Source Code
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These source-code files are part of a reconstructed copy of LM131 revision 1,
the final release of the Apollo 13 Lunar Module (LM) Apollo Guidance Computer
(AGC) software.
The source reconstruction began with source code of Luminary 131 previously
transcribed from a digitized copy of that program. A dump of the flight spare
core rope memory module B5, part number 2010802-171, serial number RAY 411,
was obtained. This module is the only module different between Luminary 131
and LM131 revision 1. The dump was disassembled and all changes were incorporated
into these source files. Note that page numbers in the reconstructed code match
those on the Luminary 131 printout, although the changed code would likely have
changed page numbers for a real LM131 revision 1 listing.
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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052181,000002: ## Copyright: Public domain.
052182,000003: ## Filename: INFLIGHT_ALIGNMENT_ROUTINES.agc
052183,000004: ## Purpose: A section of LM131 revision 1.
052184,000005: ## It is part of the reconstructed source code for the final
052185,000006: ## release of the flight software for the Lunar Module's (LM)
052186,000007: ## Apollo Guidance Computer (AGC) for Apollo 13. The code has
052187,000008: ## been reconstructed from a listing of Luminary 131 and a dump
052188,000009: ## of a core rope memory module B5, part number 2010802-171,
052189,000010: ## which is the only module different between LM131 revision 1
052190,000011: ## and Luminary 131. The executable generated from this source
052191,000012: ## has been verified against the module dump, so while the names,
052192,000013: ## comments, and ordering may not be exactly correct, the
052193,000014: ## resulting binary is.
052194,000015: ## Reference: pp. 1241-1250
052195,000016: ## Assembler: yaYUL
052196,000017: ## Contact: Ron Burkey <info@sandroid.org>.
052197,000018: ## Website: www.ibiblio.org/apollo/index.html
052198,000019: ## Mod history: 2022-10-28 MAS Created from Luminary 131.
052199,000020:
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Page 1241
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052201,000022: 22,3773 BANK 22
052202,000023: 23,2000 SETLOC INFLIGHT
052203,000024: 23,2000 BANK
052204,000025:
052205,000026: 23,3251 E5,1642 EBANK= XSM
052206,000027:
052207,000028: # CALCGTA COMPUTES THE GYRO TORQUE ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
052208,000029:
052209,000030: # THE INPUT IS THE DESIRED STABLE MEMBER COORDINATES REFERRED TO PRESENT STABLE MEMBER COORDINATES. THE THREE
052210,000031: # HALF-UNIT VECTORS ARE STORED AT XDC, YDC, AND ZDC.
052211,000032:
052212,000033: # THE OUTPUTS ARE THE THREE GYRO TORQUING ANGLES TO BE APPLIED TO THE Y, Z, AND X GYROS AND ARE STORED DP AT IGC,
052213,000034: # MGC, AND OGC RESPECTIVELY.
052214,000035:
052215,000036: 23,3251 COUNT* $$/INFLT
052216,000037: 23,3251 71220 CALCGTA ITA DLOAD # PUSHDOWN 00-03, 16D-27D, 34D-37D
052217,000038: 23,3252 00051 S2 # XDC = (XD1 XD2 XD3)
052218,000039: 23,3253 02665 XDC # YDC = (YD1 YD2 YD3)
052219,000040: 23,3254 65325 PDDL PDDL # ZDC = (ZD1 ZD2 ZD3)
052220,000041: 23,3255 06524 HI6ZEROS
052221,000042: 23,3256 02671 XDC +4
052222,000043: 23,3257 55476 DCOMP VDEF
052223,000044: 23,3260 77656 UNIT
052224,000045: 23,3261 14027 STODL ZPRIME # ZP = UNIT(-XD3 0 XD1) = (ZP1 ZP2 ZP3)
052225,000046: 23,3262 00027 ZPRIME
052226,000047:
052227,000048: 23,3263 77742 SR1
052228,000049: 23,3264 14023 STODL SINTH # SIN(IGC) = ZP1
052229,000050: 23,3265 00033 ZPRIME +4
052230,000051: 23,3266 77742 SR1
052231,000052: 23,3267 34021 STCALL COSTH # COS(IGC) = ZP3
052232,000053: 23,3270 47322 ARCTRIG
052233,000054:
052234,000055: 23,3271 16742 STODL IGC # Y GYRO TORQUING ANGLE FRACTION OF REV.
052235,000056: 23,3272 02667 XDC +2
052236,000057: 23,3273 77742 SR1
052237,000058: 23,3274 14023 STODL SINTH # SIN(MGC) = XD2
052238,000059: 23,3275 00027 ZPRIME
052239,000060:
052240,000061: 23,3276 65205 DMP PDDL
052241,000062: 23,3277 02671 XDC +4 # PD00 = (ZP1)(XD3)
052242,000063: 23,3300 00033 ZPRIME +4
052243,000064:
052244,000065: 23,3301 45205 DMP DSU
052245,000066: 23,3302 02665 XDC # MPAC = (ZP3)(XD1)
052246,000067: 23,3303 77626 STADR
052247,000068: 23,3304 43756 STCALL COSTH # COS(MGC) = MPAC - PD00
052248,000069: 23,3305 47322 ARCTRIG
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Page 1242
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052250,000071: 23,3306 26744 STOVL MGC # Z GYRO TORQUING ANGLE FRACTION OF REV.
052251,000072: 23,3307 00027 ZPRIME
052252,000073: 23,3310 77641 DOT
052253,000074: 23,3311 02701 ZDC
052254,000075: 23,3312 24021 STOVL COSTH # COS(OGC) = ZP . ZDC
052255,000076: 23,3313 00027 ZPRIME
052256,000077: 23,3314 77641 DOT
052257,000078: 23,3315 02673 YDC
052258,000079: 23,3316 34023 STCALL SINTH # SIN(OGC) = ZP . YDC
052259,000080: 23,3317 47322 ARCTRIG
052260,000081:
052261,000082: 23,3320 36740 STCALL OGC # X GYRO TORQUING ANGLE FRACTION OF REV.
052262,000083: 23,3321 00051 S2
052263,000084:
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Page 1243
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052265,000086: # ARCTRIG COMPUTES AN ANGLE GIVEN THE SINE AND COSINE OF THIS ANGLE.
052266,000087:
052267,000088: # THE INPUTS ARE SIN/4 AND COS/4 STORED DP AT SINTH AND COSTH.
052268,000089:
052269,000090: # THE OUTPUT IS THE CALCULATED ANGLE BETWEEN +.5 AND -.5 REVOLUTIONS AND STORED AT THETA. THE OUTPUT IS ALSO
052270,000091: # AVAILABLE AT MPAC.
052271,000092:
052272,000093: 23,3322 51545 ARCTRIG DLOAD ABS # PUSHDOWN 16D-21D
052273,000094: 23,3323 00023 SINTH
052274,000095: 23,3324 50025 DSU BMN
052275,000096: 23,3325 07536 QTSN45 # ABS(SIN/4) - SIN(45)/4
052276,000097: 23,3326 47335 TRIG1 # IF (-45,45) OR (135,-135)
052277,000098:
052278,000099: 23,3327 72545 DLOAD SL1 # (45,135) OR (-135,-45)
052279,000100: 23,3330 00021 COSTH
052280,000101: 23,3331 75326 ACOS SIGN
052281,000102: 23,3332 00023 SINTH
052282,000103: 23,3333 00025 STORE THETA # X = ARCCOS(COS) WITH SIGN(SIN)
052283,000104: 23,3334 77616 RVQ
052284,000105:
052285,000106: 23,3335 72545 TRIG1 DLOAD SL1 # (-45,45) OR (135,-135)
052286,000107: 23,3336 00023 SINTH
052287,000108: 23,3337 77736 ASIN
052288,000109: 23,3340 14025 STODL THETA # X = ARCSIN(SIN) WITH SIGN(SIN)
052289,000110: 23,3341 00021 COSTH
052290,000111: 23,3342 77640 BMN
052291,000112: 23,3343 47346 TRIG2 # IF (135,-135)
052292,000113:
052293,000114: 23,3344 43545 DLOAD RVQ
052294,000115: 23,3345 00025 THETA # X = ARCSIN(SIN) (-45,45)
052295,000116:
052296,000117: 23,3346 75345 TRIG2 DLOAD SIGN # (135,-135)
052297,000118: 23,3347 06522 HIDPHALF
052298,000119: 23,3350 00023 SINTH
052299,000120: 23,3351 77625 DSU
052300,000121: 23,3352 00025 THETA
052301,000122: 23,3353 00025 STORE THETA # X = .5 WITH SIGN(SIN) - ARCSIN(SIN)
052302,000123: 23,3354 77616 RVQ # (+) - (+) OR (-) - (-)
052303,000124:
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Page 1244
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052305,000126: # SMNB, NBSM, AND AXISROT, WHICH USED TO APPEAR HERE, HAVE BEEN
052306,000127: # COMBINED IN A ROUTINE CALLED AX*SR*T, WHICH APPEARS AMONG THE POWERED
052307,000128: # FLIGHT SUBROUTINES.
052308,000129:
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Page 1245
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052310,000131: # CALCGA COMPUTES THE CDU DRIVING ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
052311,000132:
052312,000133: # THE INPUTS ARE 1) THE NAVIGATION BASE COORDINATES REFERRED TO ANY COORDINATE SYSTEM. THE THREE HALF-UNIT
052313,000134: # VECTORS ARE STORED AT XNB, YNB, AND ZNB. 2) THE DESIRED STABLE MEMBER COORDINATES REFERRED TO THE SAME
052314,000135: # COORDINATE SYSTEM ARE STORED AT XSM, YSM, AND ZSM.
052315,000136:
052316,000137: # THE OUTPUTS ARE THE THREE CDU DRIVING ANGLES AND ARE STORED SP AT THETAD, THETAD +1, AND THETAD +2.
052317,000138:
052318,000139: 23,3355 77601 CALCGA SETPD # PUSHDOWN 00-05, 16D-21D, 34D-37D
052319,000140: 23,3356 00001 0
052320,000141: 23,3357 47375 VLOAD VXV
052321,000142: 23,3360 02665 XNB # XNB = OGA (OUTER GIMBAL AXIS)
052322,000143: 23,3361 02651 YSM # YSM = IGA (INNER GIMBAL AXIS)
052323,000144: 23,3362 41456 UNIT PUSH # PD0 = UNIT(OGA X IGA) = MGA
052324,000145:
052325,000146: 23,3363 44041 DOT ITA
052326,000147: 23,3364 02701 ZNB
052327,000148: 23,3365 00051 S2
052328,000149: 23,3366 24021 STOVL COSTH # COS(OG) = MGA . ZNB
052329,000150: 23,3367 00001 0
052330,000151: 23,3370 77641 DOT
052331,000152: 23,3371 02673 YNB
052332,000153: 23,3372 34023 STCALL SINTH # SIN(OG) = MGA . YNB
052333,000154: 23,3373 47322 ARCTRIG
052334,000155: 23,3374 26740 STOVL OGC
052335,000156: 23,3375 00001 0
052336,000157:
052337,000158: 23,3376 50235 VXV DOT # PROVISION FOR MG ANGLE OF 90 DEGREES
052338,000159: 23,3377 02665 XNB
052339,000160: 23,3400 02651 YSM
052340,000161: 23,3401 77752 SL1
052341,000162: 23,3402 24021 STOVL COSTH # COS(MG) = IGA . (MGA X OGA)
052342,000163: 23,3403 02651 YSM
052343,000164: 23,3404 77641 DOT
052344,000165: 23,3405 02665 XNB
052345,000166: 23,3406 34023 STCALL SINTH # SIN(MG) = IGA . OGA
052346,000167: 23,3407 47322 ARCTRIG
052347,000168: 23,3410 02744 STORE MGC
052348,000169:
052349,000170: 23,3411 45246 ABS DSU
052350,000171: 23,3412 07540 .166...
052351,000172: 23,3413 77644 BPL
052352,000173: 23,3414 47433 GIMLOCK1 # IF ANGLE GREATER THAN 60 DEGREES
052353,000174:
052354,000175: 23,3415 50375 CALCGA1 VLOAD DOT
052355,000176: 23,3416 02657 ZSM
052356,000177: 23,3417 00001 0
052357,000178: 23,3420 24021 STOVL COSTH # COS(IG) = ZSM . MGA
052358,000179: 23,3421 02643 XSM
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Page 1246
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052360,000181: 23,3422 45441 DOT STADR
052361,000182: 23,3423 43754 STCALL SINTH # SIN(IG) = XSM . MGA
052362,000183: 23,3424 47322 ARCTRIG
052363,000184:
052364,000185: 23,3425 26742 STOVL IGC
052365,000186: 23,3426 02740 OGC
052366,000187: 23,3427 77634 RTB
052367,000188: 23,3430 21621 V1STO2S
052368,000189: 23,3431 34322 STCALL THETAD
052369,000190: 23,3432 00051 S2
052370,000191:
052371,000192: 23,3433 77776 GIMLOCK1 EXIT
052372,000193: 23,3434 05567 TC ALARM
052373,000194: 23,3435 00401 OCT 00401
052374,000195: 23,3436 05504 TC UPFLAG # GIMBAL LOCK HAS OCCURED
052375,000196: 23,3437 00056 ADRES GLOKFAIL
052376,000197:
052377,000198: 23,3440 06042 TC INTPRET
052378,000199: 23,3441 77650 GOTO
052379,000200: 23,3442 47415 CALCGA1
052380,000201:
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Page 1247
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052382,000203: # AXISGEN COMPUTES THE COORDINATES OF ONE COORDINATE SYSTEM REFERRED TO ANOTHER COORDINATE SYSTEM.
052383,000204:
052384,000205: # THE INPUTS ARE 1) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM A STORED AT STARAD. 2) THE STAR2 VECTOR
052385,000206: # REFERRED TO COORDINATE SYSTEM A STORED AT STARAD +6. 3) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM B STORED
052386,000207: # AT LOCATION 6 OF THE VAC AREA. 4) THE STAR2 VECTOR REFERRED TO COORDINATE SYSTEM B STORED AT LOCATION 12D OF
052387,000208: # THE VAC AREA.
052388,000209:
052389,000210: # THE OUTPUT DEFINES COORDINATE SYSTEM A REFERRED TO COORDINATE SYSTEM B. THE THREE HALF-UNIT VECTORS ARE STORED
052390,000211: # AT LOCATIONS XDC, XDC +6, XDC +12D, AND STARAD, STARAD +6, STARAD +12D.
052391,000212:
052392,000213: 23,3443 66370 AXISGEN AXT,1 SSP # PUSHDOWN 00-30D, 34D-37D
052393,000214: 23,3444 02714 STARAD +6
052394,000215: 23,3445 00051 S1
052395,000216: 23,3446 02700 STARAD -6
052396,000217:
052397,000218: 23,3447 77601 SETPD
052398,000219: 23,3450 00001 0
052399,000220: 23,3451 46773 AXISGEN1 VLOAD* VXV* # 06D UA = S1
052400,000221: 23,3452 02723 STARAD +12D,1 # STARAD +00D UB = S1
052401,000222: 23,3453 02731 STARAD +18D,1
052402,000223: 23,3454 77656 UNIT # 12D VA = UNIT(S1 X S2)
052403,000224: 23,3455 06731 STORE STARAD +18D,1 # STARAD +06D VB = UNIT(S1 X S2)
052404,000225: 23,3456 77773 VLOAD*
052405,000226: 23,3457 02723 STARAD +12D,1
052406,000227:
052407,000228: 23,3460 76433 VXV* VSL1
052408,000229: 23,3461 02731 STARAD +18D,1 # 18D WA = UA X VA
052409,000230: 23,3462 06737 STORE STARAD +24D,1 # STARAD +12D WB = UB X VB
052410,000231:
052411,000232: 23,3463 77700 TIX,1
052412,000233: 23,3464 47451 AXISGEN1
052413,000234:
052414,000235: 23,3465 66160 AXC,1 SXA,1
052415,000236: 23,3466 00006 6
052416,000237: 23,3467 00036 30D
052417,000238:
052418,000239: 23,3470 66370 AXT,1 SSP
052419,000240: 23,3471 00022 18D
052420,000241: 23,3472 00051 S1
052421,000242: 23,3473 00006 6
052422,000243:
052423,000244: 23,3474 66374 AXT,2 SSP
052424,000245: 23,3475 00006 6
052425,000246: 23,3476 00052 S2
052426,000247: 23,3477 00002 2
052427,000248:
052428,000249: 23,3500 76720 AXISGEN2 XCHX,1 VLOAD*
052429,000250: 23,3501 00036 30D # X1=-6 X2=+6 X1=-6 X2=+4 X1=-6 X2=+2
052430,000251: 23,3502 00001 0,1
052431,000252:
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Page 1248
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052433,000254: 23,3503 62757 VXSC* PDVL* # J=(UA)(UB1) J=(UA)(UB2) J=(UA)(UB3)
052434,000255: 23,3504 75062 STARAD +6,2
052435,000256: 23,3505 00007 6,1
052436,000257: 23,3506 77757 VXSC*
052437,000258: 23,3507 75054 STARAD +12D,2
052438,000259: 23,3510 30031 STOVL* 24D # K=(VA)(VB1) J=(VA)(VB2) J=(VA)(VB3)
052439,000260: 23,3511 00015 12D,1
052440,000261:
052441,000262: 23,3512 53357 VXSC* VAD
052442,000263: 23,3513 75046 STARAD +18D,2 # L=(WA)(WB1) J=(WA)(WB2) J=(WA)(WB3)
052443,000264: 23,3514 76455 VAD VSL1
052444,000265: 23,3515 00031 24D
052445,000266: 23,3516 53520 XCHX,1 UNIT
052446,000267: 23,3517 00036 30D
052447,000268: 23,3520 06707 STORE XDC +18D,1 # XDC = L+J+K YDC = L+J+K ZDC = L+J+K
052448,000269:
052449,000270: 23,3521 77700 TIX,1
052450,000271: 23,3522 47523 AXISGEN3
052451,000272:
052452,000273: 23,3523 77704 AXISGEN3 TIX,2
052453,000274: 23,3524 47500 AXISGEN2
052454,000275:
052455,000276: 23,3525 77775 VLOAD
052456,000277: 23,3526 02665 XDC
052457,000278: 23,3527 26707 STOVL STARAD
052458,000279: 23,3530 02673 YDC
052459,000280: 23,3531 26715 STOVL STARAD +6
052460,000281: 23,3532 02701 ZDC
052461,000282: 23,3533 02723 STORE STARAD +12D
052462,000283:
052463,000284: 23,3534 77616 RVQ
052464,000285:
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Page 1249
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052466,000287: 23,3535 05520 26075 QTSN45 2DEC .1768
052467,000288: 23,3537 05252 25253 .166... 2DEC .1666666667
052468,000289:
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Page 1250
There is no source code on this page of the original assembly listing.
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End of include-file INFLIGHT_ALIGNMENT_ROUTINES.agc. Parent file is MAIN.agc