Source Code
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These source-code files are part of a reconstructed copy of Comanche 51, the
initial release (though not the final mission release) of the Apollo 11
Command Module (CM) Apollo Guidance Computer (AGC) software. The flown, final
release was Comanche 55. The reconstruction is believed to be exactly accurate,
but in the absence of an actual Apollo-era listing of Comanche 51, some
explanation of the reconstruction process is needed to insure confidence in
that accuracy.
The starting point was the source code of Comanche 55, whose original source code
is available. Comanche 55 source code was then modified by undoing changes known
to have been made between revisions 51 and 55. The most-significant steps involved
reverting changes related to the R-2 lunar potential model, the details of which
were known from the previous, separate, independent reconstruction of the Apollo 10
Lunar Module software Luminary 69/2. The now-reconstructed
Comanche 51 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 or Luminary 69 printouts, although
the source code would likely have different page numbers in a contemporary Comanche 51 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 55. Here's a guide
to some of the Apollo documentation relevant to those annotations:
Among documentation not actually referenced in the annotations, there is
a short writeup about the reconstruction process in our software repository
that may be helpful in understanding it from a different perspective. There's also
a handy table
that lists what the number of memory-words should be for each routine in Comanche 51,
which could make a nice double-check; however, we've not performed that double-check ourselves.
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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045158,000002: ## Copyright: Public domain.
045159,000003: ## Filename: RCS-CSM_DAP_EXECUTIVE_PROGRAMS.agc
045160,000004: ## Purpose: A section of Comanche revision 051.
045161,000005: ## It is part of the reconstructed source code for the
045162,000006: ## original release of the flight software for the Command
045163,000007: ## Module's (CM) Apollo Guidance Computer (AGC) for Apollo 11.
045164,000008: ## The code has been recreated from a copy of Comanche 055. It
045165,000009: ## has been adapted such that the resulting bugger words
045166,000010: ## exactly match those specified for Comanche 51 in NASA drawing
045167,000011: ## 2021153D, which gives relatively high confidence that the
045168,000012: ## reconstruction is correct.
045169,000013: ## Reference: pp. 1037-1038
045170,000014: ## Assembler: yaYUL
045171,000015: ## Contact: Ron Burkey <info@sandroid.org>.
045172,000016: ## Website: www.ibiblio.org/apollo/index.html
045173,000017: ## Mod history: 2019-07-30 MAS Created from Comanche 55.
045174,000018:
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Page 1037
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045176,000020: # CALCULATION OF AMGB, AMBG ONCE EVERY SECOND
045177,000021:
045178,000022: # AMGB = 1 SIN(PSI) 0
045179,000023: # 0 COS(PSI)COS(PHI) SIN(PHI)
045180,000024: # 0 -COS(PSI)SIN(PHI) COS(PHI)
045181,000025:
045182,000026: # AMBG = 1 -TAN(PSI)COS(PHI) TAN(PSI)SIN(PHI)
045183,000027: # 0 COS(PHI)/COS(PSI) -SIN(PHI)/COS(PSI)
045184,000028: # 0 SIN(PHI) COS(PHI)
045185,000029:
045186,000030: # WHERE PHI AND PSI ARE CDU ANGLES
045187,000031:
045188,000032: 20,3612 BANK 20
045189,000033: 22,2000 SETLOC DAPS8
045190,000034: 22,2000 BANK
045191,000035:
045192,000036: 22,3447 COUNT* $$/DAPEX
045193,000037: 22,3447 E6,1510 EBANK= KMPAC
045194,000038: 22,3447 30102 AMBGUPDT CA FLAGWRD6 # CHECK FOR RCS AUTOPILOT
045195,000039: 22,3450 00006 EXTEND
045196,000040: 22,3451 65217 BZMF ENDOFJOB # BIT15 = 0, BIT14 = 1
045197,000041: 22,3452 75002 MASK BIT14 # IF NOT RCS, EXIT
045198,000042: 22,3453 00006 EXTEND
045199,000043: 22,3454 15217 BZF ENDOFJOB # TO PROTECT TVC DAP ON SWITCHOVER
045200,000044:
045201,000045: 22,3455 30034 CA CDUZ
045202,000046: 22,3456 05075 TC SPSIN2
045203,000047: 22,3457 55640 TS AMGB1 # CALCULATE AMGB
045204,000048: 22,3460 30034 CA CDUZ
045205,000049: 22,3461 05074 TC SPCOS2
045206,000050: 22,3462 55645 TS CAPSI # MUST CHECK FOR GIMBAL LOCK
045207,000051: 22,3463 33507 CAF QUADANGL # = 7.25 DEGREES JET QUAD ANGULAR OFFSET
045208,000052: 22,3464 00006 EXTEND
045209,000053: 22,3465 20032 MSU CDUX
045210,000054: 22,3466 40000 COM # CDUX - 7.25 DEG
045211,000055: 22,3467 05074 TC SPCOS1
045212,000056: 22,3470 55644 TS AMGB8
045213,000057: 22,3471 00006 EXTEND
045214,000058: 22,3472 71645 MP CAPSI
045215,000059: 22,3473 55641 TS AMGB4
045216,000060: 22,3474 33507 CAF QUADANGL
045217,000061: 22,3475 00006 EXTEND
045218,000062: 22,3476 20032 MSU CDUX
045219,000063: 22,3477 40000 COM # CDUX - 7.25 DEG
045220,000064: 22,3500 05075 TC SPSIN1
045221,000065: 22,3501 55642 TS AMGB5
045222,000066: 22,3502 00006 EXTEND
045223,000067: 22,3503 71645 MP CAPSI
045224,000068: 22,3504 40000 COM
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Page 1038
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045226,000070: 22,3505 55643 TS AMGB7
045227,000071: 22,3506 15217 TCF ENDOFJOB
045228,000072: 22,3507 01224 QUADANGL DEC 660 B-14 # = 7.25 DEGREES
045229,000073:
End of include-file RCS-CSM_DAP_EXECUTIVE_PROGRAMS.agc. Parent file is MAIN.agc