### FILE="Main.annotation"
## Copyright:   Public domain.
## Filename:	LUNAR_AND_SOLAR_EPHEMERIDES_SUBROUTINES.agc
## Purpose:     Part of the source code for Colossus build 237.
##              This is for the Command Module's (CM) Apollo Guidance
##              Computer (AGC), for Apollo 8.
## Assembler:   yaYUL
## Contact:     Jim Lawton <jim DOT lawton AT gmail DOT com>
## Website:     www.ibiblio.org/apollo/index.html
## Page Scans:  www.ibiblio.org/apollo/ScansForConversion/Colossus237/
## Mod history: 2011-02-27 JL	Adapted from corresponding Colossus 249 file.
##		2016-12-31 RSB	Proofed comment text using octopus/ProoferComments,
##				and corrected errors found.

## Page 736
# LUNAR AND SOLAR EPHEMERIDES SUBROUTINES

# FUNCTIONAL DESCRIPTION

#       THESE SUBROUTINES ARE USED TO DETERMINE THE POSITION AND VELOCITY
#       VECTORS OF THE SUN AND THE MOON RELATIVE TO THE EARTH AT THE
#       SPECIFIED GROUND ELAPSED TIME INPUT BY THE USER.

#       THE POSITION OF THE MOON IS STORED IN THE COMPUTER IN THE FORM OF
#       A NINTH DEGREE POLYNOMIAL APPROXIMATION WHICH IS VALID OVER A 15
#       DAY INTERVAL BEGINNING SHORTLY BEFORE LAUNCH.  THEREFORE THE TIME
#       INPUT BY THE USER SHOULD FALL WITHIN THIS 15 DAY INTERVAL.

#       LSPOS COMPUTES THE POSITION VECTORS OF THE SUN AND THE MOON.

#       LUNPOS COMPUTES THE POSITION VECTOR OF THE MOON.

#       LUNVEL COMPUTES THE VELOCITY VECTOR OF THE MOON.

#       SOLPOS COMPUTES THE POSITION VECTOR OF THE SUN.

# CALLING SEQUENCE

#       DLOAD  CALL
#              TIME               GROUND ELAPSED TIME
#              SUBROUTINE         LSPOS OR LUNPOS OR LUNVEL OR SOLPOS

# INPUT

#       1) SPECIFIED GROUND ELAPSED TIME IN CS X B-28 LOADED IN MPAC.

#       2) TIMEMO - TIME AT THE CENTER OF THE RANGE OVER WHICH THE LUNAR
#          POSITION POLYNOMIAL IS VALID IN CS X B-42.

#       3) VECOEM - VECTOR COEFFICIENTS OF THE LUNAR POSITION POLYNOMIAL
#          LOADED IN DESCENDING SEQUENCE IN METERS/CS**N X B-2

#       4) RESO - POSITION VECTOR OF THE SUN RELATIVE TO THE EARTH AT
#          TIMEMO IN METERS X B-38.

#       5) VESO - VELOCITY VECTOR OF THE SUN RELATIVE TO THE EARTH AT
#          TIMEMO IN METERS/CS X B-9.

#       6) OMEGAES - ANGULAR VELOCITY OF THE VECTOR RESO AT TIMEMO IN
#          REV/CS X B+26.

#       ALL EXCEPT THE FIRST INPUT ARE INCLUDED IN THE PRE-LAUNCH
#       ERASABLE DATA LOAD.

# OUTPUT - LSPOS
## Page 737
#       1) 2D OF VAC AREA CONTAINS THE POSITION VECTOR OF THE SUN RELATIVE
#          TO THE EARTH AT TIME INPUT BY THE USER IN METERS X B-38.

#       2) MPAC CONTAINS THE POSITION VECTOR OF THE MOON RELATIVE TO THE
#          EARTH AT TIME INPUT BY THE USER IN METERS X B-29.

# OUTPUT - LUNPOS

#       MPAC CONTAINS THE POSITION VECTOR OF THE MOON RELATIVE TO THE
#       EARTH AT THE TIME INPUT BY USER IN METERS X B-29.

# OUTPUT - LUNVEL

#       MPAC CONTAINS THE VELOCITY VECTOR OF THE MOON RELATIVE TO THE
#       EARTH AT TIME INPUT BY THE USER IN METERS/CS X B-7.

# OUTPUT - SOLPOS

#       MPAC CONTAINS THE POSITION VECTOR OF THE SUN RELATIVE TO THE EARTH
#       AT TIME INPUT BY THE USER IN METERS X B-38.

# SUBROUTINES USED

#       NONE

# REMARKS

#       THE VAC AREA IS USED FOR STORAGE OF INTERMEDIATE AND FINAL RESULTS
#       OF COMPUTATIONS.

#       S1, X1 AND X2 ARE USED BY THESE SUBROUTINES.
#       PRELAUNCH ERASABLE DATA LOAD ARE ONLY ERASABLE STORAGE USED BY
#       THESE SUBROUTINES.
#       RESTARTS DURING OPERATION OF THESE SUBROUTINES MUST BE HANDLED BY
#       THE USER.

		BANK	36
		SETLOC	EPHEM
		BANK

		COUNT*	$$/EPHEM
		EBANK=	END-E7
LSPOS		AXT,2			# COMPUTES POSITION VECTORS OF BOTH THE
			RESA		# SUN AND THE MOON.  THE POSITION VECTOR
		AXT,1	GOTO		# OF THE SUN IS STORED IN 2D OF THE VAC
			RES		# AREA.  THE POSITION VECTOR OF THE MOON
			LSTIME		# IS STORED IN MPAC.
LUNPOS		AXT,1	GOTO		# COMPUTES THE POSITION VECTOR OF THE MOON
			REM		# AND STORES IT IN MPAC.
			LSTIME
## Page 738
LUNVEL		AXT,1	GOTO		# COMPUTES THE VELOCITY VECTOR OF THE MOON
			VEM		# AND STORES IT IN MPAC.
			LSTIME
SOLPOS		STQ	AXT,1		# COMPUTES THE POSITION VECTOR OF THE SUN
			X2		# AND STORES IT IN MPAC.
			RES
LSTIME		SETPD	SR
			0D
			14D
		TAD	DCOMP
			TEPHEM
		TAD	DCOMP
			TIMEMO
		SL	SSP
			16D
			S1
			6D
		GOTO
			X1
RES		PUSH	DMP		#                                    PD- 2
			OMEGAES
		PUSH	COS		#                                    PD- 4
		VXSC	PDDL		#                                    PD- 8
			RESO	
		SIN	PDVL		#                                    PD-10
			RESO
		PUSH	UNIT		#                                    PD-16
		VXV	UNIT
			VESO
		VXV	VSL1		#                                    PD-10
		VXSC	VAD		#                                    PD-02
		VSL1	GOTO		# RES IN METERS X B-38 IN MPAC.
			X2
RESA		STODL	2D		# RES IN METERS X B-38 IN 2D OF VAC. PD- 0
REM		AXT,1	PDVL		#                                    PD- 2
			54D
			VECOEM
REMA		VXSC	VAD*
			0D
			VECOEM +60D,1
		TIX,1	VSL2		# REM IN METERS X B-29 IN MPAC.
			REMA
		RVQ
VEM		AXT,1	PDDL		#                                    PD- 2
			48D
			NINEB4
		PUSH	VXSC		#                                    PD- 4
			VECOEM
VEMA		VXSC
			0D
## Page 739
		STODL	4D		#                                    PD- 2
		DSU	PUSH		#                                    PD- 4
			ONEB4
		VXSC*	VAD
			VECOEM +54D,1
			4D
		TIX,1	VSL2		# VEM IN METERS/CS X B-7 IN MPAC.
			VEMA
		RVQ
NINEB4		2DEC	9.0 B-4
ONEB4		2DEC	1.0 B-4