### FILE="Main.annotation"
## Copyright:   Public domain.
## Filename:    GIMBAL_LOCK_AVOIDANCE.agc
## Purpose:     A section of Artemis revision 071.
##              It is part of the reconstructed source code for the first
##              release of the flight software for the Command Module's
##              (CM) Apollo Guidance Computer (AGC) for Apollo 15 through
##              17. The code has been recreated from a copy of Artemis 072.
##              It has been adapted such that the resulting bugger words
##              exactly match those specified for Artemis 071 in NASA
##              drawing 2021154-, which gives relatively high confidence
##              that the reconstruction is correct.
## Reference:   416
## Assembler:   yaYUL
## Contact:     Ron Burkey <info@sandroid.org>.
## Website:     www.ibiblio.org/apollo/index.html
## Mod history: 2019-08-14 MAS  Created from Artemis 072.

## Page 416
		
		SETLOC	KALCMON1
		BANK
		
		COUNT*	$$/KALC
		EBANK=	BCDU
		
# DETECTING GIMBAL LOCK
LOCSKIRT	EQUALS	WCALC
WCALC		LXC,1	DLOAD*
			RATEINDX
			ARATE,1	
		SR4	CALL		# COMPUTE THE INCREMENTAL ROTATION MATRIX
			DELCOMP		# DEL CORRESPONDING TO A 1 SEC ROTATION
					# ABOUT COF
		DLOAD*	VXSC
			ARATE,1
			COF
		MXV
			QUADROT
		STODL	BRATE	
			AM
		DMP	DDV*
			ANGLTIME
			ARATE,1
		SR
			5
		STORE	TM
		BON	VLOAD
			CYC61FLG
			RCYCLR61
			BRATE
		VXSC
			BIASCALE
		STORE	BIASTEMP	# ATTITUDE ERROR BIAS TO PREVENT OVERSHOOT
					# IN SYSTEM
		SETGO			# STATE SWITCH CALCMAN2 (43D)
			CALCMAN2	# 0(OFF) = BYPASS STARTING PROCEDURE
			NEWANGL +1	# 1(ON) = START MANEUVER
			
			
ARATE		2DEC	.0022222222	# = .05 DEG/SEC
		2DEC	.0088888889	# = .2 DEG/SEC
		2DEC	.0222222222	# = .5 DEG/SEC
		2DEC	.0888888889	# = 2 DEG/SEC                $22.5 DEG/SEC
ANGLTIME	2DEC	.000190735	# = 100B - 19
					# MANEUVER ANGLE TO MANEUVER TIME
## Page 417
QUADROT		2DEC	.1		# ROTATION MATRIX FROM S/C AXES TO CONTROL
		2DEC	0		# AXES (X ROT = -7.25 DEG)
		2DEC	0
		2DEC	0
		2DEC	.099200		# =(.1)COS7.25
		2DEC	-.012620	# =-(.1)SIN7.25
		2DEC	0
		2DEC	.012620		# (.1)SIN7.25
		2DEC	.099200		# (.1)COS7.25
BIASCALE	2DEC	.0002543132	# = (450/180)(1/0.6)(1/16384)