### FILE="Main.annotation"
## Copyright:	Public domain.
## Filename:	GIMBAL_LOCK_AVOIDANCE.agc
## Purpose:	Part of the source code for Colossus build 237.  
##		This is for the Command Module's (CM) Apollo Guidance
##		Computer (AGC), for Apollo 8.
## Assembler:	yaYUL
## Contact:	Onno Hommes <ohommes@alumni.cmu.edu>
## Website:	www.ibiblio.org/apollo/index.html
## Page Scans:	www.ibiblio.org/apollo/ScansForConversion/Colossus237/
## Mod history:	2010-06-01 OH	Adapted from corresponding Colossus 249 file.
##		2010-12-04 JL	Remove Colossus 249 header comments. Change 
##				to double-hash page numbers.
##		2011-01-27 JL	Minor fixes.
##		2016-12-30 RSB	Proofed comment text using octopus/ProoferComments,
##				and corrected errors found.

## Page 403
		BANK	15
		SETLOC	KALCMON1
		BANK

		EBANK=	BCDU

# DETECTING GIMBAL LOCK
LOCSKIRT	EQUALS	NOGIMLOC

NOGIMLOC	SET
			CALCMAN3
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
		STOVL	TM	
			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	.1777777777	# = 4 DEG/SEC		    $ 22.5 DEG/SEC
ANGLTIME	2DEC	.000190735	# = 100B - 19 
#					  MANEUVER ANGLE TO MANEUVER TIME
## Page 404
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)