Source Code
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These source-code files are part of a reconstructed copy of Skylark 048, the
Block II Command Module (CM) Apollo Guidance Computer (AGC) software for the
Skylab-2, Skylab-3, Skylab-4, and Apollo-Soyuz Test Project missions.
They have been created via disassembly of binary dumps of the original core rope
memory modules actually flown on Skylab-2, part numbers 2010802-541, 2010802-551,
2010802-561, 2010802-571, 2010802-581, and 2010802-591. Access to these modules
was provided by the New Mexico Museum of Space History, who we are much indebted to.
The source code for the Apollo 15, 16, and 17 software, Artemis 072, was used as
a starting point. Heavy use was made of TRW 4900.5-244, Programmed Guidance Equations
for Skylark Command Module Earth Orbital Program, dated 14 February 1972. This document
contains pseudocode of essentially all of Skylark, using original program labels which
have been copied for this source reconstruction.
Since only binary dumps (rather than listings) of Skylark are available as source material,
all comments and labels are approximate.
They have been taken from the Programmed Guidance Equations or other AGC programs where
possible, or, in some places, written from scratch to match what we believe would have
been in the original listing.
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042806,000002: ## Copyright: Public domain.
042807,000003: ## Filename: RCS-CSM_DAP_EXECUTIVE_PROGRAMS.agc
042808,000004: ## Purpose: A section of Skylark revision 048.
042809,000005: ## It is part of the source code for the Apollo Guidance Computer (AGC)
042810,000006: ## for Skylab-2, Skylab-3, Skylab-4, and ASTP. No original listings of
042811,000007: ## this software are available; instead, this file was created via
042812,000008: ## disassembly of dumps of the core rope modules actually flown on
042813,000009: ## Skylab-2. Access to these modules was provided by the New Mexico
042814,000010: ## Museum of Space History.
042815,000011: ## Assembler: yaYUL
042816,000012: ## Contact: Ron Burkey <info@sandroid.org>.
042817,000013: ## Website: www.ibiblio.org/apollo/index.html
042818,000014: ## Mod history: 2023-09-04 MAS Created from Artemis 072.
042819,000015:
042820,000016: # CALCULATION OF AMGB, AMBG ONCE EVERY SECOND
042821,000017:
042822,000018: # AMGB = 1 SIN(PSI) 0
042823,000019: # 0 COS(PSI)COS(PHI) SIN(PHI)
042824,000020: # 0 -COS(PSI)SIN(PHI) COS(PHI)
042825,000021:
042826,000022: # AMBG = 1 -TAN(PSI)COS(PHI) TAN(PSI)SIN(PHI)
042827,000023: # 0 COS(PHI)/COS(PSI) -SIN(PHI)/COS(PSI)
042828,000024: # 0 SIN(PHI) COS(PHI)
042829,000025:
042830,000026: # WHERE PHI AND PSI ARE CDU ANGLES
042831,000027:
042832,000028: 22,2000 SETLOC DAPS8
042833,000029: 22,2000 BANK
042834,000030:
042835,000031: 22,3522 COUNT* $$/DAPEX
042836,000032: 22,3522 E6,1537 EBANK= KMPAC
042837,000033: 22,3522 30102 AMBGUPDT CA FLAGWRD6 # CHECK FOR RCS AUTOPILOT
042838,000034: 22,3523 74076 MASK DPCONFIG
042839,000035: 22,3524 00006 EXTEND
042840,000036: 22,3525 65220 BZMF ENDOFJOB # BIT15 = 0, BIT14 = 1
042841,000037: 22,3526 74764 MASK DAP2BIT # IF NOT RCS, EXIT
042842,000038: 22,3527 00006 EXTEND
042843,000039: 22,3530 15220 BZF ENDOFJOB # TO PROTECT TVC DAP ON SWITCHOVER
042844,000040:
042845,000041: 22,3531 30034 CA CDUZ
042846,000042: 22,3532 05074 TC SPSIN2
042847,000043: 22,3533 55671 TS AMGB1 # CALCULATE AMGB
042848,000044: 22,3534 30034 CA CDUZ
042849,000045: 22,3535 05073 TC SPCOS2
042850,000046: 22,3536 55676 TS CAPSI # MUST CHECK FOR GIMBAL LOCK
042851,000047: 22,3537 34631 CAF QUADANGL # = 7.25 DEGREES JET QUAD ANGULAR OFFSET
042852,000048: 22,3540 00006 EXTEND
042853,000049: 22,3541 20032 MSU CDUX
042854,000050: 22,3542 40000 COM # CDUX - 7.25 DEG
042855,000051: 22,3543 05073 TC SPCOS1
042856,000052: 22,3544 55675 TS AMGB8
042857,000053: 22,3545 00006 EXTEND
042858,000054: 22,3546 71676 MP CAPSI
042859,000055: 22,3547 55672 TS AMGB4
042860,000056: 22,3550 34631 CAF QUADANGL
042861,000057: 22,3551 00006 EXTEND
042862,000058: 22,3552 20032 MSU CDUX
042863,000059: 22,3553 40000 COM # CDUX - 7.25 DEG
042864,000060: 22,3554 05074 TC SPSIN1
042865,000061: 22,3555 55673 TS AMGB5
042866,000062: 22,3556 00006 EXTEND
042867,000063: 22,3557 71676 MP CAPSI
042868,000064: 22,3560 40000 COM
042869,000065: 22,3561 55674 TS AMGB7
042870,000066: 22,3562 15220 TCF ENDOFJOB
042871,000067: 4000 SETLOC FFTAG12
042872,000068: 4000 BANK
042873,000069:
042874,000070: 4631 COUNT* $$/DAPEX
042875,000071: 4631 01224 QUADANGL DEC 660 B-14 # = 7.25 DEGREES
End of include-file RCS-CSM_DAP_EXECUTIVE_PROGRAMS.agc. Parent file is MAIN.agc