THE_LUNAR_LANDING.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: THE_LUNAR_LANDING.agc
## Purpose: A section of Luminary 1C, revision 131.
## It is part of the source code for the Lunar Module's (LM)
## Apollo Guidance Computer (AGC) for Apollo 13.
## 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. 780-787
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 05/25/03 RSB. Began transcribing.
## 05/14/05 RSB Corrected website reference above.
## 2017-01-06 RSB Page numbers now agree with those on the
## original hardcopy, as opposed to the PDF page
## numbers in 1701.pdf.
## 2017-02-25 RSB Proofed comment text using octopus/ProoferComments.
## 2017-03-01 RSB Fixed lingering typos.
## 2017-03-14 RSB Comment-text fixes noted in proofing Luminary 116.
## 2017-03-16 RSB Comment-text fixes identified in 5-way
## side-by-side diff of Luminary 69/99/116/131/210.
## Page 780
BANK 32
SETLOC F2DPS*32
BANK
EBANK= E2DPS
# ****************************************
# P63: THE LUNAR LANDING, BRAKING PHASE
# ****************************************
COUNT* $$/P63
P63LM TC PHASCHNG
OCT 04024
TC BANKCALL # DO IMU STATUS CHECK ROUTINE R02
CADR R02BOTH
CAF P63ADRES # INITIALIZE WHICH FOR BURNBABY
TS WHICH
CAF DPSTHRSH # INITIALIZE DVMON
TS DVTHRUSH
CAF FOUR
TS DVCNTR
CS ONE # INITIALIZE WCHPHASE AND FLPASSO
TS WCHPHASE
CA ZERO
TS FLPASS0
CS BIT14
EXTEND
WAND CHAN12 # REMOVE TRACK-ENABLE DISCRETE.
FLAGORGY TC INTPRET # DIONYSIAN FLAG WAVING
CLEAR CLEAR
NOTHROTL
REDFLAG
CLEAR SET
LRBYPASS
MUNFLAG
CLEAR CLEAR
P25FLAG # TERMINATE P25 IF IT IS RUNNING.
RNDVZFLG # TERMINATE P20 IF IT IS RUNNING
# ****************************************
IGNALG SETPD VLOAD # FIRST SET UP INPUTS FOR RP-TO-R:-
## Page 781
0 # AT 0D LANDING SITE IN MOON FIXED FRAME
RLS # AT 6D ESTIMATED TIME OF LANDING
PDDL PUSH # MPAC NON-ZERO TO INDICATE LUNAR CASE
TLAND
STCALL TPIP # ALSO SET TPIP FOR FIRST GUIDANCE PASS
RP-TO-R
VSL4 MXV
REFSMMAT
STCALL LAND
GUIDINIT # GUIDINIT INITIALIZES WM AND /LAND/
DLOAD DSU
TLAND
GUIDDURN
STCALL TDEC1 # INTEGRATE STATE FORWARD TO THAT TIME
LEMPREC
SSP VLOAD
NIGNLOOP
40D
UNITX
STOVL CG
UNITY
STOVL CG +6
UNITZ
STODL CG +14
99999CON
STOVL DELTAH # INITIALIZE DELTAH FOR V16N68 DISPLAY
ZEROVECS
STODL UNFC/2 # INITIALIZE TRIM VELOCITY CORRECTION TERM
HI6ZEROS
STORE TTF/8
IGNALOOP DLOAD
TAT
STOVL PIPTIME1
RATT1
VSL4 MXV
REFSMMAT
STCALL R
MUNGRAV
STCALL GDT/2
?GUIDSUB # WHICH DELIVERS N PASSES OF GUIDANCE
# DDUMCALC IS PROGRAMMED AS FOLLOWS:-
# 2 -
# (RIGNZ - RGU )/16 + 16(RGU )KIGNY/B8 + (RGU - RIGNX)KIGNX/B4 + (ABVAL(VGU) - VIGN)KIGNV/B4
# 2 1 0
# DDUM = -------------------------------------------------------------------------------------------
# 10
# 2 (VGU - 16 VGU KIGNX/B4)
## Page 782
# 2 0
# THE NUMERATOR IS SCALED IN METERS AT 2(28). THE DENOMINATOR IS A VELOCITY IN UNITS OF 2(10) M/CS.
# THE QUOTIENT IS THUS A TIME IN UNITS OF 2(18) CENTISECONDS. THE FINAL SHIFT RESCALES TO UNITS OF 2(28) CS.
# THERE IS NO DAMPING FACTOR. THE CONSTANTS KIGNX/B4, KIGNY/B8 AND KIGNV/B4 ARE ALL NEGATIVE IN SIGN.
DDUMCALC TS NIGNLOOP
TC INTPRET
DLOAD DMPR # FORM DENOMINATOR FIRST
VGU
KIGNX/B4
SL4R BDSU
VGU +4
PDDL DSU
RIGNZ
RGU +4
SR4R PDDL
RGU +2
DSQ DMPR
KIGNY/B8
SL4R PDDL
RGU
DSU DMPR
RIGNX
KIGNX/B4
PDVL ABVAL
VGU
DSU DMPR
VIGN
KIGNV/B4
DAD DAD
DAD DDV
SRR
10D
PUSH DAD
PIPTIME1
STODL TDEC1 # STORE NEW GUESS FOR NEXT INTEGRATION
ABS DSU
DDUMCRIT
BMN CALL
DDUMGOOD
INTSTALL
SET SET
INTYPFLG
MOONFLAG
DLOAD
PIPTIME1
STOVL TET # HOPEFULLY ?GUIDSUB DID NOT
RATT1 # CLOBBER RATT1 AND VATT1
## Page 783
STOVL RCV
VATT1
STCALL VCV
INTEGRVS
GOTO
IGNALOOP
DDUMGOOD SLOAD SR
ZOOMTIME
14D
BDSU
TDEC1
STOVL TIG # COMPUTE DISTANCE LANDING SITE WILL BE
V # OUT OF LM'S ORBITAL PLANE AT IGNITION:
VXV UNIT # SIGN IS + IF LANDING SITE IS TO THE
R # RIGHT, NORTH; - IF TO THE LEFT, SOUTH.
DOT SL1
LAND
R60INIT STOVL OUTOFPLN # INITIALIZATION FOR CALCMANU
UNFC/2
STORE R60VSAVE # STORE UNFC/2 TEMPORARILY IN R60SAVE
EXIT
# ****************************************
IGNALGRT TC PHASCHNG # PREVENT REPEATING IGNALG
OCT 04024
ASTNCLOK CS ASTNDEX
TC BANKCALL
CADR STCLOK2
TCF ENDOFJOB # RETURN IN NEW JOB AND IN EBANK FIVE
ASTNRET TC INTPRET
SSP RTB # GO PICK UP DISPLAY AT END OF R51:
QMAJ # "PROCEED" WILL DO A FINE ALIGNMENT
FCADR P63SPOT2 # "ENTER" WILL RETURN TO P63SPOT2
R51P63
P63SPOT2 VLOAD UNIT # INITIALIZE KALCMANU FOR BURN ATTITUDE
R60VSAVE
STOVL POINTVSM
UNITX
STORE SCAXIS
EXIT
CAF EBANK7
TS EBANK
INHINT
TC IBNKCALL
CADR PFLITEDB
## Page 784
RELINT
TC BANKCALL
CADR R60LEM
TC PHASCHNG # PREVENT RECALLING R60
OCT 04024
P63SPOT3 CA BIT6 # IS THE LR ANTENNA IN POSITION 1 YET
EXTEND
RAND CHAN33
EXTEND
BZF P63SPOT4 # BRANCH IF ANTENNA ALREADY IN POSITION 1
CAF CODE500 # ASTRONAUT: PLEASE CRANK THE
TC BANKCALL # SILLY THING AROUND
CADR GOPERF1
TCF GOTOPOOH # TERMINATE
TCF P63SPOT3 # PROCEED SEE IF HE'S LYING
P63SPOT4 TC BANKCALL # ENTER INITIALIZE LANDING RADAR
CADR SETPOS1
TC POSTJUMP # OFF TO SEE THE WIZARD ...
CADR BURNBABY
# ----------------------------------------
# CONSTANTS FOR P63LM AND IGNALG
P63ADRES GENADR P63TABLE
ASTNDEX = MD1 # OCT 25; INDEX FOR CLOKTASK
CODE500 OCT 00500
99999CON 2DEC 30479.7 B-24
GUIDDURN 2DEC +66440 # GUIDDURN +6.64400314 E+2
DDUMCRIT 2DEC +8 B-28 # CRITERION FOR IGNALG CONVERGENCE
## Page 785
# ----------------------------------------
## Page 786
# ****************************************
# P68: LANDING CONFIRMATION
# ****************************************
BANK 34
SETLOC F2DPS*34
BANK
COUNT* $$/P6567
LANDJUNK TC PHASCHNG
OCT 04024
INHINT
TC BANKCALL # ZERO ATTITUDE ERROR
CADR ZATTEROR
TC INTPRET # TO INTERPRETIVE AS TIME IS NOT CRITICAL
SET # PREVENT RCS JET FIRINGS IF MODE CONT IS
PULSEFLG # IN ATT HOLD
SET CLEAR
SURFFLAG
LETABORT
SET VLOAD
APSFLAG
RN
STODL ALPHAV
PIPTIME
SET CALL
LUNAFLAG
LAT-LONG
SETPD VLOAD # COMPUTE RLS AND STORE IT AWAY
0
RN
VSL2 PDDL
PIPTIME
PUSH CALL
R-TO-RP
STORE RLS
EXIT
CAF V06N43* # ASTRONAUT: NOW LOOK WHERE YOU ENDED UP
TC BANKCALL
CADR GOFLASH
TCF GOTOPOOH # TERMINATE
TCF +2 # PROCEED
TCF -5 # RECYCLE
TC INTPRET
VLOAD # INITIALIZE GSAV AND (USING REFMF)
## Page 787
UNITX # YNBSAV, ZNBSAV AND ATTFLAG FOR P57
STCALL GSAV
REFMF
EXIT
TCF GOTOPOOH # ASTRONAUT: PLEASE SELECT P57
V06N43* VN 0643
