GAP: ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091 17:53 DEC. 19, 1969Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together.
Source Code
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This source code is very close to the Apollo Guidance Computer software for the
Apollo 13 Lunar module. This revision of the Luminary 131 program is from December
of 1969, whereas there was a later revision in January of 1970, and still another
revision in February, which is the code that flew on the mission.
As far as this transcription is concerned, it was originally from a copy made in 1991 of
a printout from the collection of AGC developer Don Eyles for collector David Craig.
It was subsequently scanned by Gary Neff, reprocessed for online
presentation at the now-discontinued History of Recent Science and Technology (HRST) website
of MIT's Dibner Institute (the full-quality scans being discarded in the process),
and finally transcribed by Ron Burkey for the Virtual AGC Project. Although a
high-quality replacement scan for a completely illegible page was later provided by Gary
Neff, the reduced legibility of the reprocessed HRST posting nevertheless caused many
errors to be introduced into the transcription. Accordingly, a second scan of the same physical
printout was made in 2017 for the Virtual AGC Project's collection at the Internet Archive,
and used to correct the transcription errors. All of the scanned materials mentioned,
as well as other Luminary 131 related material, are available online.
Don Eyles apprently made additional hand-written notes in printout between 1991 and 2017,
so the two scans are not identical in that respect. The page-headings in the printout read, in part:GAP: ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091 17:53 DEC. 19, 1969Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together. |
047218,000002: ## Copyright: Public domain.
047219,000003: ## Filename: LATITUDE_LONGITUDE_SUBROUTINES.agc
047220,000004: ## Purpose: A section of Luminary 1C, revision 131.
047221,000005: ## It is part of the source code for the Lunar Module's (LM)
047222,000006: ## Apollo Guidance Computer (AGC) for Apollo 13.
047223,000007: ## This file is intended to be a faithful transcription, except
047224,000008: ## that the code format has been changed to conform to the
047225,000009: ## requirements of the yaYUL assembler rather than the
047226,000010: ## original YUL assembler.
047227,000011: ## Reference: pp. 1127-1133
047228,000012: ## Contact: Ron Burkey <info@sandroid.org>.
047229,000013: ## Website: www.ibiblio.org/apollo/index.html
047230,000014: ## Mod history: 05/31/03 RSB. Began transcribing.
047231,000015: ## 05/14/05 RSB Corrected website reference above.
047232,000016: ## 2011-01-05 JL Fixed indentation of RVQ instruction.
047233,000017: ## 2017-01-06 RSB Page numbers now agree with those on the
047234,000018: ## original harcopy, as opposed to the PDF page
047235,000019: ## numbers in 1701.pdf.
047236,000020: ## 2017-02-05 RSB Back-ported comment corrections
047237,000021: ## identified while proofing Artemis 072.
047238,000022: ## 2017-02-27 RSB Proofed comment text using octopus/ProoferComments.
047239,000023: ## 2017-03-13 RSB Comment-text fixes noted in proofing Luminary 116.
047240,000024: ## 2017-03-15 RSB Comment-text fixes identified in 5-way
047241,000025: ## side-by-side diff of Luminary 69/99/116/131/210.
047242,000026:
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Page 1127 |
047244,000028: # SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047245,000029:
047246,000030: # CALLING SEQUENCE
047247,000031: # L-1 CALL
047248,000032: # L LAT-LONG
047249,000033:
047250,000034: # SUBROUTINES USED
047251,000035: # R-TO-RP, ARCTAN, SETGAMMA, SETRE
047252,000036:
047253,000037: # ERASABLE INIT. REQ.
047254,000038: # AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
047255,000039: # ALPHAV = POSITION VECTOR METERS B-29
047256,000040: # MPAC -- TIME (CSECS B-28)
047257,000041: # ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047258,000042: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047259,000043:
047260,000044: # OUTPUT
047261,000045: # LATITUDE IN LAT (REVS. B-0)
047262,000046: # LONGITUDE IN LONG (REVS. B-0)
047263,000047: # ALTITUDE IN ALT METERS B-29
047264,000048:
047265,000049: 30,3766 BANK 30
047266,000050: 13,2000 SETLOC LATLONG
047267,000051: 13,2000 BANK
047268,000052:
047269,000053: 13,2347 COUNT* $$/LT-LG
047270,000054: 13,2347 E4,1431 EBANK= ALPHAV
047271,000055: 13,2347 40220 LAT-LONG STQ SETPD
047272,000056: 13,2350 03674 INCORPEX
047273,000057: 13,2351 00001 0D
047274,000058: 13,2352 24007 STOVL 6D # SAVE TIME IN 6-7D FOR R-TO-RP
047275,000059: 13,2353 02032 ALPHAV
047276,000060: 13,2354 51406 PUSH ABVAL # 0-5D= R FOR R-TO-RP
047277,000061: 13,2355 16070 STODL ALPHAM # ABS. VALUE OF R FOR ALT FORMULA BELOW
047278,000062: 13,2356 24007 ZEROVEC # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047279,000063: 13,2357 71414 BOFF COS # USE COS(0) TO GET NON-ZERO IN MPAC
047280,000064: 13,2360 01743 LUNAFLAG # 0=EARTH, 1=MOON
047281,000065: 13,2361 26362 CALLRTRP
047282,000066: 13,2362 77624 CALLRTRP CALL
047283,000067: 13,2363 51700 R-TO-RP # RP VECTOR CONVERTED FROM R B-29
047284,000068: 13,2364 77656 UNIT # UNIT RP B-1
047285,000069: 13,2365 36032 STCALL ALPHAV # U2= 1/2 SINL FOR SETRE SUBR BELOW
047286,000070: 13,2366 26546 SETGAMMA # SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
047287,000071: 13,2367 77624 CALL # SCALED B-1
047288,000072: 13,2370 26556 SETRE # CALC RE METERS B-29
047289,000073: 13,2371 63545 DLOAD DSQ
047290,000074: 13,2372 02032 ALPHAV
047291,000075: 13,2373 63525 PDDL DSQ
047292,000076: 13,2374 02034 ALPHAV +2
047293,000077: 13,2375 75415 DAD SQRT
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Page 1128 |
047295,000079: 13,2376 76405 DMP SL1R
047296,000080: 13,2377 00011 GAMRP
047297,000081: 13,2400 14021 STODL COSTH # COS(LAT) B-1
047298,000082: 13,2401 02036 ALPHAV +4
047299,000083: 13,2402 34023 STCALL SINTH # SIN(LAT) B-1
047300,000084: 13,2403 26506 ARCTAN
047301,000085: 13,2404 15120 STODL LAT # LAT B0
047302,000086: 13,2405 02032 ALPHAV
047303,000087: 13,2406 14021 STODL COSTH # COS(LONG) B-1
047304,000088: 13,2407 02034 ALPHAV +2
047305,000089: 13,2410 34023 STCALL SINTH # SIN(LONG) B-1
047306,000090: 13,2411 26506 ARCTAN
047307,000091: 13,2412 15122 STODL LONG # LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047308,000092: 13,2413 02070 ALPHAM
047309,000093: 13,2414 77625 DSU # ALT= R-RE METERS B-29
047310,000094: 13,2415 03673 ERADM
047311,000095: 13,2416 35124 STCALL ALT # EXIT WITH ALT METERS B-29
047312,000096: 13,2417 03674 INCORPEX
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Page 1129 |
047314,000098: # SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047315,000099:
047316,000100: # CALLING SEQUENCE
047317,000101: # L-1 CALL
047318,000102: # L LALOTORV
047319,000103:
047320,000104: # SUBROUTINES USED
047321,000105: # SETGAMMA, SETRE, RP-TO-R
047322,000106:
047323,000107: # ERASABLE INIT. REQ.
047324,000108: # AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
047325,000109: # LAT -- LATITUDE (REVS B0)
047326,000110: # LONG -- LONGITUDE (REVS B0)
047327,000111: # ALT -- ALTITUDE (METERS) B-29
047328,000112: # MPAC -- TIME (CSECS B-28)
047329,000113: # ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047330,000114: # LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047331,000115:
047332,000116: # OUTPUT
047333,000117: # R-VECTOR IN ALPHAV (METERS B-29)
047334,000118:
047335,000119: 13,2420 40220 LALOTORV STQ SETPD # LAT,LONG,ALT TO R VECTOR
047336,000120: 13,2421 03674 INCORPEX
047337,000121: 13,2422 00001 0D
047338,000122: 13,2423 34007 STCALL 6D # 6-7D= TIME FOR RP-TO-R
047339,000123: 13,2424 26546 SETGAMMA # GAMMA=B2/A2 FOR EARTH, 1 FOR MOON B-1
047340,000124: 13,2425 73545 DLOAD SIN # COS(LONG)COS(LAT) IN MPAC
047341,000125: 13,2426 01120 LAT # UNIT RP = SIN(LONG)COS(LAT) 2-3D
047342,000126: 13,2427 65275 DMPR PDDL # PD 2 GAMMA*SIN(LAT) 0-1D
047343,000127: 13,2430 00011 GAMRP
047344,000128: 13,2431 01120 LAT # 0-1D= GAMMA*SIN(LAT) B-2
047345,000129: 13,2432 65346 COS PDDL # PD4 2-3D= COS(LAT) B-1 TEMPORARILY
047346,000130: 13,2433 01122 LONG
047347,000131: 13,2434 57356 SIN DMPR # PD 2
047348,000132: 13,2435 71525 PDDL COS # PD 4 2-3D = SIN(LONG)COS(LAT) B-2
047349,000133: 13,2436 01120 LAT
047350,000134: 13,2437 71525 PDDL COS # PD 6 4-5D = COS(LAT) B-1 TEMPORARILY
047351,000135: 13,2440 01122 LONG
047352,000136: 13,2441 55475 DMPR VDEF # PD4 MPAC= COS(LONG)COS(LAT) B-2
047353,000137: 13,2442 41456 UNIT PUSH # 0-5D= UNIT RP FOR RP-TO-R SUBR.
047354,000138: 13,2443 36032 STCALL ALPHAV # ALPHAV +4= SINL FOR SETRE SUBR.
047355,000139: 13,2444 26556 SETRE # RE METERS B-29
047356,000140: 13,2445 43145 DLOAD BOFF # SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047357,000141: 13,2446 24007 ZEROVEC
047358,000142: 13,2447 01743 LUNAFLAG
047359,000143: 13,2450 26452 CALLRPRT
047360,000144: 13,2451 77746 COS # USE COS(0) TO GET NON-ZERO IN MPAC
047361,000145: 13,2452 77624 CALLRPRT CALL
047362,000146: 13,2453 55716 RP-TO-R # EXIT WITH UNIT R VECTOR IN MPAC
047363,000147: 13,2454 16032 STODL ALPHAV
047364,000148: 13,2455 03673 ERADM
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Page 1130 |
047366,000150: 13,2456 74215 DAD VXSC # (RE + ALT)(UNIT R) METERS B-30
047367,000151: 13,2457 01124 ALT
047368,000152: 13,2460 02032 ALPHAV
047369,000153: 13,2461 77772 VSL1 # R METERS B-29
047370,000154: 13,2462 36032 STCALL ALPHAV # EXIT WITH R IN METERS B-29
047371,000155: 13,2463 03674 INCORPEX
047372,000156:
047373,000157: # SUBROUTINE TO COMPUTE EARTH RADIUS
047374,000158:
047375,000159: # INPUT
047376,000160: # 1/2 SIN LAT IN ALPHAV +4
047377,000161:
047378,000162: # OUTPUT
047379,000163: # EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047380,000164:
047381,000165: 13,2464 63545 GETERAD DLOAD DSQ
047382,000166: 13,2465 02036 ALPHAV +4 # SIN**2(L)
047383,000167: 13,2466 44352 SL1 BDSU
047384,000168: 13,2467 24005 DP1/2 # COS**2(L)
047385,000169: 13,2470 44275 DMPR BDSU
047386,000170: 13,2471 26505 EE
047387,000171: 13,2472 24005 DP1/2
047388,000172: 13,2473 75465 BDDV SQRT
047389,000173: 13,2474 26501 B2XSC
047390,000174: 13,2475 77622 SR4R
047391,000175: 13,2476 03673 STORE ERADM
047392,000176: 13,2477 77616 RVQ
047393,000177:
047394,000178: # THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
047395,000179: # B2XSC = B**2 SCALED B-51
047396,000180: # B2/A2 = B**2/A**2 SCALED B-1
047397,000181: # EE = (1-B**2/A**2) SCALED B-0
047398,000182:
047399,000183: 13,2500 00446 00305 B2XSC 2DEC .0179450689 # B**2 SCALED B-51
047400,000184: 13,2502 12,2004 DP1/2 = XUNIT
047401,000185: 13,2502 17711 05254 B2/A2 2DEC .9933064884 B-1 # GAMMA= B**2/A**2 B-1
047402,000186: 13,2504 00155 25250 EE 2DEC 6.6935116 E-3 # (1-B**2/A**2) B-0
047403,000187:
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Page 1131 |
047405,000189: # ARCTAN SUBROUTINE
047406,000190:
047407,000191: # CALLING SEQUENCE
047408,000192: # SIN THETA IN SINTH B-1
047409,000193: # COS THETA IN COSTH B-1
047410,000194: # CALL ARCTAN
047411,000195:
047412,000196: # OUTPUT
047413,000197: # ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047414,000198:
047415,000199: 13,2506 77600 ARCTAN BOV
047416,000200: 13,2507 26510 CLROVFLW
047417,000201: 13,2510 63545 CLROVFLW DLOAD DSQ
047418,000202: 13,2511 00023 SINTH
047419,000203: 13,2512 63525 PDDL DSQ
047420,000204: 13,2513 00021 COSTH
047421,000205: 13,2514 77615 DAD
047422,000206: 13,2515 75454 BZE SQRT
047423,000207: 13,2516 26534 ARCTANXX # ATAN=0/0 SET THETA=0
047424,000208: 13,2517 40065 BDDV BOV
047425,000209: 13,2520 00023 SINTH
047426,000210: 13,2521 26541 ATAN=90
047427,000211: 13,2522 67542 SR1 ASIN
047428,000212: 13,2523 00025 STORE THETA
047429,000213: 13,2524 50125 PDDL BMN
047430,000214: 13,2525 00021 COSTH
047431,000215: 13,2526 26530 NEGCOS
047432,000216: 13,2527 43545 DLOAD RVQ
047433,000217: 13,2530 57545 NEGCOS DLOAD DCOMP
047434,000218: 13,2531 43244 BPL DAD
047435,000219: 13,2532 26536 NEGOUT
047436,000220: 13,2533 24005 DP1/2
047437,000221: 13,2534 00025 ARCTANXX STORE THETA
047438,000222: 13,2535 77616 RVQ
047439,000223:
047440,000224: 13,2536 52025 NEGOUT DSU GOTO
047441,000225: 13,2537 24005 DP1/2
047442,000226: 13,2540 26534 ARCTANXX
047443,000227: 13,2541 75345 ATAN=90 DLOAD SIGN
047444,000228: 13,2542 11003 LODP1/4
047445,000229: 13,2543 00023 SINTH
047446,000230: 13,2544 00025 STORE THETA
047447,000231: 13,2545 77616 RVQ
047448,000232:
047449,000233: 13,2546 12,2006 2DZERO = DPZERO
047450,000234:
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Page 1132 |
047452,000236: # ..... SETGAMMA SUBROUTINE .....
047453,000237: # SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047454,000238:
047455,000239: # GAMMA = B**2/A**2 FOR EARTH (B-1)
047456,000240: # GAMMA = 1 FOR MOON (B-1)
047457,000241:
047458,000242: # CALLING SEQUENCE
047459,000243: # L CALL
047460,000244: # L+1 SETGAMMA
047461,000245:
047462,000246: # INPUT
047463,000247: # LUNAFLAG=0 FOR EARTH, =1 FOR MOON
047464,000248:
047465,000249: # OUTPUT
047466,000250: # GAMMA IN GAMRP (B-1)
047467,000251:
047468,000252: 13,2546 43145 SETGAMMA DLOAD BOFF # BRANCH FOR EARTH
047469,000253: 13,2547 26503 B2/A2 # EARTH GAMMA
047470,000254: 13,2550 01743 LUNAFLAG
047471,000255: 13,2551 26554 SETGMEX
047472,000256: 13,2552 77735 SLOAD
047473,000257: 13,2553 24005 1B1 # MOON GAMMA
047474,000258: 13,2554 00011 SETGMEX STORE GAMRP
047475,000259: 13,2555 77616 RVQ
047476,000260: 13,2556 GAMRP = 8D
047477,000261:
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Page 1133 |
047479,000263: # ..... SETRE SUBROUTINE .....
047480,000264: # SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047481,000265:
047482,000266: # RE = RM FOR MOON
047483,000267: # RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047484,000268:
047485,000269: # CALLING SEQUENCE
047486,000270: # L CALL
047487,000271: # L+1 SETRE
047488,000272:
047489,000273: # SUBROUTINES USED
047490,000274: # GETERAD
047491,000275:
047492,000276: # INPUT
047493,000277: # ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
047494,000278: # ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
047495,000279: # LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
047496,000280:
047497,000281: # OUTPUT
047498,000282: # ERADM = 504RM FOR MOON (METERS B-29)
047499,000283: # ERADM = ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047500,000284:
047501,000285: 13,2556 71220 SETRE STQ DLOAD
047502,000286: 13,2557 00051 SETREX
047503,000287: 13,2560 10003 504RM
047504,000288: 13,2561 71214 BON DLOAD # BRANCH FOR MOON
047505,000289: 13,2562 01703 LUNAFLAG
047506,000290: 13,2563 26573 TSTRLSRM
047507,000291: 13,2564 10001 ERAD
047508,000292: 13,2565 45014 BOFF CALL # ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
047509,000293: 13,2566 00742 ERADFLAG
047510,000294: 13,2567 26571 SETRXX
047511,000295: 13,2570 26464 GETERAD
047512,000296: 13,2571 37673 SETRXX STCALL ERADM # EXIT WITH RE OR RM METERS B-29
047513,000297: 13,2572 00051 SETREX
047514,000298: 13,2573 77214 TSTRLSRM BON VLOAD # ERADFLAG=0, SET R0=RLS
047515,000299: 13,2574 00702 ERADFLAG # =1 R0=RM
047516,000300: 13,2575 26571 SETRXX
047517,000301: 13,2576 02023 RLS
047518,000302: 13,2577 64446 ABVAL SR2R # SCALE FROM B-27 TO B-29
047519,000303: 13,2600 77650 GOTO
047520,000304: 13,2601 26571 SETRXX
047521,000305: 13,2602 0000051 SETREX = S2
047522,000306:
047523,000307:
End of include-file LATITUDE_LONGITUDE_SUBROUTINES.agc. Parent file is MAIN.agc