### FILE="Main.annotation"
## Copyright:   Public domain.
## Filename:    GIMBAL_LOCK_AVOIDANCE.agc
## Purpose:     A section of Luminary revision 96.
##              It is part of the reconstructed source code for the
##              original release of the flight software for the Lunar 
##              Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
##              The code has been recreated from a previously reconstructed
##              copy of Luminary 97 by undoing changes described in anomaly
##              report LNY-59. The code has been adapted such that the
##              resulting bugger words exactly match those specified for
##              Luminary 96 in NASA drawing 2021152D, which gives relatively
##              high confidence that the reconstruction is correct.
## Reference:   p.  364
## Assembler:   yaYUL
## Contact:     Ron Burkey <info@sandroid.org>.
## Website:     www.ibiblio.org/apollo/index.html
## Mod history: 2019-08-04 MAS  Created from Luminary 97.

## Page 364
		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