S-BAND_ANTENNA_FOR_LM.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: S-BAND_ANTENNA_FOR_LM.agc
## Purpose: A section of Luminary revision 116.
## It is part of the source code for the Lunar Module's (LM)
## Apollo Guidance Computer (AGC) for Apollo 12.
## This file is intended to be a faithful transcription, except
## that the code format has been changed to conform to the
## requirements of the yaYUL assembler rather than the
## original YUL assembler.
## Reference: pp. 488-491
## Assembler: yaYUL
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 2017-01-22 MAS Created from Luminary 99.
## 2017-03-09 RSB Transcribed, and then proofed comment-text using
## 3-way diff vs Luminary 99 and Luminary 131.
## (Admittedly, the former is more for detecting errors
## in Luminary 99 than the other way around.)
## 2017-03-13 HG Remove operand modifier SBANDANT +2 --> SBANDANT
## Page 488
# SUBROUTINE NAME: R05 - S-BAND ANTENNA FOR LM
# MOD0 BY T. JAMES
# MOD1 BY P. SHAKIR
# FUNCTIONAL DESCRIPTION
# THE S-BAND ANTENNA ROUTINE, R05, COMPUTES AND DISPLAYS THE PITCH AND
# YAW ANTENNA GIMBAL ANGLES REQUIRED TO POINT THE LM STEERABLE ANTENNA
# TOWARD THE CENTER OF THE EARTH. THIS ROUTINE IS SELECTED BY THE ASTRO-
# NAUT VIA DSKY ENTRY DURING COASTING FLIGHT OR WHEN THE LM IS ON THE MOON
# SURFACE. THE EARTH OR MOON REFERENCE COORDINATE SYSTEM IS USED DEPENDING
# ON WHETHER THE LM IS ABOUT TO ENTER OR HAS ALREADY ENTERED THE MOON
# SPHERE OF INFLUENCE, RESPECTIVELY. CAN BE CALLED ANY TIME EXCEPT WHEN
# ANOTHER EXTENDED VERB IS IN USE. DISPLAY IS MEANINGLESS WITH IMU OFF.
# TO CALL SUBROUTINE, ASTRONAUT KEYS IN V 64 E
# SUBROUTINES CALLED -
# INTPRET
# LOADTIME
# LEMCONIC
# LUNPOS
# CDUTRIG
# *SMNB*
# BANKCALL
# B5OFF
# ENDOFJOB
# BLANKET
# RETURNS WITH
# PITCH ANGLE IN PITCHANG REV. B0
# YAW ANGLE IN YAWANG REV. B0
# ERASABLES USED
# PITCHANG
# YAWANG
# RLM
# VAC AREA
BANK 41
SETLOC SBAND
BANK
EBANK= WHOCARES
COUNT* $$/R05
SBANDANT TC INTPRET
## Page 489
SETPD RTB
0D
LOADTIME # PICK UP CURRENT TIME
STCALL TDEC1 # ADVANCE INTEGRATION TO TIME IN TDEC1
LEMCONIC # USING CONIC INTEGRATION
SLOAD BHIZ
X2 # X2 =0 EARTH SPHERE, X2 =2 MOON SPHERE
CONV4
VLOAD
RATT
STODL RLM
TAT
CONV3 CALL
LUNPOS # UNIT POSITION VECTOR FROM EARTH TO MOON
VLOAD VXSC
VMOON
REMDIST # MEAN DISTANCE FROM EARTH TO MOON
VSL1 VAD
RLM
GOTO
CONV5
CONV4 VLOAD
RATT # UE = -UNIT(RATT) EARTH SPHERE
CONV5 SETPD UNIT # UE = -UNIT((REM)(UEM) + RL) MOON SPHERE
0D # SET PL POINTER TO 0
VCOMP CALL
CDUTRIG # COMPUTE SINES AND COSINES OF CDU ANGLES
MXV VSL1 # TRANSFORM REF. COORDINATE SYSTEM TO
REFSMMAT # STABLE MEMBER B-1 X B-1 X B+1 = B-1
PUSH DLOAD # 8D
HI6ZEROS
STORE PITCHANG
STOVL YAWANG # ZERO OUT ANGLES
CALL
*SMNB*
STODL RLM # PRE-MULTIPLY RLM BY (NBSA) MATRIX(B0)
RLM +2
PUSH DSU
RLM
DMP
1OVSQRT2
STODL RLM +2
DAD DMP
RLM
1OVSQRT2
STOVL RLM # R B-1
RLM
UNIT PDVL
RLM
VPROJ VSL2 # PROJECTION OF R ONTO LM XZ PLANE
## Page 490
HIUNITY
BVSU BOV # CLEAR OVERFLOW INDICATOR IF ON
RLM
COVCNV
COVCNV UNIT BOV # EXIT ON OVERFLOW
SBANDEX
PUSH VXV # URP VECTOR B-1
HIUNITZ
VSL1 VCOMP # UZ X URP = -(URP X UZ)
STORE RLM # X VEC B-1
DOT PDVL # SGN(X.UY) UNSCALED
HIUNITY
RLM
ABVAL SIGN
ASIN # ASIN((SGN(X.UY))ABV(X)) REV B0
STOVL PITCHANG
URP
DOT BPL
HIUNITZ
NOADJUST # YES, -90 TO +90
DLOAD DSU
HIDPHALF
PITCHANG
STORE PITCHANG
NOADJUST VLOAD VXV
UR # Z = (UR X URP)
URP
VSL1
STODL RLM # Z VEC B-1
PITCHANG
SIN VXSC
HIUNITZ
PDDL COS
PITCHANG
VXSC VSU
HIUNITX # (UX COS ALPHA) - (UZ SIN ALPHA)
DOT PDVL # YAW.Z
RLM
RLM
ABVAL SIGN
ASIN
STORE YAWANG
SBANDEX EXIT
CA EXTVBACT
MASK BIT5 # IS BIT5 STILL ON
EXTEND
BZF ENDEXT # NO
CAF PRIO5
TC PRIOCHNG
CAF V06N51 # DISPLAY ANGLES
## Page 491
TC BANKCALL
CADR GOMARKFR
TC B5OFF # TERMINATE
TC B5OFF # PROCEED
TC ENDOFJOB # RECYCLE
CAF BIT3 # IMMEDIATE RETURN
TC BLANKET # BLANK R3
CAF PRIO4
TC PRIOCHNG
TC SBANDANT # YES, CONTINUE DISPLAYING ANGLES.
V06N51 VN 0651
1OVSQRT2 2DEC .7071067815 # 1/SQRT(2)
UR EQUALS 0D
URP EQUALS 6D
SBANK= LOWSUPER
