Source Code
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These source-code files are part of a reconstructed copy of Comanche 44, the
initial release (though not the final mission release) of the Apollo 10
Command Module (CM) Apollo Guidance Computer (AGC) software. Subsequent releases
were Comanche 45 and Comanche 45/2 (the flown release on Apollo 10). The reconstruction
is believed to be exactly accurate, but in the absence of an actual Apollo-era
listing of Comanche 44, some explanation of the reconstruction process is needed
to insure confidence in that accuracy.
The starting point was the source code of Comanche 51
(separately previously reconstructed from an Apollo-era listing of Comanche 55,
flown on Apollo 11). Comanche 51 source code was then modified
by undoing changes known to have been made between revisions 44 and 51. The now-reconstructed
Comanche 44 source code was verified by assembling it and checking that the assembled code had
the expected known-correct memory-bank checksums.
Note that page numbers in the reconstructed code match those on the Comanche 55 printout,
although the source code would likely have different page numbers in a contemporary
Comanche 44 listing.
Annotations that were not present in the contemporary source code have been added to the reconstructed
code to justify each change relative to Comanche 51. Here's a guide to the Apollo documentation referenced
in those annotations:
In most cases, only the titles (rather than the full texts) of PCRs are known. In addition to the
explanatory annotations, there is also
a step-by-step commentary about the reconstruction process.
Comments expected to have been present in 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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058185,000002: ## Copyright: Public domain.
058186,000003: ## Filename: INFLIGHT_ALIGNMENT_ROUTINES.agc
058187,000004: ## Purpose: A section of Comanche revision 044.
058188,000005: ## It is part of the reconstructed source code for the
058189,000006: ## original release of the flight software for the Command
058190,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 10.
058191,000008: ## The code has been recreated from a copy of Comanche 055. It
058192,000009: ## has been adapted such that the resulting bugger words
058193,000010: ## exactly match those specified for Comanche 44 in NASA drawing
058194,000011: ## 2021153D, which gives relatively high confidence that the
058195,000012: ## reconstruction is correct.
058196,000013: ## Assembler: yaYUL
058197,000014: ## Contact: Ron Burkey <info@sandroid.org>.
058198,000015: ## Website: www.ibiblio.org/apollo/index.html
058199,000016: ## Mod history: 2020-12-03 MAS Created from Comanche 51.
058200,000017:
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Page 1355
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058202,000019: 22,3510 BANK 22
058203,000020: 23,2000 SETLOC INFLIGHT
058204,000021: 23,2000 BANK
058205,000022:
058206,000023: 23,3205 E5,1671 EBANK= XSM
058207,000024:
058208,000025: # CALCGTA COMPUTES THE GYRO TORQUE ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
058209,000026:
058210,000027: # THE INPUT IS THE DESIRED STABLE MEMBER COORDINATES REFERRED TO PRESENT STABLE MEMBER COORDINATES. THE THREE
058211,000028: # HALF-UNIT VECTORS ARE STORED AT XDC, YDC, AND ZDC.
058212,000029:
058213,000030: # THE OUTPUTS ARE THE THREE GYRO TORQUING ANGLES TO BE APPLIED TO THE Y, Z, AND X GYROS AND ARE STORED DP AT IGC,
058214,000031: # MGC, AND OGC RESPECTIVELY.
058215,000032:
058216,000033: 23,3205 COUNT 23/INFLT
058217,000034:
058218,000035: 23,3205 71220 CALCGTA ITA DLOAD # PUSHDOWN 00-03, 16D-27D, 34D-37D
058219,000036: 23,3206 00051 S2 # XDC = (XD1 XD2 XD3)
058220,000037: 23,3207 02714 XDC # YDC = (YD1 YD2 YD3)
058221,000038: 23,3210 65325 PDDL PDDL # ZDC = (ZD1 ZD2 ZD3)
058222,000039: 23,3211 15335 HI6ZEROS
058223,000040: 23,3212 02720 XDC +4
058224,000041: 23,3213 55476 DCOMP VDEF
058225,000042: 23,3214 77656 UNIT
058226,000043: 23,3215 14027 STODL ZPRIME # ZP = UNIT(-XD3 0 XD1) = (ZP1 ZP2 ZP3)
058227,000044: 23,3216 00027 ZPRIME
058228,000045:
058229,000046: 23,3217 77742 SR1
058230,000047: 23,3220 14023 STODL SINTH # SIN(IGC) = ZP1
058231,000048: 23,3221 00033 ZPRIME +4
058232,000049: 23,3222 77742 SR1
058233,000050: 23,3223 34021 STCALL COSTH # COS(IGC) = ZP3
058234,000051: 23,3224 47256 ARCTRIG
058235,000052:
058236,000053: 23,3225 16762 STODL IGC # Y GYRO TORQUING ANGLE FRACTION OF REV.
058237,000054: 23,3226 02716 XDC +2
058238,000055: 23,3227 77742 SR1
058239,000056: 23,3230 14023 STODL SINTH # SIN(MGC) = XD2
058240,000057: 23,3231 00027 ZPRIME
058241,000058:
058242,000059: 23,3232 65205 DMP PDDL
058243,000060: 23,3233 02720 XDC +4 # PD00 = (ZP1)(XD3)
058244,000061: 23,3234 00033 ZPRIME +4
058245,000062:
058246,000063: 23,3235 45205 DMP DSU
058247,000064: 23,3236 02714 XDC # MPAC = (ZP3)(XD1)
058248,000065: 23,3237 77626 STADR
058249,000066: 23,3240 43756 STCALL COSTH # COS(MGC) = MPAC - PD00
058250,000067: 23,3241 47256 ARCTRIG
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Page 1356
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058252,000069: 23,3242 26764 STOVL MGC # Z GYRO TORQUING ANGLE FRACTION OF REV.
058253,000070: 23,3243 00027 ZPRIME
058254,000071: 23,3244 77641 DOT
058255,000072: 23,3245 02730 ZDC
058256,000073: 23,3246 24021 STOVL COSTH # COS(OGC) = ZP . ZDC
058257,000074: 23,3247 00027 ZPRIME
058258,000075: 23,3250 77641 DOT
058259,000076: 23,3251 02722 YDC
058260,000077: 23,3252 34023 STCALL SINTH # SIN(OGC) = ZP . YDC
058261,000078: 23,3253 47256 ARCTRIG
058262,000079:
058263,000080: 23,3254 36760 STCALL OGC # X GYRO TORQUING ANGLE FRACTION OF REV.
058264,000081: 23,3255 00051 S2
058265,000082:
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Page 1357
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058267,000084: # ARCTRIG COMPUTES AN ANGLE GIVEN THE SINE AND COSINE OF THIS ANGLE.
058268,000085:
058269,000086: # THE INPUTS ARE SIN/4 AND COS/4 STORED DP AT SINTH AND COSTH.
058270,000087:
058271,000088: # THE OUTPUT IS THE CALCULATED ANGLE BETWEEN +.5 AND -.5 REVOLUTIONS AND STORED AT THETA. THE OUTPUT IS ALSO
058272,000089: # AVAILABLE AT MPAC.
058273,000090:
058274,000091: 23,3256 51545 ARCTRIG DLOAD ABS # PUSHDOWN 16D-21D
058275,000092: 23,3257 00023 SINTH
058276,000093: 23,3260 50025 DSU BMN
058277,000094: 23,3261 07474 QTSN45 # ABS(SIN/4) - SIN(45)/4
058278,000095: 23,3262 47271 TRIG1 # IF (-45,45) OR (135,-135)
058279,000096:
058280,000097: 23,3263 72545 DLOAD SL1 # (45,135) OR (-135,-45)
058281,000098: 23,3264 00021 COSTH
058282,000099: 23,3265 75326 ACOS SIGN
058283,000100: 23,3266 00023 SINTH
058284,000101: 23,3267 00025 STORE THETA # X = ARCCOS(COS) WITH SIGN(SIN)
058285,000102: 23,3270 77616 RVQ
058286,000103:
058287,000104: 23,3271 72545 TRIG1 DLOAD SL1 # (-45,45) OR (135,-135)
058288,000105: 23,3272 00023 SINTH
058289,000106: 23,3273 77736 ASIN
058290,000107: 23,3274 14025 STODL THETA # X = ARCSIN(SIN) WITH SIGN(SIN)
058291,000108: 23,3275 00021 COSTH
058292,000109: 23,3276 77640 BMN
058293,000110: 23,3277 47302 TRIG2 # IF (135,-135)
058294,000111:
058295,000112: 23,3300 43545 DLOAD RVQ
058296,000113: 23,3301 00025 THETA # X = ARCSIN(SIN) (-45,45)
058297,000114:
058298,000115: 23,3302 75345 TRIG2 DLOAD SIGN # (135,-135)
058299,000116: 23,3303 15333 HIDPHALF
058300,000117: 23,3304 00023 SINTH
058301,000118: 23,3305 77625 DSU
058302,000119: 23,3306 00025 THETA
058303,000120: 23,3307 00025 STORE THETA # X = .5 WITH SIGN(SIN) - ARCSIN(SIN)
058304,000121: 23,3310 77616 RVQ # (+) - (+) OR (-) - (-)
058305,000122:
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Page 1358
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058307,000124: # SMNB, NBSM, AND AXISROT, WHICH USED TO APPEAR HERE, HAVE BEEN
058308,000125: # COMBINED IN A ROUTINE CALLED AX*SR*T, WHICH APPEARS AMONG THE POWERED
058309,000126: # FLIGHT SUBROUTINES.
058310,000127:
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Page 1359
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058312,000129: # CALCGA COMPUTES THE CDU DRIVING ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
058313,000130:
058314,000131: # THE INPUTS ARE 1) THE NAVIGATION BASE COORDINATES REFERRED TO ANY COORDINATE SYSTEM. THE THREE HALF-UNIT
058315,000132: # VECTORS ARE STORED AT XNB, YNB, AND ZNB. 2) THE DESIRED STABLE MEMBER COORDINATES REFERRED TO THE SAME
058316,000133: # COORDINATE SYSTEM ARE STORED AT XSM, YSM, AND ZSM.
058317,000134:
058318,000135: # THE OUTPUTS ARE THE THREE CDU DRIVING ANGLES AND ARE STORED SP AT THETAD, THETAD +1, AND THETAD +2.
058319,000136:
058320,000137: 23,3311 77601 CALCGA SETPD # PUSHDOWN 00-05, 16D-21D, 34D-37D
058321,000138: 23,3312 00001 0
058322,000139: 23,3313 47375 VLOAD VXV
058323,000140: 23,3314 02714 XNB # XNB = OGA (OUTER GIMBAL AXIS)
058324,000141: 23,3315 02700 YSM # YSM = IGA (INNER GIMBAL AXIS)
058325,000142: 23,3316 41456 UNIT PUSH # PD0 = UNIT(OGA X IGA) = MGA
058326,000143:
058327,000144: 23,3317 44041 DOT ITA
058328,000145: 23,3320 02730 ZNB
058329,000146: 23,3321 00051 S2
058330,000147: 23,3322 24021 STOVL COSTH # COS(OG) = MGA . ZNB
058331,000148: 23,3323 00001 0
058332,000149: 23,3324 77641 DOT
058333,000150: 23,3325 02722 YNB
058334,000151: 23,3326 34023 STCALL SINTH # SIN(OG) = MGA . YNB
058335,000152: 23,3327 47256 ARCTRIG
058336,000153: 23,3330 26760 STOVL OGC
058337,000154: 23,3331 00001 0
058338,000155:
058339,000156: 23,3332 50235 VXV DOT # PROVISION FOR MG ANGLE OF 90 DEGREES
058340,000157: 23,3333 02714 XNB
058341,000158: 23,3334 02700 YSM
058342,000159: 23,3335 77752 SL1
058343,000160: 23,3336 24021 STOVL COSTH # COS(MG) = IGA . (MGA X OGA)
058344,000161: 23,3337 02700 YSM
058345,000162: 23,3340 77641 DOT
058346,000163: 23,3341 02714 XNB
058347,000164: 23,3342 34023 STCALL SINTH # SIN(MG) = IGA . OGA
058348,000165: 23,3343 47256 ARCTRIG
058349,000166: 23,3344 02764 STORE MGC
058350,000167:
058351,000168: 23,3345 45246 ABS DSU
058352,000169: 23,3346 07476 .166...
058353,000170: 23,3347 77644 BPL
058354,000171: 23,3350 47371 GIMLOCK1 # IF ANGLE GREATER THAN 60 DEGREES
058355,000172:
058356,000173: 23,3351 50375 CALCGA1 VLOAD DOT
058357,000174: 23,3352 02706 ZSM
058358,000175: 23,3353 00001 0
058359,000176: 23,3354 24021 STOVL COSTH # COS(IG) = ZSM . MGA
058360,000177: 23,3355 02672 XSM
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Page 1360
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058362,000179: 23,3356 45441 DOT STADR
058363,000180: 23,3357 43754 STCALL SINTH # SIN(IG) = XSM . MGA
058364,000181: 23,3360 47256 ARCTRIG
058365,000182:
058366,000183: 23,3361 26762 STOVL IGC
058367,000184: 23,3362 02760 OGC
058368,000185: 23,3363 43034 RTB BONCLR
058369,000186: 23,3364 45552 V1STO2S
058370,000187: 23,3365 00200 CPHIFLAG
058371,000188: 23,3366 00051 S2
058372,000189: 23,3367 35156 STCALL THETAD
058373,000190: 23,3370 00051 S2
058374,000191:
058375,000192: 23,3371 77776 GIMLOCK1 EXIT
058376,000193: 23,3372 05650 TC ALARM
058377,000194: 23,3373 00401 OCT 00401
058378,000195: 23,3374 05546 TC UPFLAG # GIMBAL LOCK HAS OCCURED
058379,000196: 23,3375 00056 ADRES GLOKFAIL
058380,000197:
058381,000198: 23,3376 06006 TC INTPRET
058382,000199: 23,3377 77650 GOTO
058383,000200: 23,3400 47351 CALCGA1
058384,000201:
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Page 1361
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058386,000203: # AXISGEN COMPUTES THE COORDINATES OF ONE COORDINATE SYSTEM REFERRED TO ANOTHER COORDINATE SYSTEM.
058387,000204:
058388,000205: # THE INPUTS ARE 1) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM A STORED AT STARAD. 2) THE STAR2 VECTOR
058389,000206: # REFERRED TO COORDINATE SYSTEM A STORED AT STARAD +6. 3) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM B STORED
058390,000207: # AT LOCATION 6 OF THE VAC AREA. 4) THE STAR2 VECTOR REFERRED TO COORDINATE SYSTEM B STORED AT LOCATION 12D OF
058391,000208: # THE VAC AREA.
058392,000209:
058393,000210: # THE OUTPUT DEFINES COORDINATE SYSTEM A REFERRED TO COORDINATE SYSTEM B. THE THREE HALF-UNIT VECTORS ARE STORED
058394,000211: # AT LOCATIONS XDC, XDC +6, XDC +12D, AND STARAD, STARAD +6, STARAD +12D.
058395,000212:
058396,000213: 23,3401 66370 AXISGEN AXT,1 SSP # PUSHDOWN 00-30D, 34D-37D
058397,000214: 23,3402 02743 STARAD +6
058398,000215: 23,3403 00051 S1
058399,000216: 23,3404 02727 STARAD -6
058400,000217:
058401,000218: 23,3405 77601 SETPD
058402,000219: 23,3406 00001 0
058403,000220: 23,3407 46773 AXISGEN1 VLOAD* VXV* # 06D UA = S1
058404,000221: 23,3410 02752 STARAD +12D,1 # STARAD +00D UB = S1
058405,000222: 23,3411 02760 STARAD +18D,1
058406,000223: 23,3412 77656 UNIT # 12D VA = UNIT(S1 X S2)
058407,000224: 23,3413 06760 STORE STARAD +18D,1 # STARAD +06D VB = UNIT(S1 X S2)
058408,000225: 23,3414 77773 VLOAD*
058409,000226: 23,3415 02752 STARAD +12D,1
058410,000227:
058411,000228: 23,3416 76433 VXV* VSL1
058412,000229: 23,3417 02760 STARAD +18D,1 # 18D WA = UA X VA
058413,000230: 23,3420 06766 STORE STARAD +24D,1 # STARAD +12D WB = UB X VB
058414,000231:
058415,000232: 23,3421 77700 TIX,1
058416,000233: 23,3422 47407 AXISGEN1
058417,000234:
058418,000235: 23,3423 66160 AXC,1 SXA,1
058419,000236: 23,3424 00006 6
058420,000237: 23,3425 00036 30D
058421,000238:
058422,000239: 23,3426 66370 AXT,1 SSP
058423,000240: 23,3427 00022 18D
058424,000241: 23,3430 00051 S1
058425,000242: 23,3431 00006 6
058426,000243:
058427,000244: 23,3432 66374 AXT,2 SSP
058428,000245: 23,3433 00006 6
058429,000246: 23,3434 00052 S2
058430,000247: 23,3435 00002 2
058431,000248:
058432,000249: 23,3436 76720 AXISGEN2 XCHX,1 VLOAD*
058433,000250: 23,3437 00036 30D # X1=-6 X2=+6 X1=-6 X2=+4 X1=-6 X2=+2
058434,000251: 23,3440 00001 0,1
058435,000252:
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Page 1362
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058437,000254: 23,3441 62757 VXSC* PDVL* # J=(UA)(UB1) J=(UA)(UB2) J=(UA)(UB3)
058438,000255: 23,3442 75033 STARAD +6,2
058439,000256: 23,3443 00007 6,1
058440,000257: 23,3444 77757 VXSC*
058441,000258: 23,3445 75025 STARAD +12D,2
058442,000259: 23,3446 30031 STOVL* 24D # K=(VA)(VB1) J=(VA)(VB2) J=(VA)(VB3)
058443,000260: 23,3447 00015 12D,1
058444,000261:
058445,000262: 23,3450 53357 VXSC* VAD
058446,000263: 23,3451 75017 STARAD +18D,2 # L=(WA)(WB1) J=(WA)(WB2) J=(WA)(WB3)
058447,000264: 23,3452 76455 VAD VSL1
058448,000265: 23,3453 00031 24D
058449,000266: 23,3454 53520 XCHX,1 UNIT
058450,000267: 23,3455 00036 30D
058451,000268: 23,3456 06736 STORE XDC +18D,1 # XDC = L+J+K YDC = L+J+K ZDC = L+J+K
058452,000269:
058453,000270: 23,3457 77700 TIX,1
058454,000271: 23,3460 47461 AXISGEN3
058455,000272:
058456,000273: 23,3461 77704 AXISGEN3 TIX,2
058457,000274: 23,3462 47436 AXISGEN2
058458,000275:
058459,000276: 23,3463 77775 VLOAD
058460,000277: 23,3464 02714 XDC
058461,000278: 23,3465 26736 STOVL STARAD
058462,000279: 23,3466 02722 YDC
058463,000280: 23,3467 26744 STOVL STARAD +6
058464,000281: 23,3470 02730 ZDC
058465,000282: 23,3471 02752 STORE STARAD +12D
058466,000283:
058467,000284: 23,3472 77616 RVQ
058468,000285:
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Page 1363
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058470,000287: 23,3473 05520 26075 QTSN45 2DEC .1768
058471,000288: 23,3475 05252 25253 .166... 2DEC .1666666667
058472,000289:
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Page 1364
This page is empty.
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058475,000292:
058476,000293:
058477,000294:
End of include-file INFLIGHT_ALIGNMENT_ROUTINES.agc. Parent file is MAIN.agc