GAP: ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091 17:53 DEC. 19, 1969Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together.
Source Code
|
|
This source code is very close to the Apollo Guidance Computer software for the
Apollo 13 Lunar module. This revision of the Luminary 131 program is from December
of 1969, whereas there was a later revision in January of 1970, and still another
revision in February, which is the code that flew on the mission.
As far as this transcription is concerned, it was originally from a copy made in 1991 of
a printout from the collection of AGC developer Don Eyles for collector David Craig.
It was subsequently scanned by Gary Neff, reprocessed for online
presentation at the now-discontinued History of Recent Science and Technology (HRST) website
of MIT's Dibner Institute (the full-quality scans being discarded in the process),
and finally transcribed by Ron Burkey for the Virtual AGC Project. Although a
high-quality replacement scan for a completely illegible page was later provided by Gary
Neff, the reduced legibility of the reprocessed HRST posting nevertheless caused many
errors to be introduced into the transcription. Accordingly, a second scan of the same physical
printout was made in 2017 for the Virtual AGC Project's collection at the Internet Archive,
and used to correct the transcription errors. All of the scanned materials mentioned,
as well as other Luminary 131 related material, are available online.
Don Eyles apprently made additional hand-written notes in printout between 1991 and 2017,
so the two scans are not identical in that respect. The page-headings in the printout read, in part:GAP: ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091 17:53 DEC. 19, 1969Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together. |
041885,000002: ## Copyright: Public domain.
041886,000003: ## Filename: LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc
041887,000004: ## Purpose: A section of Luminary 1C, revision 131.
041888,000005: ## It is part of the source code for the Lunar Module's (LM)
041889,000006: ## Apollo Guidance Computer (AGC) for Apollo 13.
041890,000007: ## This file is intended to be a faithful transcription, except
041891,000008: ## that the code format has been changed to conform to the
041892,000009: ## requirements of the yaYUL assembler rather than the
041893,000010: ## original YUL assembler.
041894,000011: ## Reference: pp. 978-981
041895,000012: ## Contact: Ron Burkey <info@sandroid.org>.
041896,000013: ## Website: www.ibiblio.org/apollo/index.html
041897,000014: ## Mod history: 05/29/03 RSB. Began transcribing.
041898,000015: ## 05/14/05 RSB Corrected website reference above.
041899,000016: ## 2017-01-06 RSB Page numbers now agree with those on the
041900,000017: ## original hardcopy, as opposed to the PDF page
041901,000018: ## numbers in 1701.pdf.
041902,000019: ## 2017-02-26 RSB Proofed comment text using octopus/ProoferComments.
041903,000020: ## 2017-03-13 RSB Comment-text fixes noted in proofing Luminary 116.
041904,000021: ## 2017-08-26 MAS Fixed comment-text errors found while transcribing Zerlina 56.
041905,000022:
|
|
Page 978 |
041907,000024: # NAME - LSPOS - LOCATE SUN AND MOON DATE - 25 OCT 67
041908,000025: # MOD NO.1
041909,000026: # MOD BY NEVILLE ASSEMBLY SUNDANCE
041910,000027:
041911,000028: # FUNCTIONAL DESCRIPTION
041912,000029:
041913,000030: # COMPUTES UNIT POSITION VECTOR OF THE SUN AND MOON IN THE BASIC REFERENCE SYSTEM. THE SUN VECTOR S IS
041914,000031: # LOCATED VIA TWO ANGLES. THE FIRST ANGLE (OBLIQUITY) IS THE ANGLE BETWEEN THE EARTH EQUATOR AND THE ECLIPTIC. THE
041915,000032: # SECOND ANGLE IS THE LONGITUDE OF THE SUN MEASURED IN THE ECLIPTIC.
041916,000033: # THE POSITION VECTOR OF THE SUN IS
041917,000034: # -
041918,000035: # S = (COS(LOS), COS(OBL)*SIN(LOS), SIN(OBL)*SIN(LOS)), WHERE
041919,000036:
041920,000037: # LOS = LOS +LOS *T-(C *SIN(2PI*T)/365.24 +C *COS(2PI*T)/365.24)
041921,000038: # 0 R 0 1
041922,000039: # LOS (RAD) IS THE LONGITUDE OF THE SUN FOR MIDNIGHT JUNE 30TH OF THE PARTICULAR YEAR.
041923,000040: # 0
041924,000041: # LOS (RAD/DAY) IS THE MEAN RATE FOR THE PARTICULAR YEAR.
041925,000042: # R
041926,000043:
041927,000044: # LOS AND LOS ARE STORED AS LOSC AND LOSR IN RATESP.
041928,000045: # 0 R
041929,000046: # COS(OBL) AND SIN(OBL) ARE STORED IN THE MATRIX KONMAT.
041930,000047:
041931,000048: # T, TIME MEASURED IN DAYS (24 HOURS), IS STORED IN TIMEP.
041932,000049:
041933,000050: # C AND C ARE FUDGE FACTORS TO MINIMIZE THE DEVIATION. THEY ARE STORED AS ONE CONSTANT (CMOD), SINCE
041934,000051: # 0 1 2 2 1/2
041935,000052: # C *SIN(X)+C *COS(X) CAN BE WRITTEN AS (C +C ) *SIN(X+PHI), WHERE PHI=ARCTAN(C /C ).
041936,000053: # 0 1 0 1 1 0
041937,000054:
041938,000055: # THE MOON IS LOCATED VIA FOUR ANGLES. THE FIRST IS THE OBLIQUITY. THE SECOND IS THE MEAN LONGITUDE OF THE MOON,
041939,000056: # MEASURED IN THE ECLIPTIC FROM THE MEAN EQUINOX TO THE MEAN ASCENDING NODE OF THE LUNAR ORBIT, AND THEN ALONG THE
041940,000057: # ORBIT. THE THIRD ANGLE IS THE ANGLE BETWEEN THE ECLIPTIC AND THE LUNAR ORBIT. THE FOURTH ANGLE IS THE LONGITUDE
041941,000058: # OF THE NODE OF THE MOON, MEASURED IN THE LUNAR ORBIT. LET THESE ANGLES BE OBL,LOM,IM, AND LON RESPECTIVELY.
041942,000059:
041943,000060: # THE SIMPLIFIED POSITION VECTOR OF THE MOON IS
041944,000061: # -
041945,000062: # 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))
041946,000063:
041947,000064: # WHERE
041948,000065: # 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
041949,000066: # 0 R 0 1 0 1
041950,000067: # LON=LON +LON
041951,000068: # 0 R
041952,000069: # A , A , B AND B ARE STORED AS AMOD AND BMOD (SEE DESCRIPTION OF CMOD, ABOVE). COS(OBL), SIN(OBL)*SIN(IM),
041953,000070: # 0 1 0 1
041954,000071: # SIN(OBL), AND COS(OBL)*SIN(IM) ARE STORED IN KONMAT AS K1, K2, K3 AND K4, RESPECTIVELY. LOM , LOM , LON , LON
041955,000072: # ARE STORED AS LOMO, LOMR, LONO, AND LONR IN RATESP. 0 R 0 R
041956,000073:
041957,000074: # THE THREE PHIS ARE STORED AS AARG, BARG, AND CARG(SUN). ALL CONSTANTS ARE UPDATED BY YEAR.
041958,000075:
041959,000076: # CALLING SEQUENCE
|
|
Page 979 |
041961,000078: # CALL LSPOS. RETURN IS VIA CPRET.
041962,000079:
041963,000080: # ALARMS OR ABORTS
041964,000081: # NONE
041965,000082:
041966,000083: # ERASABLE INITIALIZATION REQUIRED
041967,000084: # TEPHEM - TIME FROM MIDNIGHT 1 JULY PRECEDING THE LAUNCH TO THE TIME OF THE LAUNCH (WHEN THE AGC CLOCK WENT
041968,000085: # TO ZERO). TEPHEM IS TP WITH UNITS OF CENTI-SECONDS.
041969,000086:
041970,000087: # TIME2 AND TIME1 ARE IN MPAC AND MPAC +1 WHEN PROGRAM IS CALLED.
041971,000088:
041972,000089: # OUTPUT
041973,000090: # UNIT POSITIONAL VECTOR OF SUN IN VSUN. (SCALED B-1)
041974,000091: # UNIT POSITIONAL VECTOR OF MOON IN VMOON. (SCALED B-1)
041975,000092:
041976,000093: # SUBROUTINES USED
041977,000094: # NONE
041978,000095:
041979,000096: # DEBRIS
041980,000097: # CURRENT CORE SET, WORK AREA AND FREEFLAG
041981,000098:
041982,000099: 04,2773 BANK 04
041983,000100: 15,2000 SETLOC EPHEM
041984,000101: 15,2000 BANK
041985,000102:
041986,000103: 15,3647 E5,1714 EBANK= VSUN
041987,000104: 15,3647 COUNT* $$/EPHEM
041988,000105: 15,3647 15,3647 LUNPOS EQUALS LSPOS
041989,000106:
041990,000107: 15,3647 54201 LSPOS SETPD SR
041991,000108: 15,3650 00001 0
041992,000109: 15,3651 20617 14D # TP
041993,000110: 15,3652 56371 TAD DDV
041994,000111: 15,3653 01707 TEPHEM # TIME OF LAUNCH
041995,000112: 15,3654 12024 CSTODAY # 24 HOURS-8640000 CENTI-SECS/DAY B-33
041996,000113: 15,3655 00031 STORE TIMEP # T IN DAYS
041997,000114: 15,3656 77170 AXT,1 AXT,2
041998,000115: 15,3657 00000 0
041999,000116: 15,3660 00000 0
042000,000117: 15,3661 77614 CLEAR
042001,000118: 15,3662 00274 FREEFLAG # SWITCH BIT
042002,000119: 15,3663 77745 POSITA DLOAD
042003,000120: 15,3664 12004 KONMAT +2 # ZEROS
042004,000121: 15,3665 00027 STORE GTMP
042005,000122: 15,3666 40745 POSITB DLOAD DMP*
042006,000123: 15,3667 00031 TIMEP # T
042007,000124: 15,3670 12050 VAL67 +4,1 # 1/27 OR 1/32 OR 1/365
|
|
Page 980 |
042009,000126: 15,3671 42661 SL DAD*
042010,000127: 15,3672 20211 8D
042011,000128: 15,3673 12046 VAL67 +2,1 # AARG
042012,000129: 15,3674 40756 SIN DMP* # SIN(T/27+PHI) OR T/32 OR T/365
042013,000130: 15,3675 12044 VAL67,1 # (A0**2+A1**2)**1/2 SIN(X+PHIA)
042014,000131: 15,3676 62015 DAD INCR,1 # PLUS
042015,000132: 15,3677 00027 GTMP # (B0**2+B1**2)**1/2 SIN(X+PHIB)
042016,000133: 15,3700 77771 DEC -6 B-14
042017,000134: 15,3701 00027 STORE GTMP # OR (C0**2+C1**2)**1/2 SIN(X+PHIC)
042018,000135: 15,3702 77614 BOFSET
042019,000136: 15,3703 00054 FREEFLAG
042020,000137: 15,3704 33666 POSITB
042021,000138: 15,3705 40745 POSITD DLOAD DMP*
042022,000139: 15,3706 00031 TIMEP # T
042023,000140: 15,3707 65747 RATESP,2 # LOMR,LOSR,LONR
042024,000141: 15,3710 42661 SL DAD*
042025,000142: 15,3711 20206 5D
042026,000143: 15,3712 65741 RATESP +6,2 # LOMO,LOSO,LONO
042027,000144: 15,3713 77625 DSU
042028,000145: 15,3714 00027 GTMP
042029,000146: 15,3715 10021 STORE STMP,2 # LOM,LOS,LON
042030,000147: 15,3716 63135 SLOAD INCR,2
042031,000148: 15,3717 00050 X2
042032,000149: 15,3720 77775 DEC -2 B-14
042033,000150: 15,3721 53015 DAD BZE
042034,000151: 15,3722 12026 RCB-13 # PLUS 2
042035,000152: 15,3723 33753 POSITE # 2ND
042036,000153: 15,3724 77644 BPL
042037,000154: 15,3725 33663 POSITA # 1ST
042038,000155: 15,3726 45345 POSITF DLOAD DSU # 3RD
042039,000156: 15,3727 00021 STMP # LOM
042040,000157: 15,3730 00025 STMP +4 # LON
042041,000158: 15,3731 65356 SIN PDDL # SIN(LOM-LON)
042042,000159: 15,3732 00021 STMP
042043,000160: 15,3733 65356 SIN PDDL # SIN LOM
042044,000161: 15,3734 00021 STMP
042045,000162: 15,3735 55546 COS VDEF # COS LOM
042046,000163: 15,3736 53521 MXV UNIT
042047,000164: 15,3737 12002 KONMAT # K1,K2,K3,K4,
042048,000165: 15,3740 02723 STORE VMOON
042049,000166: 15,3741 65345 DLOAD PDDL
042050,000167: 15,3742 12004 KONMAT +2 # ZERO
042051,000168: 15,3743 00023 STMP +2
042052,000169: 15,3744 65356 SIN PDDL # SIN LOS
042053,000170: 15,3745 00023 STMP +2
042054,000171: 15,3746 55546 COS VDEF # COS LOS
042055,000172: 15,3747 53521 MXV UNIT
042056,000173: 15,3750 12002 KONMAT
042057,000174: 15,3751 02715 STORE VSUN
042058,000175: 15,3752 77616 RVQ
|
|
Page 981 |
042060,000177: 15,3753 77745 POSITE DLOAD
042061,000178: 15,3754 12004 KONMAT +2 # ZEROS
042062,000179: 15,3755 00027 STORE GTMP
042063,000180: 15,3756 77650 GOTO
042064,000181: 15,3757 33705 POSITD
042065,000182: 05,2000 SETLOC EPHEM1
042066,000183: 05,2000 BANK
042067,000184:
042068,000185: 05,3505 COUNT* $$/EPHEM
042069,000186: 05,3505 STMP EQUALS 16D
042070,000187: 05,3505 GTMP EQUALS 22D
042071,000188: 05,3505 TIMEP EQUALS 24D
042072,000189:
End of include-file LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc. Parent file is MAIN.agc