Source Code
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These source-code files are part of a reconstructed copy of Luminary 97, the
second release of the Apollo 11 Lunar Module (LM) Apollo Guidance Computer
(AGC) software. It was created to fix two incorrect ephemeris constants in
Luminary 96, as described by anomaly report LNY-59.
The reconstruction began with source code of Luminary 99 revision 1 previously
transcribed from a digitized copy of that program. The code was then updated
by undoing changes described in original Luminary memos 83 and 85, using asterisks
indicating changed lines in the listing as a guide. The reconstruction was
verified by matching memory-bank checksums to those listed in drawing 2021152D.
Note that page numbers in the reconstructed code match those on the Luminary 099
revision 001 printout, although the added code would likely have changed page
numbers for a real Luminary 97 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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014962,000002: ## Copyright: Public domain.
014963,000003: ## Filename: GIMBAL_LOCK_AVOIDANCE.agc
014964,000004: ## Purpose: A section of Luminary revision 97.
014965,000005: ## It is part of the reconstructed source code for the
014966,000006: ## second release of the flight software for the Lunar
014967,000007: ## Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
014968,000008: ## It was created to fix two incorrect ephemeris constants in
014969,000009: ## Luminary 96, as described by anomaly report LNY-59.
014970,000010: ## The code has been recreated from a copy of Luminary 99
014971,000011: ## revision 001, using asterisks indicating changed lines in
014972,000012: ## the listing and Luminary Memos #83 and #85, which list
014973,000013: ## changes between Luminary 97 and 98, and 98 and 99. The
014974,000014: ## code has been adapted such that the resulting bugger words
014975,000015: ## exactly match those specified for Luminary 97 in NASA drawing
014976,000016: ## 2021152D, which gives relatively high confidence that the
014977,000017: ## reconstruction is correct.
014978,000018: ## Reference: p. 364
014979,000019: ## Assembler: yaYUL
014980,000020: ## Contact: Ron Burkey <info@sandroid.org>.
014981,000021: ## Website: www.ibiblio.org/apollo/index.html
014982,000022: ## Mod history: 2019-07-28 MAS Created from Luminary 99.
014983,000023:
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Page 364
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014985,000025: 15,2050 BANK 15
014986,000026:
014987,000027: 22,2000 SETLOC KALCMON1
014988,000028: 22,2000 BANK
014989,000029:
014990,000030: # DETECTING GIMBAL LOCK
014991,000031: 22,2744 22,2744 LOCSKIRT EQUALS NOGIMLOC
014992,000032:
014993,000033: 22,2744 77614 NOGIMLOC SET
014994,000034: 22,2745 01074 CALCMAN3
014995,000035: 22,2746 70740 WCALC LXC,1 DLOAD*
014996,000036: 22,2747 01325 RATEINDX # CHOOSE THE DESIRED MANEUVER RATE
014997,000037: 22,2750 04772 ARATE,1 # FROM A LIST OF FOUR
014998,000038: 22,2751 45002 SR4 CALL # COMPUTE THE INCREMENTAL ROTATION MATRIX
014999,000039: 22,2752 44527 DELCOMP # DEL CORRESPONDING TO A 1 SEC ROTATION
015000,000040: # ABOUT COF
015001,000041: 22,2753 74343 DLOAD* VXSC
015002,000042: 22,2754 04772 ARATE,1
015003,000043: 22,2755 03271 COF
015004,000044: 22,2756 17326 STODL BRATE # COMPONENT MANEUVER RATES 45 DEG/SEC
015005,000045: 22,2757 03336 AM
015006,000046: 22,2760 55605 DMP DDV*
015007,000047: 22,2761 05002 ANGLTIME
015008,000048: 22,2762 04772 ARATE,1
015009,000049: 22,2763 77661 SR
015010,000050: 22,2764 20606 5
015011,000051: 22,2765 03334 STORE TM # MANEUVER EXECUTION TIME SCALED AS T2
015012,000052: 22,2766 77614 SETGO
015013,000053: 22,2767 01035 CALCMAN2 # 0(OFF) = CONTINUE MANEUVER
015014,000054: 22,2770 45010 NEWANGL +1 # 1(ON) = START MANEUVER
015015,000055:
015016,000056: # THE FOUR SELECTABLE FREE FALL MANEUVER RATES SELECTED BY
015017,000057: # LOADING RATEINDX WITH 0, 2, 4, 6, RESPECTIVELY
015018,000058:
015019,000059: 22,2771 00221 24255 ARATE 2DEC .0088888888 # = 0.2 DEG/SEC $ 22.5 DEG/SEC
015020,000060:
015021,000061: 22,2773 00554 02660 2DEC .0222222222 # = 0.5 DEG/SEC $ 22.5 DEG/SEC
015022,000062:
015023,000063: 22,2775 02660 13301 2DEC .0888888888 # = 2.0 DEG/SEC $ 22.5 DEG/SEC
015024,000064:
015025,000065: 22,2777 16161 30707 2DEC .4444444444 # = 10.0 DEG/SEC $ 22.5 DEG/SEC
015026,000066:
015027,000067: 22,3001 00003 04000 ANGLTIME 2DEC .0001907349 # = 100B-19 FUDGE FACTOR TO CONVERT
015028,000068: # MANEUVER ANGLE TO MANEUVER TIME
015029,000069:
015030,000070:
End of include-file GIMBAL_LOCK_AVOIDANCE.agc. Parent file is MAIN.agc