### FILE="Main.annotation"
## Copyright:   Public domain.
## Filename:    GIMBAL_LOCK_AVOIDANCE.agc
## Purpose:     A section of LUM69 revision 2.
##              It is part of the reconstructed source code for the flown
##              version of the flight software for the Lunar Module's (LM)
##              Apollo Guidance Computer (AGC) for Apollo 10. The code has
##              been recreated from a copy of Luminary revsion 069, using
##              changes present in Luminary 099 which were described in
##              Luminary memos 75 and 78. The code has been adapted such
##              that the resulting bugger words exactly match those specified
##              for LUM69 revision 2 in NASA drawing 2021152B, which gives
##              relatively high confidence that the reconstruction is correct.
## Reference:   p.  377
## Assembler:   yaYUL
## Contact:     Ron Burkey <info@sandroid.org>.
## Website:     www.ibiblio.org/apollo/index.html
## Mod history: 2019-07-27 MAS  Created from Luminary 69.

## Page 377
		BANK	15
		
		SETLOC	KALCMON1
		BANK
		
# DETECTING GIMBAL LOCK
LOCSKIRT	EQUALS	NOGIMLOC

NOGIMLOC	SET
			CALCMAN3
WCALC		LXC,1	DLOAD*
			RATEINDX	# CHOOSE THE DESIRED MANEUVER RATE
			ARATE,1		# FROM A LIST OF FOUR
		SR4	CALL		# COMPUTE THE INCREMENTAL ROTATION MATRIX
			DELCOMP		# DEL CORRESPONDING TO A 1 SEC ROTATION
					# ABOUT COF
		DLOAD*	VXSC
			ARATE,1
			COF
		STODL	BRATE		# COMPONENT MANEUVER RATES 45 DEG/SEC
			AM
		DMP	DDV*
			ANGLTIME
			ARATE,1
		SR
			5
		STORE	TM		# MANEUVER EXECUTION TIME SCALED AS T2
		SETGO	
			CALCMAN2	# 0(OFF) = CONTINUE MANEUVER
			NEWANGL +1	# 1(ON) = START MANEUVER
			
# THE FOUR SELECTABLE FREE FALL MANEUVER RATES SELECTED BY
# LOADING RATEINDX WITH 0, 2, 4, 6, RESPECTIVELY

ARATE		2DEC	.0088888888	# = 0.2 DEG/SEC		$ 22.5 DEG/SEC

		2DEC	.0222222222	# = 0.5 DEG/SEC		$ 22.5 DEG/SEC
		
		2DEC	.0888888888	# = 2.0 DEG/SEC		$ 22.5 DEG/SEC
		
		2DEC	.4444444444	# = 10.0 DEG/SEC	$ 22.5 DEG/SEC
		
ANGLTIME	2DEC	.0001907349	# = 100B-19 FUDGE FACTOR TO CONVERT
					# MANEUVER ANGLE TO MANEUVER TIME