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. |
052306,000002: ## Copyright: Public domain.
052307,000003: ## Filename: INFLIGHT_ALIGNMENT_ROUTINES.agc
052308,000004: ## Purpose: A section of Luminary 1C, revision 131.
052309,000005: ## It is part of the source code for the Lunar Module's (LM)
052310,000006: ## Apollo Guidance Computer (AGC) for Apollo 13.
052311,000007: ## This file is intended to be a faithful transcription, except
052312,000008: ## that the code format has been changed to conform to the
052313,000009: ## requirements of the yaYUL assembler rather than the
052314,000010: ## original YUL assembler.
052315,000011: ## Reference: pp. 1241-1250
052316,000012: ## Contact: Ron Burkey <info@sandroid.org>.
052317,000013: ## Website: www.ibiblio.org/apollo/index.html
052318,000014: ## Mod history: 06/03/03 RSB. Began transcribing.
052319,000015: ## 05/14/05 RSB. Corrected website reference above.
052320,000016: ## 2017-01-06 RSB Page numbers now agree with those on the
052321,000017: ## original hardcopy, as opposed to the PDF page
052322,000018: ## numbers in 1701.pdf.
052323,000019: ## 2017-02-27 RSB Proofed comment text using octopus/ProoferComments.
052324,000020: ## 2017-03-17 RSB Comment-text fixes identified in diff'ing
052325,000021: ## Luminary 99 vs Comanche 55.
052326,000022:
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Page 1241 |
052328,000024: 22,3773 BANK 22
052329,000025: 23,2000 SETLOC INFLIGHT
052330,000026: 23,2000 BANK
052331,000027:
052332,000028: 23,3251 E5,1642 EBANK= XSM
052333,000029:
052334,000030: # CALCGTA COMPUTES THE GYRO TORQUE ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
052335,000031:
052336,000032: # THE INPUT IS THE DESIRED STABLE MEMBER COORDINATES REFERRED TO PRESENT STABLE MEMBER COORDINATES. THE THREE
052337,000033: # HALF-UNIT VECTORS ARE STORED AT XDC, YDC, AND ZDC.
052338,000034:
052339,000035: # THE OUTPUTS ARE THE THREE GYRO TORQUING ANGLES TO BE APPLIED TO THE Y, Z, AND X GYROS AND ARE STORED DP AT IGC,
052340,000036: # MGC, AND OGC RESPECTIVELY.
052341,000037:
052342,000038: 23,3251 COUNT* $$/INFLT
052343,000039: 23,3251 71220 CALCGTA ITA DLOAD # PUSHDOWN 00-03, 16D-27D, 34D-37D
052344,000040: 23,3252 00051 S2 # XDC = (XD1 XD2 XD3)
052345,000041: 23,3253 02665 XDC # YDC = (YD1 YD2 YD3)
052346,000042: 23,3254 65325 PDDL PDDL # ZDC = (ZD1 ZD2 ZD3)
052347,000043: 23,3255 06524 HI6ZEROS
052348,000044: 23,3256 02671 XDC +4
052349,000045: 23,3257 55476 DCOMP VDEF
052350,000046: 23,3260 77656 UNIT
052351,000047: 23,3261 14027 STODL ZPRIME # ZP = UNIT(-XD3 0 XD1) = (ZP1 ZP2 ZP3)
052352,000048: 23,3262 00027 ZPRIME
052353,000049:
052354,000050: 23,3263 77742 SR1
052355,000051: 23,3264 14023 STODL SINTH # SIN(IGC) = ZP1
052356,000052: 23,3265 00033 ZPRIME +4
052357,000053: 23,3266 77742 SR1
052358,000054: 23,3267 34021 STCALL COSTH # COS(IGC) = ZP3
052359,000055: 23,3270 47322 ARCTRIG
052360,000056:
052361,000057: 23,3271 16742 STODL IGC # Y GYRO TORQUING ANGLE FRACTION OF REV.
052362,000058: 23,3272 02667 XDC +2
052363,000059: 23,3273 77742 SR1
052364,000060: 23,3274 14023 STODL SINTH # SIN(MGC) = XD2
052365,000061: 23,3275 00027 ZPRIME
052366,000062:
052367,000063: 23,3276 65205 DMP PDDL
052368,000064: 23,3277 02671 XDC +4 # PD00 = (ZP1)(XD3)
052369,000065: 23,3300 00033 ZPRIME +4
052370,000066:
052371,000067: 23,3301 45205 DMP DSU
052372,000068: 23,3302 02665 XDC # MPAC = (ZP3)(XD1)
052373,000069: 23,3303 77626 STADR
052374,000070: 23,3304 43756 STCALL COSTH # COS(MGC) = MPAC - PD00
052375,000071: 23,3305 47322 ARCTRIG
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Page 1242 |
052377,000073: 23,3306 26744 STOVL MGC # Z GYRO TORQUING ANGLE FRACTION OF REV.
052378,000074: 23,3307 00027 ZPRIME
052379,000075: 23,3310 77641 DOT
052380,000076: 23,3311 02701 ZDC
052381,000077: 23,3312 24021 STOVL COSTH # COS(OGC) = ZP . ZDC
052382,000078: 23,3313 00027 ZPRIME
052383,000079: 23,3314 77641 DOT
052384,000080: 23,3315 02673 YDC
052385,000081: 23,3316 34023 STCALL SINTH # SIN(OGC) = ZP . YDC
052386,000082: 23,3317 47322 ARCTRIG
052387,000083:
052388,000084: 23,3320 36740 STCALL OGC # X GYRO TORQUING ANGLE FRACTION OF REV.
052389,000085: 23,3321 00051 S2
052390,000086:
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Page 1243 |
052392,000088: # ARCTRIG COMPUTES AN ANGLE GIVEN THE SINE AND COSINE OF THIS ANGLE.
052393,000089:
052394,000090: # THE INPUTS ARE SIN/4 AND COS/4 STORED DP AT SINTH AND COSTH.
052395,000091:
052396,000092: # THE OUTPUT IS THE CALCULATED ANGLE BETWEEN +.5 AND -.5 REVOLUTIONS AND STORED AT THETA. THE OUTPUT IS ALSO
052397,000093: # AVAILABLE AT MPAC.
052398,000094:
052399,000095: 23,3322 51545 ARCTRIG DLOAD ABS # PUSHDOWN 16D-21D
052400,000096: 23,3323 00023 SINTH
052401,000097: 23,3324 50025 DSU BMN
052402,000098: 23,3325 07536 QTSN45 # ABS(SIN/4) - SIN(45)/4
052403,000099: 23,3326 47335 TRIG1 # IF (-45,45) OR (135,-135)
052404,000100:
052405,000101: 23,3327 72545 DLOAD SL1 # (45,135) OR (-135,-45)
052406,000102: 23,3330 00021 COSTH
052407,000103: 23,3331 75326 ACOS SIGN
052408,000104: 23,3332 00023 SINTH
052409,000105: 23,3333 00025 STORE THETA # X = ARCCOS(COS) WITH SIGN(SIN)
052410,000106: 23,3334 77616 RVQ
052411,000107:
052412,000108: 23,3335 72545 TRIG1 DLOAD SL1 # (-45,45) OR (135,-135)
052413,000109: 23,3336 00023 SINTH
052414,000110: 23,3337 77736 ASIN
052415,000111: 23,3340 14025 STODL THETA # X = ARCSIN(SIN) WITH SIGN(SIN)
052416,000112: 23,3341 00021 COSTH
052417,000113: 23,3342 77640 BMN
052418,000114: 23,3343 47346 TRIG2 # IF (135,-135)
052419,000115:
052420,000116: 23,3344 43545 DLOAD RVQ
052421,000117: 23,3345 00025 THETA # X = ARCSIN(SIN) (-45,45)
052422,000118:
052423,000119: 23,3346 75345 TRIG2 DLOAD SIGN # (135,-135)
052424,000120: 23,3347 06522 HIDPHALF
052425,000121: 23,3350 00023 SINTH
052426,000122: 23,3351 77625 DSU
052427,000123: 23,3352 00025 THETA
052428,000124: 23,3353 00025 STORE THETA # X = .5 WITH SIGN(SIN) - ARCSIN(SIN)
052429,000125: 23,3354 77616 RVQ # (+) - (+) OR (-) - (-)
052430,000126:
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Page 1244 |
052432,000128: # SMNB, NBSM, AND AXISROT, WHICH USED TO APPEAR HERE, HAVE BEEN
052433,000129: # COMBINED IN A ROUTINE CALLED AX*SR*T, WHICH APPEARS AMONG THE POWERED
052434,000130: # FLIGHT SUBROUTINES.
052435,000131:
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Page 1245 |
052437,000133: # CALCGA COMPUTES THE CDU DRIVING ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
052438,000134:
052439,000135: # THE INPUTS ARE 1) THE NAVIGATION BASE COORDINATES REFERRED TO ANY COORDINATE SYSTEM. THE THREE HALF-UNIT
052440,000136: # VECTORS ARE STORED AT XNB, YNB, AND ZNB. 2) THE DESIRED STABLE MEMBER COORDINATES REFERRED TO THE SAME
052441,000137: # COORDINATE SYSTEM ARE STORED AT XSM, YSM, AND ZSM.
052442,000138:
052443,000139: # THE OUTPUTS ARE THE THREE CDU DRIVING ANGLES AND ARE STORED SP AT THETAD, THETAD +1, AND THETAD +2.
052444,000140:
052445,000141: 23,3355 77601 CALCGA SETPD # PUSHDOWN 00-05, 16D-21D, 34D-37D
052446,000142: 23,3356 00001 0
052447,000143: 23,3357 47375 VLOAD VXV
052448,000144: 23,3360 02665 XNB # XNB = OGA (OUTER GIMBAL AXIS)
052449,000145: 23,3361 02651 YSM # YSM = IGA (INNER GIMBAL AXIS)
052450,000146: 23,3362 41456 UNIT PUSH # PD0 = UNIT(OGA X IGA) = MGA
052451,000147:
052452,000148: 23,3363 44041 DOT ITA
052453,000149: 23,3364 02701 ZNB
052454,000150: 23,3365 00051 S2
052455,000151: 23,3366 24021 STOVL COSTH # COS(OG) = MGA . ZNB
052456,000152: 23,3367 00001 0
052457,000153: 23,3370 77641 DOT
052458,000154: 23,3371 02673 YNB
052459,000155: 23,3372 34023 STCALL SINTH # SIN(OG) = MGA . YNB
052460,000156: 23,3373 47322 ARCTRIG
052461,000157: 23,3374 26740 STOVL OGC
052462,000158: 23,3375 00001 0
052463,000159:
052464,000160: 23,3376 50235 VXV DOT # PROVISION FOR MG ANGLE OF 90 DEGREES
052465,000161: 23,3377 02665 XNB
052466,000162: 23,3400 02651 YSM
052467,000163: 23,3401 77752 SL1
052468,000164: 23,3402 24021 STOVL COSTH # COS(MG) = IGA . (MGA X OGA)
052469,000165: 23,3403 02651 YSM
052470,000166: 23,3404 77641 DOT
052471,000167: 23,3405 02665 XNB
052472,000168: 23,3406 34023 STCALL SINTH # SIN(MG) = IGA . OGA
052473,000169: 23,3407 47322 ARCTRIG
052474,000170: 23,3410 02744 STORE MGC
052475,000171:
052476,000172: 23,3411 45246 ABS DSU
052477,000173: 23,3412 07540 .166...
052478,000174: 23,3413 77644 BPL
052479,000175: 23,3414 47433 GIMLOCK1 # IF ANGLE GREATER THAN 60 DEGREES
052480,000176:
052481,000177: 23,3415 50375 CALCGA1 VLOAD DOT
052482,000178: 23,3416 02657 ZSM
052483,000179: 23,3417 00001 0
052484,000180: 23,3420 24021 STOVL COSTH # COS(IG) = ZSM . MGA
052485,000181: 23,3421 02643 XSM
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Page 1246 |
052487,000183: 23,3422 45441 DOT STADR
052488,000184: 23,3423 43754 STCALL SINTH # SIN(IG) = XSM . MGA
052489,000185: 23,3424 47322 ARCTRIG
052490,000186:
052491,000187: 23,3425 26742 STOVL IGC
052492,000188: 23,3426 02740 OGC
052493,000189: 23,3427 77634 RTB
052494,000190: 23,3430 21621 V1STO2S
052495,000191: 23,3431 34322 STCALL THETAD
052496,000192: 23,3432 00051 S2
052497,000193:
052498,000194: 23,3433 77776 GIMLOCK1 EXIT
052499,000195: 23,3434 05567 TC ALARM
052500,000196: 23,3435 00401 OCT 00401
052501,000197: 23,3436 05504 TC UPFLAG # GIMBAL LOCK HAS OCCURED
052502,000198: 23,3437 00056 ADRES GLOKFAIL
052503,000199:
052504,000200: 23,3440 06042 TC INTPRET
052505,000201: 23,3441 77650 GOTO
052506,000202: 23,3442 47415 CALCGA1
052507,000203:
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Page 1247 |
052509,000205: # AXISGEN COMPUTES THE COORDINATES OF ONE COORDINATE SYSTEM REFERRED TO ANOTHER COORDINATE SYSTEM.
052510,000206:
052511,000207: # THE INPUTS ARE 1) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM A STORED AT STARAD. 2) THE STAR2 VECTOR
052512,000208: # REFERRED TO COORDINATE SYSTEM A STORED AT STARAD +6. 3) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM B STORED
052513,000209: # AT LOCATION 6 OF THE VAC AREA. 4) THE STAR2 VECTOR REFERRED TO COORDINATE SYSTEM B STORED AT LOCATION 12D OF
052514,000210: # THE VAC AREA.
052515,000211:
052516,000212: # THE OUTPUT DEFINES COORDINATE SYSTEM A REFERRED TO COORDINATE SYSTEM B. THE THREE HALF-UNIT VECTORS ARE STORED
052517,000213: # AT LOCATIONS XDC, XDC +6, XDC +12D, AND STARAD, STARAD +6, STARAD +12D.
052518,000214:
052519,000215: 23,3443 66370 AXISGEN AXT,1 SSP # PUSHDOWN 00-30D, 34D-37D
052520,000216: 23,3444 02714 STARAD +6
052521,000217: 23,3445 00051 S1
052522,000218: 23,3446 02700 STARAD -6
052523,000219:
052524,000220: 23,3447 77601 SETPD
052525,000221: 23,3450 00001 0
052526,000222: 23,3451 46773 AXISGEN1 VLOAD* VXV* # 06D UA = S1
052527,000223: 23,3452 02723 STARAD +12D,1 # STARAD +00D UB = S1
052528,000224: 23,3453 02731 STARAD +18D,1
052529,000225: 23,3454 77656 UNIT # 12D VA = UNIT(S1 X S2)
052530,000226: 23,3455 06731 STORE STARAD +18D,1 # STARAD +06D VB = UNIT(S1 X S2)
052531,000227: 23,3456 77773 VLOAD*
052532,000228: 23,3457 02723 STARAD +12D,1
052533,000229:
052534,000230: 23,3460 76433 VXV* VSL1
052535,000231: 23,3461 02731 STARAD +18D,1 # 18D WA = UA X VA
052536,000232: 23,3462 06737 STORE STARAD +24D,1 # STARAD +12D WB = UB X VB
052537,000233:
052538,000234: 23,3463 77700 TIX,1
052539,000235: 23,3464 47451 AXISGEN1
052540,000236:
052541,000237: 23,3465 66160 AXC,1 SXA,1
052542,000238: 23,3466 00006 6
052543,000239: 23,3467 00036 30D
052544,000240:
052545,000241: 23,3470 66370 AXT,1 SSP
052546,000242: 23,3471 00022 18D
052547,000243: 23,3472 00051 S1
052548,000244: 23,3473 00006 6
052549,000245:
052550,000246: 23,3474 66374 AXT,2 SSP
052551,000247: 23,3475 00006 6
052552,000248: 23,3476 00052 S2
052553,000249: 23,3477 00002 2
052554,000250:
052555,000251: 23,3500 76720 AXISGEN2 XCHX,1 VLOAD*
052556,000252: 23,3501 00036 30D # X1=-6 X2=+6 X1=-6 X2=+4 X1=-6 X2=+2
052557,000253: 23,3502 00001 0,1
052558,000254:
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Page 1248 |
052560,000256: 23,3503 62757 VXSC* PDVL* # J=(UA)(UB1) J=(UA)(UB2) J=(UA)(UB3)
052561,000257: 23,3504 75062 STARAD +6,2
052562,000258: 23,3505 00007 6,1
052563,000259: 23,3506 77757 VXSC*
052564,000260: 23,3507 75054 STARAD +12D,2
052565,000261: 23,3510 30031 STOVL* 24D # K=(VA)(VB1) J=(VA)(VB2) J=(VA)(VB3)
052566,000262: 23,3511 00015 12D,1
052567,000263:
052568,000264: 23,3512 53357 VXSC* VAD
052569,000265: 23,3513 75046 STARAD +18D,2 # L=(WA)(WB1) J=(WA)(WB2) J=(WA)(WB3)
052570,000266: 23,3514 76455 VAD VSL1
052571,000267: 23,3515 00031 24D
052572,000268: 23,3516 53520 XCHX,1 UNIT
052573,000269: 23,3517 00036 30D
052574,000270: 23,3520 06707 STORE XDC +18D,1 # XDC = L+J+K YDC = L+J+K ZDC = L+J+K
052575,000271:
052576,000272: 23,3521 77700 TIX,1
052577,000273: 23,3522 47523 AXISGEN3
052578,000274:
052579,000275: 23,3523 77704 AXISGEN3 TIX,2
052580,000276: 23,3524 47500 AXISGEN2
052581,000277:
052582,000278: 23,3525 77775 VLOAD
052583,000279: 23,3526 02665 XDC
052584,000280: 23,3527 26707 STOVL STARAD
052585,000281: 23,3530 02673 YDC
052586,000282: 23,3531 26715 STOVL STARAD +6
052587,000283: 23,3532 02701 ZDC
052588,000284: 23,3533 02723 STORE STARAD +12D
052589,000285:
052590,000286: 23,3534 77616 RVQ
052591,000287:
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Page 1249 |
052593,000289: 23,3535 05520 26075 QTSN45 2DEC .1768
052594,000290: 23,3537 05252 25253 .166... 2DEC .1666666667
052595,000291:
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Page 1250 There is no source code on this page of the original assembly listing. |
End of include-file INFLIGHT_ALIGNMENT_ROUTINES.agc. Parent file is MAIN.agc