: # OUTPUT
047877,000248: # GAMMA IN GAMRP (B-1)
047878,000249:
047879,000250: 13,2546 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
047880,000251: 13,2547 26503 B2/A2 # EARTH GAMMA
047881,000252: 13,2550 01743 LUNAFLAG
047882,000253: 13,2551 26554 SETGMEX
047883,000254: 13,2552 77735 SLOAD
047884,000255: 13,2553 24005 1B1 # MOON GAMMA
047885,000256: 13,2554 00011 SETGMEX STORE GAMRP
047886,000257: 13,2555 77616 RVQ
047887,000258: 13,2556 GAMRP = 8D
047888,000259:
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Page 1130
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047890,000261: # .....SETRE SUBROUTINE .....
047891,000262: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047892,000263:
047893,000264: # RE= RM FOR MOON
047894,000265: # RE= RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047895,000266:
047896,000267: # CALLING SEQUENCE
047897,000268: # L CALL
047898,000269: # L+1 SETRE
047899,000270:
047900,000271: # SUBROUTINES USED
047901,000272: # GETERAD
047902,000273:
047903,000274: # INPUT
047904,000275: # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED RE
047905,000276: # ALPHAV +4= 1/2 SINL IF GETERAD IS CALLED
047906,000277: # LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047907,000278:
047908,000279: # OUTPUT
047909,000280: # ERADM= 504RM FOR MOON (METERS B-29)
047910,000281: # ERADM= ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047911,000282:
047912,000283: 13,2556 71220 SETRE STQ DLOAD
047913,000284: 13,2557 00051 SETREX
047914,000285: 13,2560 10003 504RM
047915,000286: 13,2561 71214 BON DLOAD # BRANCH FOR MOON
047916,000287: 13,2562 01703 LUNAFLAG
047917,000288: 13,2563 26573 TSTRLSRM
047918,000289: 13,2564 10001 ERAD
047919,000290: 13,2565 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE,1 FOR COMPUTED
047920,000291: 13,2566 00742 ERADFLAG
047921,000292: 13,2567 26571 SETRXX
047922,000293: 13,2570 26464 GETERAD
047923,000294: 13,2571 37673 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
047924,000295: 13,2572 00051 SETREX
047925,000296: 13,2573 77214 TSTRLSRM BON VLOAD # ERADFLAG=0,SET R0=RLS
047926,000297: 13,2574 00702 ERADFLAG # =1 R0=RM
047927,000298: 13,2575 26571 SETRXX
047928,000299: 13,2576 02021 RLS
047929,000300: 13,2577 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
047930,000301: 13,2600 77650 GOTO
047931,000302: 13,2601 26571 SETRXX
047932,000303: 13,2602 0000051 SETREX = S2
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc