Source Code
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These source-code files are part of a reconstructed copy of Luminary 69/2,
the flown, final release of the Apollo 10 Lunar Module (LM) Apollo Guidance Computer (AGC) software.
The reconstruction is based on the source code of Luminary 69 — i.e., the
initial, unflown version, "revision 0" — of which
a contemporary listing was available. The code was then updated by incorporating the
differences between Luminary 69 and Luminary 69/2, known from other contemporary
documentation. The only such difference is the implementation in
Luminary 69/2 of the "R-2 Lunar Potential Model", the source code for which was taken
from program Luminary 99/1 (Apollo 11 LM), of which a contemporary listing was also available.
Finally, the now-reconstructed Luminary 69/2 was then validated by assembling it to
executable form and verifying that its memory banks had the correct checksums,
known from still other contemporary documentation.
Note that page numbers in the reconstructed code match those in the original Luminary 69
program listing, or in the ORBITAL INTEGRATION log section, in Luminary 99/1. Page numbers
would certainly differ somewhat in a contemporary Luminary 69/2 listing.
Moreover, annotations that were not present in the contemporary source code have been added
to the reconstructed code to justify each change in Luminary 69/2 relative to
Luminary 69. Here's a guide to the Apollo documentation referenced in those annotations:
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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043043,000002: ## Copyright: Public domain.
043044,000003: ## Filename: LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc
043045,000004: ## Purpose: A section of LUM69 revision 2.
043046,000005: ## It is part of the reconstructed source code for the flown
043047,000006: ## version of the flight software for the Lunar Module's (LM)
043048,000007: ## Apollo Guidance Computer (AGC) for Apollo 10. The code has
043049,000008: ## been recreated from a copy of Luminary revsion 069, using
043050,000009: ## changes present in Luminary 099 which were described in
043051,000010: ## Luminary memos 75 and 78. The code has been adapted such
043052,000011: ## that the resulting bugger words exactly match those specified
043053,000012: ## for LUM69 revision 2 in NASA drawing 2021152B, which gives
043054,000013: ## relatively high confidence that the reconstruction is correct.
043055,000014: ## Reference: pp. 979-982
043056,000015: ## Assembler: yaYUL
043057,000016: ## Contact: Ron Burkey <info@sandroid.org>.
043058,000017: ## Website: www.ibiblio.org/apollo/index.html
043059,000018: ## Mod history: 2019-07-27 MAS Created from Luminary 69.
043060,000019:
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Page 979
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043062,000021: # NAME - LSPOS - LOCATE SUN AND MOON DATE - 25 OCT 67
043063,000022: # MOD NO.1
043064,000023: # MOD BY NEVILLE ASSEMBLY SUNDANCE
043065,000024:
043066,000025: # FUNCTIONAL DESCRIPTION
043067,000026:
043068,000027: # COMPUTES UNIT POSITION VECTOR OF THE SUN AND MOON IN THE BASIC REFERENCE SYSTEM. THE SUN VECTOR S IS
043069,000028: # LOCATED VIA TWO ANGLES. THE FIRST ANGLE(OBLIQUITY) IS THE ANGLE BETWEEN THE EARTH EQUATOR AND THE ECLIPTIC. THE
043070,000029: # SECOND ANGLE IS THE LONGITUDE OF THE SUN MEASURED IN THE ECLIPTIC.
043071,000030: # THE POSITION VECTOR OF THE SUN IS
043072,000031: # -
043073,000032: # S = (COS(LOS), COS(OBL)*SIN(LOS), SIN(OBL)*SIN(LOS)), WHERE
043074,000033:
043075,000034: # LOS = LOS +LOS *T-(C *SIN(2PI*T)/365.24 +C *COS(2PI*T)/365.24)
043076,000035: # 0 R 0 1
043077,000036: # LOS (RAD) IS THE LONGITUDE OF THE SUN FOR MIDNIGHT JUNE 30TH OF THE PARTICULAR YEAR.
043078,000037: # 0
043079,000038: # LOS (RAD/DAY) IS THE MEAN RATE FOR THE PARTICULAR YEAR.
043080,000039: # R
043081,000040:
043082,000041: # LOS AND LOS ARE STORED AS LOSC AND LOSR IN RATESP.
043083,000042: # 0 R
043084,000043: # COS(OBL) AND SIN(OBL) ARE STORED IN THE MATRIX KONMAT.
043085,000044: # T, TIME MEASURED IN DAYS (24 HOURS), IS STORED IN TIMEP.
043086,000045: # C AND C ARE FUDGE FACTORS TO MINIMIZE THE DEVIATION. THEY ARE STORED AS ONE CONSTANT (CMOD), SINCE
043087,000046: # 0 1 2 2 1/2
043088,000047: # C *SIN(X)+C *COS(X) CAN BE WRITTEN AS (C +C ) *SIN(X+PHI), WHERE PHI=ARCTAN(C /C ).
043089,000048: # 0 1 0 1 1 0
043090,000049:
043091,000050: # THE MOON IS LOCATED VIA FOUR ANGLES. THE FIRST IS THE OBLIQUITY. THE SECOND IS THE MEAN LONGITUDE OF THE MOON,
043092,000051: # MEASURED IN THE ECLIPTIC FROM THE MEAN EQUINOX TO THE MEAN ASCENDING NODE OF THE LUNAR ORBIT, AND THEN ALONG THE
043093,000052: # ORBIT. THE THIRD ANGLE IS THE ANGLE BETWEEN THE ECLIPTIC AND THE LUNAR ORBIT. THE FOURTH ANGLE IS THE LONGITUDE
043094,000053: # OF THE NODE OF THE MOON, MEASURED IN THE LUNAR ORBIT. LET THESE ANGLES BE OBL,LOM,IM, AND LON RESPECTIVELY.
043095,000054:
043096,000055: # THE SIMPLIFIED POSITION VECTOR OF THE MOON IS
043097,000056: # -
043098,000057: # M=(COS(LOM), COS(OBL)*SIN(LOM)-SIN(OBL)*SIN(IM)*SIN(LOM-LON), SIN(OBL)*SIN(LOM)+COS(OBL)*SIN(IM)*SIN(LOM-LON))
043099,000058:
043100,000059: # WHERE
043101,000060: # LOM=LOM +LOM *T-(A *SIN 2PI*T/27.5545+A *COS(2PI*T/27.5545)+B *SIN 2PI*T/32+B *COS(2PI*T/32)), AND
043102,000061: # 0 R 0 1 0 1
043103,000062: # LON=LON +LON
043104,000063: # 0 R
043105,000064: # A , A , B AND B ARE STORED AS AMOD AND BMOD (SEE DESCRIPTION OF CMOD, ABOVE). COS(OBL), SIN(OBL)*SIN(IM),
043106,000065: # 0 1 0 1
043107,000066: # SIN(OBL), AND COS(OBL)*SIN(IM) ARE STORED IN KONMAT AS K1, K2, K3 AND K4, RESPECTIVELY. LOM , LOM , LON , LON
043108,000067: # ARE STORED AS LOMO, LOMR, LONO, AND LONR IN RATESP. 0 R 0 R
043109,000068: # THE THREE PHIS ARE STORED AS AARG, BARG, AND CARG(SUN). ALL CONSTANTS ARE UPDATED BY YEAR.
043110,000069:
043111,000070: # CALLING SEQUENCE
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Page 980
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043113,000072: # CALL LSPOS. RETURN IS VIA CPRET.
043114,000073:
043115,000074: # ALARMS OR ABORTS
043116,000075: # NONE
043117,000076:
043118,000077: # ERASABLE INITIALIZATION REQUIRED
043119,000078: # TEPHEM - TIME FROM MIDNIGHT 1 JULY PRECEDING THE LAUNCH TO THE TIME OF THE LAUNCH (WHEN THE AGC CLOCK WENT
043120,000079: # TO ZERO). TEPHEM IS TP WITH UNITS OF CENTI-SECONDS.
043121,000080:
043122,000081: # TIME2 AND TIME1 ARE IN MPAC AND MPAC +1 WHEN PROGRAM IS CALLED.
043123,000082:
043124,000083: # OUTPUT
043125,000084: # UNIT POSITIONAL VECTOR OF SUN IN VSUN. (SCALED B-1)
043126,000085: # UNIT POSITIONAL VECTOR OF MOON IN VMOON. (SCALED B-1)
043127,000086:
043128,000087: # SUBROUTINES USED
043129,000088: # NONE
043130,000089:
043131,000090: # DEBRIS
043132,000091: # CURRENT CORE SET, WORK AREA AND FREEFLAG
043133,000092:
043134,000093: 04,2750 BANK 04
043135,000094: 15,2000 SETLOC EPHEM
043136,000095: 15,2000 BANK
043137,000096:
043138,000097: 15,3663 E5,1714 EBANK= VSUN
043139,000098: 15,3663 COUNT* $$/EPHEM
043140,000099: 15,3663 15,3663 LUNPOS EQUALS LSPOS
043141,000100:
043142,000101: 15,3663 54201 LSPOS SETPD SR
043143,000102: 15,3664 00001 0
043144,000103: 15,3665 20617 14D # TP
043145,000104: 15,3666 56371 TAD DDV
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In Lum99, the hand-written notation "in centisec B 42" appears to the right.
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043147,000106: 15,3667 01707 TEPHEM # TIME OF LAUNCH
043148,000107: 15,3670 12024 CSTODAY # 24 HOURS-8640000 CENTI-SECS/DAY B-33
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In Lum99, the hand-written notation "@ B 9 = 512 days" appears to the right.
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043150,000109: 15,3671 00031 STORE TIMEP # T IN DAYS
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In Lum99, the hand-written notation "∴ granularity ≈ 0.164 sec" appears to the right.
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043152,000111: 15,3672 77170 AXT,1 AXT,2
043153,000112: 15,3673 00000 0
043154,000113: 15,3674 00000 0
043155,000114: 15,3675 77614 CLEAR
043156,000115: 15,3676 00274 FREEFLAG # SWITCH BIT
043157,000116: 15,3677 77745 POSITA DLOAD
043158,000117: 15,3700 12004 KONMAT +2 # ZEROS
043159,000118: 15,3701 00027 STORE GTMP
043160,000119: 15,3702 40745 POSITB DLOAD DMP*
043161,000120: 15,3703 00031 TIMEP # T
043162,000121: 15,3704 12050 VAL67 +4,1 # 1/27 OR 1/32 OR 1/365
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Page 981
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043164,000123: 15,3705 42661 SL DAD*
043165,000124: 15,3706 20211 8D
043166,000125: 15,3707 12046 VAL67 +2,1 # AARG
043167,000126: 15,3710 40756 SIN DMP* # SIN(T/27+PHI) OR T/32 OR T/365
043168,000127: 15,3711 12044 VAL67,1 # (A0**2+A1**2)**1/2 SIN(X+PHIA)
043169,000128: 15,3712 62015 DAD INCR,1 # PLUS
043170,000129: 15,3713 00027 GTMP # (B0**2+B1**2)**1/2 SIN(X+PHIB)
043171,000130: 15,3714 77771 DEC -6 B-14
043172,000131: 15,3715 00027 STORE GTMP # OR (C0**2+C1**2)**1/2 SIN(X+PHIC)
043173,000132: 15,3716 77614 BOFSET
043174,000133: 15,3717 00054 FREEFLAG
043175,000134: 15,3720 33702 POSITB
043176,000135: 15,3721 40745 POSITD DLOAD DMP*
043177,000136: 15,3722 00031 TIMEP # T
043178,000137: 15,3723 65747 RATESP,2 # LOMR,LOSR,LONR
043179,000138: 15,3724 42661 SL DAD*
043180,000139: 15,3725 20206 5D
043181,000140: 15,3726 65741 RATESP +6,2 # LOMO,LOSO,LONO
043182,000141: 15,3727 77625 DSU
043183,000142: 15,3730 00027 GTMP
043184,000143: 15,3731 10021 STORE STMP,2 # LOM,LOS,LON
043185,000144: 15,3732 63135 SLOAD INCR,2
043186,000145: 15,3733 00050 X2
043187,000146: 15,3734 77775 DEC -2 B-14
043188,000147: 15,3735 53015 DAD BZE
043189,000148: 15,3736 12026 RCB-13 # PLUS 2
043190,000149: 15,3737 33767 POSITE # 2ND
043191,000150: 15,3740 77644 BPL
043192,000151: 15,3741 33677 POSITA # 1ST
043193,000152: 15,3742 45345 POSITF DLOAD DSU # 3RD
043194,000153: 15,3743 00021 STMP # LOM
043195,000154: 15,3744 00025 STMP +4 # LON
043196,000155: 15,3745 65356 SIN PDDL # SIN(LOM-LON)
043197,000156: 15,3746 00021 STMP
043198,000157: 15,3747 65356 SIN PDDL # SIN LOM
043199,000158: 15,3750 00021 STMP
043200,000159: 15,3751 55546 COS VDEF # COS LOM
043201,000160: 15,3752 53521 MXV UNIT
043202,000161: 15,3753 12002 KONMAT # K1,K2,K3,K4,
043203,000162: 15,3754 02723 STORE VMOON
043204,000163: 15,3755 65345 DLOAD PDDL
043205,000164: 15,3756 12004 KONMAT +2 # ZERO
043206,000165: 15,3757 00023 STMP +2
043207,000166: 15,3760 65356 SIN PDDL # SIN LOS
043208,000167: 15,3761 00023 STMP +2
043209,000168: 15,3762 55546 COS VDEF # COS LOS
043210,000169: 15,3763 53521 MXV UNIT
043211,000170: 15,3764 12002 KONMAT
043212,000171: 15,3765 02715 STORE VSUN
043213,000172: 15,3766 77616 RVQ
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Page 982
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043215,000174: 15,3767 77745 POSITE DLOAD
043216,000175: 15,3770 12004 KONMAT +2 # ZEROS
043217,000176: 15,3771 00027 STORE GTMP
043218,000177: 15,3772 77650 GOTO
043219,000178: 15,3773 33721 POSITD
043220,000179: 15,3774 77616 LUNVEL RVQ # TO FOOL INTEGRATION
043221,000180: 05,2000 SETLOC EPHEM1
043222,000181: 05,2000 BANK
043223,000182:
043224,000183: 05,3430 COUNT* $$/EPHEM
043225,000184: 05,3430 STMP EQUALS 16D
043226,000185:
043227,000186: 05,3430 GTMP EQUALS 22D
043228,000187:
043229,000188: 05,3430 TIMEP EQUALS 24D
043230,000189:
End of include-file LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc. Parent file is MAIN.agc