Source Code

041360,000001: # Copyright: Public domain. 041361,000002: # Filename: LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc 041362,000003: # Purpose: A section of Luminary 1C, revision 131. 041363,000004: # It is part of the source code for the Lunar Module's (LM) 041364,000005: # Apollo Guidance Computer (AGC) for Apollo 13 and Apollo 14. 041365,000006: # This file is intended to be a faithful transcription, except 041366,000007: # that the code format has been changed to conform to the 041367,000008: # requirements of the yaYUL assembler rather than the 041368,000009: # original YUL assembler. 041369,000010: # Reference: pp. 983-986 of 1729.pdf. 041370,000011: # Contact: Ron Burkey <info@sandroid.org>. 041371,000012: # Website: www.ibiblio.org/apollo/index.html 041372,000013: # Mod history: 05/29/03 RSB. Began transcribing. 041373,000014: # 05/14/05 RSB Corrected website reference above. 041374,000015: 041375,000016: # Page 983 041376,000017: # NAME -- LSPOS -- LOCATE SUN AND MOON DATE -- 25 OCT 67 041377,000018: # MOD NO. 1 041378,000019: # MOD BY NEVILLE ASSEMBLY SUNDANCE 041379,000020: 041380,000021: # FUNCTIONAL DESCRIPTION 041381,000022: 041382,000023: # COMPUTES UNIT POSITION VECTOR OF THE SUN AND MOON IN THE BASIC REFERENCE SYSTEM. THE SUN VECTOR S IS 041383,000024: # LOCATED VIA TWO ANLES. THE FIRST ANGLE (OBLIQUITY) IS THE ANGLE BETWEEN THE EARTH EQUATOR AND THE ECLIPTIC. THE 041384,000025: # POSITION VECTOR OF THE SUN IS 041385,000026: # _ 041386,000027: # S = (COS(LOS), COS(OBL)*SIN(LOS), SIN(OBL)*SIN(LOS)), WHERE 041387,000028: 041388,000029: # LOS = LOS +LOS *T-(C *SIN(2PI*T)/365.24 +C *COS(2PI*T)/365.24) 041389,000030: # 0 R 0 1 041390,000031: # LOS (RAD) IS THE LONGITUDE OF THE SUN FOR MIGNIGHT JUNE 30TH OF THE PARTICULAR YEAR. 041391,000032: # 0 041392,000033: # LOS (RAD/DAY) IS THE MEAN RATE FOR THE PARTICULAR YEAR. 041393,000034: # R 041394,000035: 041395,000036: # LOS AND LOS ARE STORED AS LOSC AND LOSR IN RATESP. 041396,000037: # 0 R 041397,000038: # COS(OBL) AND SIN(OBL) ARE STORED IN THE MATRIX KONMAT. 041398,000039: 041399,000040: # T, TIME MEASURED IN DAYS (24 HOURS) IS STORED IN TIMEP. 041400,000041: 041401,000042: # C AND C ARE FUDGE FACTORS TO MINIMIZE THE DEVIATION. THEY ARE STORED AS ONE CONSTANT (CMOD), SINCE 041402,000043: # 0 1 2 2 1/2 041403,000044: # C *SIN(X)+C *COS(X) CAN BE WRITTEN AS (C +C ) *SIN(X+PHI), WHERE PHI=ARCTAN(C /C ). 041404,000045: # 0 1 1 0 041405,000046: 041406,000047: # THE MOON IS LOCATED VIA FOUR ANGLES, THE FIRST IS THE OBLIQUITY. THE SECOND IS THE MEAN LONGITUDE OF THE MOON, 041407,000048: # MEASURED IN THE ECLIPTIC FROM THE MEAN EQUINOX TO THE MEAN ASCENDING NODE OF THE LUNAR ORBIT, AND THEN ALONG THE 041408,000049: # ORBIT. THE THIRD ANGLE IS THE ANGLE BETWEEN THE ECLIPTIC AND THE LUNAR ORBIT. THE FOURTH ANGLE IS THE LONGITUDE 041409,000050: # OF THE NODE OF THE MOON, MEASURED IN THE LUNAR ORBIT. LET THESE ANGLES BE OBL,LOM,IM, AND LON RESPECTIVELY. 041410,000051: 041411,000052: # THE SIMPLIFIED POSITION VECTOR OF THE MOON IS 041412,000053: # _ 041413,000054: # 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)) 041414,000055: 041415,000056: # WHERE 041416,000057: # 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 041417,000058: # 0 R 0 1 0 1 041418,000059: # LON=LON +LON 041419,000060: # 0 R 041420,000061: # A , A , B AND B ARE STORE AS AMOD AND BMOD (SEE DESCRIPTION OF CMOD, ABOVE). COS(OBL), SIN(OBL)*SIN(IM), 041421,000062: # 0 1 0 1 041422,000063: # SIN(OBL), AND COS(OBL)*SIN(IM) ARE STORED IN KONMAT AS K1, K2, K3, AND K4, RESPECTIVELY. LOM , LOM , LON , LON 041423,000064: # 0 R 0 R 041424,000065: # ARE STORED AS LOM0, LOMR, LON0, AND LONR IN RATESP. 041425,000066: 041426,000067: # THE THREE PHIS ARE STORED AS AARG, BARG, AND CARG(SUN). ALL CONSTANTS ARE UPDATED BY YEAR. 041427,000068: 041428,000069: # CALLING SEQUENCE 041429,000070: # Page 984 041430,000071: # CALL LSPOS. RETURN IS VIA CPRET. 041431,000072: 041432,000073: # ALARMS OR ABORTS 041433,000074: # NONE 041434,000075: 041435,000076: # ERASABLE INITIALIZATION REQUIRED 041436,000077: # TEPHEM -- TIME FROM MIGNIGHT 1 JULY PRECEDING THE LAUNCH TO THE TIME OF THE LAUNCH (WHEN THE AGC CLOCK WENT 041437,000078: # TO ZERO). TEPHEM IS TP WITH UNITS OF CENTI-SECONDS. 041438,000079: 041439,000080: # TIME2 AND TIME1 ARE IN MPAC AND MPAC +1 WHEN PROGRAM IS CALLED. 041440,000081: 041441,000082: # OUTPUT 041442,000083: # UNIT POSITIONAL VECTOR OF SUN IN VSUN. (SCALED B-1) 041443,000084: # UNIT POSITIONAL VECTOR OF MOON IN VMOON. (SCALED B-1) 041444,000085: 041445,000086: # SUBROUTINES USED 041446,000087: # NONE 041447,000088: 041448,000089: # DEBRIS 041449,000090: # CURRENT CORE SET, WORK AREA AND FREEFLAG 041450,000091: 041451,000092: 04,2773 BANK 04 041452,000093: 15,2000 SETLOC EPHEM 041453,000094: 15,2000 BANK 041454,000095: 041455,000096: 15,3647 E5,1714 EBANK= VSUN 041456,000097: 15,3647 COUNT* $$/EPHEM 041457,000098: 15,3647 15,3647 LUNPOS EQUALS LSPOS 041458,000099: 041459,000100: 15,3647 54201 LSPOS SETPD SR 041460,000101: 15,3650 00001 0 041461,000102: 15,3651 20617 14D # TP 041462,000103: 15,3652 56371 TAD DDV 041463,000104: 15,3653 01707 TEPHEM # TIME OF LAUNCH 041464,000105: 15,3654 12024 CSTODAY # 24 HOURS -- 8640000 CENTI-SECS/DAY B-33 041465,000106: 15,3655 00031 STORE TIMEP # T IN DAYS 041466,000107: 15,3656 77170 AXT,1 AXT,2 041467,000108: 15,3657 00000 0 041468,000109: 15,3660 00000 0 041469,000110: 15,3661 77614 CLEAR 041470,000111: 15,3662 00274 FREEFLAG # SWITCH BIT 041471,000112: 15,3663 77745 POSITA DLOAD 041472,000113: 15,3664 12004 KONMAT +2 # ZEROS 041473,000114: 15,3665 00027 STORE GTMP 041474,000115: 15,3666 40745 POSITB DLOAD DMP* 041475,000116: 15,3667 00031 TIMEP # T 041476,000117: 15,3670 12050 VAL67 +4,1 # 1/27 OR 1/32 OR 1/365 041477,000118: # Page 985 041478,000119: 15,3671 42661 SL DAD* 041479,000120: 15,3672 20211 8D 041480,000121: 15,3673 12046 VAL67 +2,1 # AARG 041481,000122: 15,3674 40756 SIN DMP* # SIN(T/27+PHI) OR T/32 OR T/365 041482,000123: 15,3675 12044 VAL67,1 # (A0**2+A1**2)**1/2 SIN(X+PHIA) 041483,000124: 15,3676 62015 DAD INCR,1 # PLUS 041484,000125: 15,3677 00027 GTMP # (B0**2+B1**2)**1/2 SIN(X+PHIB) 041485,000126: 15,3700 77771 DEC -6 B-14 041486,000127: 15,3701 00027 STORE GTMP # OR (C0**2+C1**2)**1/2 SIN(X+PHIC) 041487,000128: 15,3702 77614 BOFSET 041488,000129: 15,3703 00054 FREEFLAG 041489,000130: 15,3704 33666 POSITB 041490,000131: 15,3705 40745 POSITD DLOAD DMP* 041491,000132: 15,3706 00031 TIMEP # T 041492,000133: 15,3707 65747 RATESP,2 # LOMR,LOSR,LONR 041493,000134: 15,3710 42661 SL DAD* 041494,000135: 15,3711 20206 5D 041495,000136: 15,3712 65741 RATESP +6,2 # LOM0,LOS0,LON0 041496,000137: 15,3713 77625 DSU 041497,000138: 15,3714 00027 GTMP 041498,000139: 15,3715 10021 STORE STMP,2 # LOM,LOS,LON 041499,000140: 15,3716 63135 SLOAD INCR,2 041500,000141: 15,3717 00050 X2 041501,000142: 15,3720 77775 DEC -2 B-14 041502,000143: 15,3721 53015 DAD BZE 041503,000144: 15,3722 12026 RCB-13 # PLUS 2 041504,000145: 15,3723 33753 POSITE # 2ND 041505,000146: 15,3724 77644 BPL 041506,000147: 15,3725 33663 POSITA # 1ST 041507,000148: 15,3726 45345 POSITF DLOAD DSU # 3RD 041508,000149: 15,3727 00021 STMP # LOM 041509,000150: 15,3730 00025 STMP +4 # LON 041510,000151: 15,3731 65356 SIN PDDL # SIN(LOM-LON) 041511,000152: 15,3732 00021 STMP 041512,000153: 15,3733 65356 SIN PDDL # SIN LOM 041513,000154: 15,3734 00021 STMP 041514,000155: 15,3735 55546 COS VDEF # COS LOM 041515,000156: 15,3736 53521 MXV UNIT 041516,000157: 15,3737 12002 KONMAT # K1,K2,K3,K4 041517,000158: 15,3740 02723 STORE VMOON 041518,000159: 15,3741 65345 DLOAD PDDL 041519,000160: 15,3742 12004 KONMAT +2 # ZERO 041520,000161: 15,3743 00023 STMP +2 041521,000162: 15,3744 65356 SIN PDDL # SIN LOS 041522,000163: 15,3745 00023 STMP +2 041523,000164: 15,3746 55546 COS VDEF # COS LOS 041524,000165: 15,3747 53521 MXV UNIT 041525,000166: 15,3750 12002 KONMAT 041526,000167: 15,3751 02715 STORE VSUN 041527,000168: 15,3752 77616 RVQ 041528,000169: # Page 986 041529,000170: 15,3753 77745 POSITE DLOAD 041530,000171: 15,3754 12004 KONMAT +2 # ZEROS 041531,000172: 15,3755 00027 STORE GTMP 041532,000173: 15,3756 77650 GOTO 041533,000174: 15,3757 33705 POSITD 041534,000175: 05,2000 SETLOC EPHEM1 041535,000176: 05,2000 BANK 041536,000177: 041537,000178: 05,3505 COUNT* $$/EPHEM 041538,000179: 05,3505 STMP EQUALS 16D 041539,000180: 05,3505 GTMP EQUALS 22D 041540,000181: 05,3505 TIMEP EQUALS 24D 041541,000182: 041542,000183: # *** END OF LEMP50S .119 *** End of include-file LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc. Parent file is MAIN.agc