S BAND ANTENNA FOR LM

Scanned pages: 486-489

S-BAND_ANTENNA_FOR_LM.agc

# Copyright:  Public domain.
# Filename:  S-BAND_ANTENNA_FOR_LM.agc
# Purpose:   Part of the source code for Luminary 1A build 099.
#    It is part of the source code for the Lunar Module's (LM)
#    Apollo Guidance Computer (AGC), for Apollo 11.
# Assembler:  yaYUL
# Contact:  Ron Burkey <info@sandroid.org>.
# Website:  www.ibiblio.org/apollo.
# Pages:  486-489
# Mod history:  2009-05-17 RSB  Adapted from the corresponding
#        Luminary131 file, using page
#        images from Luminary 1A.
#    2009-06-07 RSB  Corrected a misprint.
#
# This source code has been transcribed or otherwise adapted from
# digitized images of a hardcopy from the MIT Museum.  The digitization
# was performed by Paul Fjeld, and arranged for by Deborah Douglas of
# the Museum.  Many thanks to both.  The images (with suitable reduction
# in storage size and consequent reduction in image quality as well) are
# available online at www.ibiblio.org/apollo.  If for some reason you
# find that the images are illegible, contact me at info@sandroid.org
# about getting access to the (much) higher-quality images which Paul
# actually created.
#
# Notations on the hardcopy document read, in part:
#
#  Assemble revision 001 of AGC program LMY99 by NASA 2021112-061
#  16:27 JULY 14, 1969

# Page 486
# 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
#
# TO CALL SUBROUTINE, ASTRONAUT KEYS IN V 64 E
#
# SUBROUTINES CALLED-
#  R02BOTH
#  INTPRET
#  LOADTIME
#  LEMCONIC
#  LUNPOS
#  CDUTRIG
#  *SMNB*
#  BANKCALL
#  B50OFF
#  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  BANKCALL
# Page 487
    CADR  R02BOTH    # CHECK IF IMU IS ON AND ALIGNED
    TC  INTPRET
    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
# Page 488
      RLM
    VPROJ  VSL2    # PROJECTION OF R ONTO LM XZ PLANE
      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
# Page 489
    TC  PRIOCHNG
    CAF  V06N51    # DISPLAY ANGLES
    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 +2  # YES, CONTINUE DISPLAYING ANGLES
V06N51    VN  0651
1OVSQRT2  2DEC  .7071067815  # 1/SQRT(2)

UR    EQUALS  0D
URP    EQUALS  6D
    SBANK=  LOWSUPER

# *** END OF LNYAIDE .001 ***