GROUND TRACKING DETERMINATION PROGRAM

Scanned pages: 654-657

GROUND_TRACKING_DETERMINATION_PROGRAM.agc

# Copyright:  Public domain.
# Filename:  GROUND_TRACKING_DETERMINATION_PROGRAM.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:  654-657
# Mod history:  2009-05-18 RSB  Adapted from the corresponding
#        Luminary131 file, using page
#        images from Luminary 1A.
#
# 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 654
# GROUND TRACKING DETERMINATION PROGRAM P21
# PROGRAM DESCRIPTION
# MOD NO - 1
# MOD BY - N.M.NEVILLE
# FUNCTIONAL DECRIPTION-
#
# TO PROVIDE THE ASTRONAUT DETAILS OF THE LM OR CSM GROUND TRACK WITHOUT
# THE NEED FOR GROUND COMMUNICATION (REQUESTED BY DSKY).
# CALLING SEQUENCE -
#
# ASTRONAUT REQUEST THROUGH DSKY V37E21E
# SUBROUTINES CALLED-
#
# GOPERF4
# GOFLASH
# THISPREC
# OTHPREC
# LAT-LONG
# NORMAL EXIT MODES-
#
# ASTRONAUT REQUEST TROUGH DSKY TO TERMINATE PROGRAM V34E
# ALARM OR ABORT EXIT MODES-
#
# NONE
# OUTPUT -
#
# OCTAL DISPLAY OF OPTION CODE AND VEHICLE WHOSE GROUND TRACK IS TO BE
# COMPUTED
#  OPTION CODE  00002
#  THIS    00001
#  OTHER    00002
# DECIMAL DISPLAY OF TIME TO BE INTEGRATED TO HOURS , MINUTES , SECONDS
# DECIMAL DISPLAY OF LAT,LONG,ALT
# ERASABLE INITIALIZATION REQUIRED
#
# AXO    2DEC  4.652459653 E-5    RADIANS    %68-69 CONSTANTS"
#
# -AYO    2DEC  2.147535898 E-5    RADIANS
#
# AZO    2DEC  .7753206164    REVOLUTIONS
# FOR LUNAR ORBITS 504LM VECTOR IS NEEDED
#
# 504LM    2DEC  -2.700340600 E-5  RADIANS
#
# 504LM  _2  2DEC  -7.514128400 E-4  RADIANS
#
# 504LM  _4  2DEC  _2.553198641 E-4  RADIANS
#
# NONE
# DEBRIS
#
# Page 655
# CENTRALS-A,Q,L
# OTHER-THOSE USED BY THE ABOVE LISTED SUBROUTINES
# SEE LEMPREC,LAT-LONG
    SBANK=  LOWSUPER  # FOR LOW 2CADR'S.

    BANK  33
    SETLOC  P20S
    BANK

    EBANK=  P21TIME
    COUNT*  $$/P21
PROG21    CAF  ONE
    TS  OPTION2    # ASSUMED VEHICLE IS LM , R2 = 00001
    CAF  BIT2    #  OPTION 2
    TC  BANKCALL
    CADR  GOPERF4
    TC  GOTOPOOH  # TERMINATE
    TC  +2    # PROCEED VALUE OF ASSUMED VEHICLE OK
    TC  -5    # R2 LOADED THROUGH DSKY
P21PROG1  CAF  V6N34    # LOAD DESIRED TIME OF LAT-LONG.
    TC  BANKCALL
    CADR  GOFLASH
    TC  GOTOPOOH  # TERM
    TC  +2    # PROCEED VALUES OK
    TC  -5    # TIME LOADED THROUGH DSKY
    TC  INTPRET
    DLOAD
      DSPTEM1
    STCALL  TDEC1    # INTEGRATE TO TIME SPECIFIED IN TDEC
      INTSTALL
    BON  CLEAR
      P21FLAG
      P21CONT    # ON---RECYCLE USING BASE VECTOR
      VINTFLAG  # OFF--IST PASS CALL BASE VECTOR
    SLOAD  SR1
      OPTION2
    BHIZ  SET
      +2    # ZERO--THIS VEHICLE(LM)
      VINTFLAG  # ONE--OTHER VEHICLE(CM)
    CLEAR  CLEAR
      DIM0FLAG
      INTYPFLG  # PRECISION
    CALL
      INTEGRV    # CALCULATE
    GOTO      # -AND
      P21VSAVE  # -SAVE BASE VECTOR
P21CONT    VLOAD
      P21BASER  # RECYCLE--INTEG FROM BASE VECTOR
    STOVL  RCV    # --POS
# Page 656
      P21BASEV
    STODL  VCV    # --VEL
      P21TIME
    STORE  TET    # --TIME
    CLEAR  CLEAR
      DIM0FLAG
      MOONFLAG
    SLOAD  BZE
      P21ORIG
      +3    # ZERO=EARTH
    SET      # ---2=MOON
      MOONFLAG
 +3    CALL
      INTEGRVS
P21VSAVE  DLOAD      # SAVE CURRENT BASEVECTOR
      TAT
    STOVL  P21TIME    # --TIME
      RATT1
    STOVL  P21BASER  # --POS B-29 OR B-27
      VATT1
    STORE  P21BASEV  # --VEL B-07 OR B-05
    ABVAL  SL*
      0,2
    STOVL  P21VEL    # VEL/ FOR N91 DISP
      RATT
    UNIT  DOT
      VATT    #  U(R).V
    DDV  ASIN    # U(R).U(V)
      P21VEL
    STORE  P21GAM    # SIN-1 U(R).U(V) , -90 TO &90
    SXA,2  SLOAD
      P21ORIG    # 0=EARTH
      OPTION2
    SR1  BHIZ
      +3
    GOTO
      +4
 +3    BON
      SURFFLAG
      P21DSP
 +4    SET
      P21FLAG
P21DSP    CLEAR  SLOAD    # GENERATE DISPLAY DATA
      LUNAFLAG
      X2
    BZE  SET
      +2    # 0 = EARTH
      LUNAFLAG
    VLOAD
      RATT
# Page 657
    STODL  ALPHAV
      TAT
    CLEAR  CALL
      ERADFLAG
      LAT-LONG
    DMP      # MPAC = ALT, METERS B-29
      K.01
    STORE  P21ALT    # ALT/100 FOR N91 DISP
    EXIT
    CAF  V06N43    # DISPLAY LAT, LONG, ALT
    TC  BANKCALL  # LAT, LONG = 1/2 REVS B0
    CADR  GOFLASH    # ALT = KM B14
    TC  GOTOPOOH  # TERM
    TC  GOTOPOOH
    TC  INTPRET    # V32E RECYCLE
    DLOAD  DAD
      P21TIME
      600SEC    # 600 SECONDS OR 10 MIN
    STORE  DSPTEM1
    RTB
      P21PROG1
600SEC    2DEC  60000    # 10 MIN

V06N43    VN  00643
V6N34    VN  00634
K.01    2DEC  .01