Source Code
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These source-code files are part of a reconstructed copy of LM131 revision 1,
the final release of the Apollo 13 Lunar Module (LM) Apollo Guidance Computer
(AGC) software.
The source reconstruction began with source code of Luminary 131 previously
transcribed from a digitized copy of that program. A dump of the flight spare
core rope memory module B5, part number 2010802-171, serial number RAY 411,
was obtained. This module is the only module different between Luminary 131
and LM131 revision 1. The dump was disassembled and all changes were incorporated
into these source files. Note that page numbers in the reconstructed code match
those on the Luminary 131 printout, although the changed code would likely have
changed page numbers for a real LM131 revision 1 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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041835,000002: ## Copyright: Public domain.
041836,000003: ## Filename: LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc
041837,000004: ## Purpose: A section of LM131 revision 1.
041838,000005: ## It is part of the reconstructed source code for the final
041839,000006: ## release of the flight software for the Lunar Module's (LM)
041840,000007: ## Apollo Guidance Computer (AGC) for Apollo 13. The code has
041841,000008: ## been reconstructed from a listing of Luminary 131 and a dump
041842,000009: ## of a core rope memory module B5, part number 2010802-171,
041843,000010: ## which is the only module different between LM131 revision 1
041844,000011: ## and Luminary 131. The executable generated from this source
041845,000012: ## has been verified against the module dump, so while the names,
041846,000013: ## comments, and ordering may not be exactly correct, the
041847,000014: ## resulting binary is.
041848,000015: ## Reference: pp. 978-981
041849,000016: ## Assembler: yaYUL
041850,000017: ## Contact: Ron Burkey <info@sandroid.org>.
041851,000018: ## Website: www.ibiblio.org/apollo/index.html
041852,000019: ## Mod history: 2022-10-28 MAS Created from Luminary 131.
041853,000020:
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Page 978
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041855,000022: # NAME - LSPOS - LOCATE SUN AND MOON DATE - 25 OCT 67
041856,000023: # MOD NO.1
041857,000024: # MOD BY NEVILLE ASSEMBLY SUNDANCE
041858,000025:
041859,000026: # FUNCTIONAL DESCRIPTION
041860,000027:
041861,000028: # COMPUTES UNIT POSITION VECTOR OF THE SUN AND MOON IN THE BASIC REFERENCE SYSTEM. THE SUN VECTOR S IS
041862,000029: # LOCATED VIA TWO ANGLES. THE FIRST ANGLE (OBLIQUITY) IS THE ANGLE BETWEEN THE EARTH EQUATOR AND THE ECLIPTIC. THE
041863,000030: # SECOND ANGLE IS THE LONGITUDE OF THE SUN MEASURED IN THE ECLIPTIC.
041864,000031: # THE POSITION VECTOR OF THE SUN IS
041865,000032: # -
041866,000033: # S = (COS(LOS), COS(OBL)*SIN(LOS), SIN(OBL)*SIN(LOS)), WHERE
041867,000034:
041868,000035: # LOS = LOS +LOS *T-(C *SIN(2PI*T)/365.24 +C *COS(2PI*T)/365.24)
041869,000036: # 0 R 0 1
041870,000037: # LOS (RAD) IS THE LONGITUDE OF THE SUN FOR MIDNIGHT JUNE 30TH OF THE PARTICULAR YEAR.
041871,000038: # 0
041872,000039: # LOS (RAD/DAY) IS THE MEAN RATE FOR THE PARTICULAR YEAR.
041873,000040: # R
041874,000041:
041875,000042: # LOS AND LOS ARE STORED AS LOSC AND LOSR IN RATESP.
041876,000043: # 0 R
041877,000044: # COS(OBL) AND SIN(OBL) ARE STORED IN THE MATRIX KONMAT.
041878,000045:
041879,000046: # T, TIME MEASURED IN DAYS (24 HOURS), IS STORED IN TIMEP.
041880,000047:
041881,000048: # C AND C ARE FUDGE FACTORS TO MINIMIZE THE DEVIATION. THEY ARE STORED AS ONE CONSTANT (CMOD), SINCE
041882,000049: # 0 1 2 2 1/2
041883,000050: # C *SIN(X)+C *COS(X) CAN BE WRITTEN AS (C +C ) *SIN(X+PHI), WHERE PHI=ARCTAN(C /C ).
041884,000051: # 0 1 0 1 1 0
041885,000052:
041886,000053: # THE MOON IS LOCATED VIA FOUR ANGLES. THE FIRST IS THE OBLIQUITY. THE SECOND IS THE MEAN LONGITUDE OF THE MOON,
041887,000054: # MEASURED IN THE ECLIPTIC FROM THE MEAN EQUINOX TO THE MEAN ASCENDING NODE OF THE LUNAR ORBIT, AND THEN ALONG THE
041888,000055: # ORBIT. THE THIRD ANGLE IS THE ANGLE BETWEEN THE ECLIPTIC AND THE LUNAR ORBIT. THE FOURTH ANGLE IS THE LONGITUDE
041889,000056: # OF THE NODE OF THE MOON, MEASURED IN THE LUNAR ORBIT. LET THESE ANGLES BE OBL,LOM,IM, AND LON RESPECTIVELY.
041890,000057:
041891,000058: # THE SIMPLIFIED POSITION VECTOR OF THE MOON IS
041892,000059: # -
041893,000060: # 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))
041894,000061:
041895,000062: # WHERE
041896,000063: # 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
041897,000064: # 0 R 0 1 0 1
041898,000065: # LON=LON +LON
041899,000066: # 0 R
041900,000067: # A , A , B AND B ARE STORED AS AMOD AND BMOD (SEE DESCRIPTION OF CMOD, ABOVE). COS(OBL), SIN(OBL)*SIN(IM),
041901,000068: # 0 1 0 1
041902,000069: # SIN(OBL), AND COS(OBL)*SIN(IM) ARE STORED IN KONMAT AS K1, K2, K3 AND K4, RESPECTIVELY. LOM , LOM , LON , LON
041903,000070: # ARE STORED AS LOMO, LOMR, LONO, AND LONR IN RATESP. 0 R 0 R
041904,000071:
041905,000072: # THE THREE PHIS ARE STORED AS AARG, BARG, AND CARG(SUN). ALL CONSTANTS ARE UPDATED BY YEAR.
041906,000073:
041907,000074: # CALLING SEQUENCE
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Page 979
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041909,000076: # CALL LSPOS. RETURN IS VIA CPRET.
041910,000077:
041911,000078: # ALARMS OR ABORTS
041912,000079: # NONE
041913,000080:
041914,000081: # ERASABLE INITIALIZATION REQUIRED
041915,000082: # TEPHEM - TIME FROM MIDNIGHT 1 JULY PRECEDING THE LAUNCH TO THE TIME OF THE LAUNCH (WHEN THE AGC CLOCK WENT
041916,000083: # TO ZERO). TEPHEM IS TP WITH UNITS OF CENTI-SECONDS.
041917,000084:
041918,000085: # TIME2 AND TIME1 ARE IN MPAC AND MPAC +1 WHEN PROGRAM IS CALLED.
041919,000086:
041920,000087: # OUTPUT
041921,000088: # UNIT POSITIONAL VECTOR OF SUN IN VSUN. (SCALED B-1)
041922,000089: # UNIT POSITIONAL VECTOR OF MOON IN VMOON. (SCALED B-1)
041923,000090:
041924,000091: # SUBROUTINES USED
041925,000092: # NONE
041926,000093:
041927,000094: # DEBRIS
041928,000095: # CURRENT CORE SET, WORK AREA AND FREEFLAG
041929,000096:
041930,000097: 04,2773 BANK 04
041931,000098: 15,2000 SETLOC EPHEM
041932,000099: 15,2000 BANK
041933,000100:
041934,000101: 15,3647 E5,1714 EBANK= VSUN
041935,000102: 15,3647 COUNT* $$/EPHEM
041936,000103: 15,3647 15,3647 LUNPOS EQUALS LSPOS
041937,000104:
041938,000105: 15,3647 54201 LSPOS SETPD SR
041939,000106: 15,3650 00001 0
041940,000107: 15,3651 20617 14D # TP
041941,000108: 15,3652 56371 TAD DDV
041942,000109: 15,3653 01707 TEPHEM # TIME OF LAUNCH
041943,000110: 15,3654 12024 CSTODAY # 24 HOURS-8640000 CENTI-SECS/DAY B-33
041944,000111: 15,3655 00031 STORE TIMEP # T IN DAYS
041945,000112: 15,3656 77170 AXT,1 AXT,2
041946,000113: 15,3657 00000 0
041947,000114: 15,3660 00000 0
041948,000115: 15,3661 77614 CLEAR
041949,000116: 15,3662 00274 FREEFLAG # SWITCH BIT
041950,000117: 15,3663 77745 POSITA DLOAD
041951,000118: 15,3664 12004 KONMAT +2 # ZEROS
041952,000119: 15,3665 00027 STORE GTMP
041953,000120: 15,3666 40745 POSITB DLOAD DMP*
041954,000121: 15,3667 00031 TIMEP # T
041955,000122: 15,3670 12050 VAL67 +4,1 # 1/27 OR 1/32 OR 1/365
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Page 980
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041957,000124: 15,3671 42661 SL DAD*
041958,000125: 15,3672 20211 8D
041959,000126: 15,3673 12046 VAL67 +2,1 # AARG
041960,000127: 15,3674 40756 SIN DMP* # SIN(T/27+PHI) OR T/32 OR T/365
041961,000128: 15,3675 12044 VAL67,1 # (A0**2+A1**2)**1/2 SIN(X+PHIA)
041962,000129: 15,3676 62015 DAD INCR,1 # PLUS
041963,000130: 15,3677 00027 GTMP # (B0**2+B1**2)**1/2 SIN(X+PHIB)
041964,000131: 15,3700 77771 DEC -6 B-14
041965,000132: 15,3701 00027 STORE GTMP # OR (C0**2+C1**2)**1/2 SIN(X+PHIC)
041966,000133: 15,3702 77614 BOFSET
041967,000134: 15,3703 00054 FREEFLAG
041968,000135: 15,3704 33666 POSITB
041969,000136: 15,3705 40745 POSITD DLOAD DMP*
041970,000137: 15,3706 00031 TIMEP # T
041971,000138: 15,3707 65747 RATESP,2 # LOMR,LOSR,LONR
041972,000139: 15,3710 42661 SL DAD*
041973,000140: 15,3711 20206 5D
041974,000141: 15,3712 65741 RATESP +6,2 # LOMO,LOSO,LONO
041975,000142: 15,3713 77625 DSU
041976,000143: 15,3714 00027 GTMP
041977,000144: 15,3715 10021 STORE STMP,2 # LOM,LOS,LON
041978,000145: 15,3716 63135 SLOAD INCR,2
041979,000146: 15,3717 00050 X2
041980,000147: 15,3720 77775 DEC -2 B-14
041981,000148: 15,3721 53015 DAD BZE
041982,000149: 15,3722 12026 RCB-13 # PLUS 2
041983,000150: 15,3723 33753 POSITE # 2ND
041984,000151: 15,3724 77644 BPL
041985,000152: 15,3725 33663 POSITA # 1ST
041986,000153: 15,3726 45345 POSITF DLOAD DSU # 3RD
041987,000154: 15,3727 00021 STMP # LOM
041988,000155: 15,3730 00025 STMP +4 # LON
041989,000156: 15,3731 65356 SIN PDDL # SIN(LOM-LON)
041990,000157: 15,3732 00021 STMP
041991,000158: 15,3733 65356 SIN PDDL # SIN LOM
041992,000159: 15,3734 00021 STMP
041993,000160: 15,3735 55546 COS VDEF # COS LOM
041994,000161: 15,3736 53521 MXV UNIT
041995,000162: 15,3737 12002 KONMAT # K1,K2,K3,K4,
041996,000163: 15,3740 02723 STORE VMOON
041997,000164: 15,3741 65345 DLOAD PDDL
041998,000165: 15,3742 12004 KONMAT +2 # ZERO
041999,000166: 15,3743 00023 STMP +2
042000,000167: 15,3744 65356 SIN PDDL # SIN LOS
042001,000168: 15,3745 00023 STMP +2
042002,000169: 15,3746 55546 COS VDEF # COS LOS
042003,000170: 15,3747 53521 MXV UNIT
042004,000171: 15,3750 12002 KONMAT
042005,000172: 15,3751 02715 STORE VSUN
042006,000173: 15,3752 77616 RVQ
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Page 981
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042008,000175: 15,3753 77745 POSITE DLOAD
042009,000176: 15,3754 12004 KONMAT +2 # ZEROS
042010,000177: 15,3755 00027 STORE GTMP
042011,000178: 15,3756 77650 GOTO
042012,000179: 15,3757 33705 POSITD
042013,000180: 05,2000 SETLOC EPHEM1
042014,000181: 05,2000 BANK
042015,000182:
042016,000183: 05,3505 COUNT* $$/EPHEM
042017,000184: 05,3505 STMP EQUALS 16D
042018,000185: 05,3505 GTMP EQUALS 22D
042019,000186: 05,3505 TIMEP EQUALS 24D
042020,000187:
End of include-file LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc. Parent file is MAIN.agc