197 lines
5.9 KiB
Plaintext
197 lines
5.9 KiB
Plaintext
# Copyright: Public domain.
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# Filename: LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc
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# Purpose: Part of the source code for Luminary 1A build 099.
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# It is part of the source code for the Lunar Module's (LM)
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# Apollo Guidance Computer (AGC), for Apollo 11.
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# Assembler: yaYUL
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# Contact: Hartmuth Gutsche <hgutsche@xplornet.com>.
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# Website: www.ibiblio.org/apollo.
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# Pages: 984-987
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# Mod history: 2009-05-24 HG Transcribed from page images.
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#
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# This source code has been transcribed or otherwise adapted from
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# digitized images of a hardcopy from the MIT Museum. The digitization
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# was performed by Paul Fjeld, and arranged for by Deborah Douglas of
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# the Museum. Many thanks to both. The images (with suitable reduction
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# in storage size and consequent reduction in image quality as well) are
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# available online at www.ibiblio.org/apollo. If for some reason you
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# find that the images are illegible, contact me at info@sandroid.org
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# about getting access to the (much) higher-quality images which Paul
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# actually created.
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#
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# Notations on the hardcopy document read, in part:
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#
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# Assemble revision 001 of AGC program LMY99 by NASA 2021112-061
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# 16:27 JULY 14, 1969
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# Page 984
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# NAME -- LSPOS -- LOCATE SUN AND MOON DATE -- 25 OCT 67
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# MOD NO. 1
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# MOD BY NEVILLE ASSEMBLY SUNDANCE
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#
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# FUNCTIONAL DESCRIPTION
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#
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# COMPUTES UNIT POSITION VECTOR OF THE SUN AND MOON IN THE BASIC REFERENCE SYSTEM. THE SUN VECTOR S IS
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# LOCATED VIA TWO ANGLES. THE FIRST ANGLE (OBLIQUITY) IS THE ANGLE BETWEEN THE EARTH EQUATOR AND THE ECLIPTIC. THE
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# POSITION VECTOR OF THE SUN IS
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# _
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# S = (COS(LOS), COS(OBL)*SIN(LOS), SIN(OBL)*SIN(LOS)), WHERE
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#
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# LOS = LOS +LOS *T-(C *SIN(2PI*T)/365.24 +C *COS(2PI*T)/365.24)
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# 0 R 0 1
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# LOS (RAD) IS THE LONGITUDE OF THE SUN FOR MIGNIGHT JUNE 30TH OF THE PARTICULAR YEAR.
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# 0
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# LOS (RAD/DAY) IS THE MEAN RATE FOR THE PARTICULAR YEAR.
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# R
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#
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# LOS AND LOS ARE STORED AS LOSC AND LOSR IN RATESP.
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# 0 R
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# COS(OBL) AND SIN(OBL) ARE STORED IN THE MATRIX KONMAT.
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#
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# T, TIME MEASURED IN DAYS (24 HOURS) IS STORED IN TIMEP.
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#
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# C AND C ARE FUDGE FACTORS TO MINIMIZE THE DEVIATION. THEY ARE STORED AS ONE CONSTANT (CMOD), SINCE
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# 0 1 2 2 1/2
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# C *SIN(X)+C *COS(X) CAN BE WRITTEN AS (C +C ) *SIN(X+PHI), WHERE PHI=ARCTAN(C /C ).
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# 0 1 1 0
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#
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# THE MOON IS LOCATED VIA FOUR ANGLES, THE FIRST IS THE OBLIQUITY. THE SECOND IS THE MEAN LONGITUDE OF THE MOON,
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# MEASURED IN THE ECLIPTIC FROM THE MEAN EQUINOX TO THE MEAN ASCENDING NODE OF THE LUNAR ORBIT, AND THEN ALONG THE
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# ORBIT. THE THIRD ANGLE IS THE ANGLE BETWEEN THE ECLIPTIC AND THE LUNAR ORBIT. THE FOURTH ANGLE IS THE LONGITUDE
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# OF THE NODE OF THE MOON, MEASURED IN THE LUNAR ORBIT. LET THESE ANGLES BE OBL,LOM,IM, AND LON RESPECTIVELY.
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#
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# THE SIMPLIFIED POSITION VECTOR OF THE MOON IS
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# _
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# 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))
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#
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# WHERE
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# 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
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# 0 R 0 1 0 1
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# LON=LON +LON
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# 0 R
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# A , A , B AND B ARE STORE AS AMOD AND BMOD (SEE DESCRIPTION OF CMOD, ABOVE). COS(OBL), SIN(OBL)*SIN(IM),
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# 0 1 0 1
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# SIN(OBL), AND COS(OBL)*SIN(IM) ARE STORED IN KONMAT AS K1, K2, K3, AND K4, RESPECTIVELY. LOM , LOM , LON , LON
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# 0 R 0 R
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# ARE STORED AS LOM0, LOMR, LON0, AND LONR IN RATESP.
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#
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# THE THREE PHIS ARE STORED AS AARG, BARG, AND CARG(SUN). ALL CONSTANTS ARE UPDATED BY YEAR.
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#
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# CALLING SEQUENCE
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# Page 985
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# CALL LSPOS. RETURN IS VIA CPRET.
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#
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# ALARMS OR ABORTS
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# NONE
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#
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# ERASABLE INITIALIZATION REQUIRED
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# TEPHEM -- TIME FROM MIGNIGHT 1 JULY PRECEDING THE LAUNCH TO THE TIME OF THE LAUNCH (WHEN THE AGC CLOCK WENT
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# TO ZERO). TEPHEM IS TP WITH UNITS OF CENTI-SECONDS.
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#
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# TIME2 AND TIME1 ARE IN MPAC AND MPAC +1 WHEN PROGRAM IS CALLED.
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#
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# OUTPUT
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# UNIT POSITIONAL VECTOR OF SUN IN VSUN. (SCALED B-1)
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# UNIT POSITIONAL VECTOR OF MOON IN VMOON. (SCALED B-1)
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#
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# SUBROUTINES USED
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# NONE
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#
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# DEBRIS
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# CURRENT CORE SET, WORK AREA AND FREEFLAG
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BANK 04
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SETLOC EPHEM
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BANK
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EBANK= VSUN
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COUNT* $$/EPHEM
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LUNPOS EQUALS LSPOS
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LSPOS SETPD SR
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0
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14D # TP
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TAD DDV
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# HG comments in [...] are hand written comments in original listing
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TEPHEM # TIME OF LAUNCH [IN CENTISEC B 42]
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CSTODAY # 24 HOURS -- 8640000 CENTI-SECS/DAY B-33
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STORE TIMEP # T IN DAYS [@ B 9 = 512 DAYS]
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AXT,1 AXT,2 # [GRANULRITY = 0.164 SEC]
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0
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0
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CLEAR
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FREEFLAG # SWITCH BIT
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POSITA DLOAD
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KONMAT +2 # ZEROS
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STORE GTMP
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POSITB DLOAD DMP*
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TIMEP # T
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VAL67 +4,1 # 1/27 OR 1/32 OR 1/365
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# Page 986
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SL DAD*
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8D
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VAL67 +2,1 # AARG
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SIN DMP* # SIN(T/27+PHI) OR T/32 OR T/365
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VAL67,1 # (A0**2+A1**2)**1/2 SIN(X+PHIA)
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DAD INCR,1 # PLUS
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GTMP # (B0**2+B1**2)**1/2 SIN(X+PHIB)
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DEC -6
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STORE GTMP # OR (C0**2+C1**2)**1/2 SIN(X+PHIC)
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BOFSET
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FREEFLAG
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POSITB
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POSITD DLOAD DMP*
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TIMEP # T
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RATESP,2 # LOMR,LOSR,LONR
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SL DAD*
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5D
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RATESP +6,2 # LOM0,LOS0,LON0
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DSU
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GTMP
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STORE STMP,2 # LOM,LOS,LON
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SLOAD INCR,2
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X2
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DEC -2
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DAD BZE
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RCB-13 # PLUS 2
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POSITE # 2ND
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BPL
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POSITA # 1ST
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POSITF DLOAD DSU # 3RD
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STMP # LOM
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STMP +4 # LON
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SIN PDDL # SIN(LOM-LON)
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STMP
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SIN PDDL # SIN LOM
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STMP
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COS VDEF # COS LOM
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MXV UNIT
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KONMAT # K1,K2,K3,K4,
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STORE VMOON
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DLOAD PDDL
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KONMAT +2 # ZERO
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STMP +2
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SIN PDDL # SIN LOS
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STMP +2
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COS VDEF # COS LOS
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MXV UNIT
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KONMAT
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STORE VSUN
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RVQ
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# Page 987
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POSITE DLOAD
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KONMAT +2 # ZEROS
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STORE GTMP
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GOTO
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POSITD
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LUNVEL RVQ
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SETLOC EPHEM1
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BANK
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COUNT* $$/EPHEM
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STMP EQUALS 16D
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GTMP EQUALS 22D
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TIMEP EQUALS 24D
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# *** END OF LEMP50S .115 ***
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