Source Code

These source-code files were obtained by digitally photographing an Artemis 72 (Apollo 15-17 Command Module) program listing from a private collection and then modifying pre-existing Comanche 55 (Apollo 11) source files to incorporate changes. Photography was by Ron Burkey, and transcription was performed by a team of volunteers. Note that the page images presented online are of reduced quality, and that additional images may be available. Report any conversion errors or legibility problems in page images to info@sandroid.org. Notations on the program listing read, in part:

	GAP: ASSEMBLE REVISION 072 OF AGC PROGRAM ARTEMIS 
	BY NASA 2021114-011 11:40 FEB. 26, 1971
Note that the date is the date of the printout, not the date of the program revision.

018489,000002:                                                                                                  ## Copyright:   Public domain.
018490,000003:                                                                                                  ## Filename:    GIMBAL_LOCK_AVOIDANCE.agc
018491,000004:                                                                                                  ## Purpose:     Part of the source code for Artemis (i.e., Colossus 3),
018492,000005:                                                                                                  ##              build 072.  This is for the Command Module's (CM) 
018493,000006:                                                                                                  ##              Apollo Guidance Computer (AGC), for 
018494,000007:                                                                                                  ##              Apollo 15-17.
018495,000008:                                                                                                  ## Assembler:   yaYUL
018496,000009:                                                                                                  ## Contact:     Sergio Navarro <sergionavarrog@gmail.com>
018497,000010:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
018498,000011:                                                                                                  ## Page Scans:  www.ibiblio.org/apollo/ScansForConversion/Artemis072/
018499,000012:                                                                                                  ## Mod history: 2009-08-19 SN   Adapted from corresponding Comanche 055 file.
018500,000013:                                                                                                  ##              2009-09-04 JL   Minor changes.
018501,000014:                                                                                                  ##              2010-02-20 RSB  Un-##'d this header.
018502,000015:                                                                                                  ##              2017-02-05 RSB  Proofed comment text by diff'ing vs Comanche 55
018503,000016:                                                                                                  ##                              but no differences found.
018504,000017: 

Page 416

018506,000019: 
018507,000020: 22,2000                                           SETLOC   KALCMON1                              
018508,000021: 22,2000                                           BANK                                           
018509,000022: 
018510,000023: 22,2745                                           COUNT*   $$/KALC                               
018511,000024: 22,2745  E6,1661                                  EBANK=   BCDU                                  
018512,000025: 
018513,000026:                                                                                                  #  DETECTING GIMBAL LOCK
018514,000027: 22,2745  22,2745               LOCSKIRT           EQUALS   WCALC                                 
018515,000028: 22,2745           70740        WCALC              LXC,1    DLOAD*                                
018516,000029: 22,2746           00774                                    RATEINDX                              
018517,000030: 22,2747           05002                                    ARATE,1                               
018518,000031: 22,2750           45002                           SR4      CALL                                  #  COMPUTE THE INCREMENTAL ROTATION MATRIX
018519,000032: 22,2751           44522                                    DELCOMP                               #  DEL CORRESPONDING TO A 1 SEC ROTATION
018520,000033:                                                                                                  #  ABOUT COF
018521,000034: 22,2752           74343                           DLOAD*   VXSC                                  
018522,000035: 22,2753           05002                                    ARATE,1                               
018523,000036: 22,2754           03343                                    COF                                   
018524,000037: 22,2755           77721                           MXV                                            
018525,000038: 22,2756           05014                                    QUADROT                               
018526,000039: 22,2757           17311                           STODL    BRATE                                 
018527,000040: 22,2760           03365                                    AM                                    
018528,000041: 22,2761           55605                           DMP      DDV*                                  
018529,000042: 22,2762           05012                                    ANGLTIME                              
018530,000043: 22,2763           05002                                    ARATE,1                               
018531,000044: 22,2764           77661                           SR                                             
018532,000045: 22,2765           20606                                    5                                     
018533,000046: 22,2766           03317                           STORE    TM                                    
018534,000047: 22,2767           77214                           BON      VLOAD                                 
018535,000048: 22,2770           00313                                    CYC61FLG                              
018536,000049: 22,2771           71747                                    RCYCLR61                              
018537,000050: 22,2772           03311                                    BRATE                                 
018538,000051: 22,2773           77761                           VXSC                                           
018539,000052: 22,2774           05036                                    BIASCALE                              
018540,000053: 22,2775           03275                           STORE    BIASTEMP                              #  ATTITUDE ERROR BIAS TO PREVENT OVERSHOOT
018541,000054:                                                                                                  #  IN SYSTEM
018542,000055: 22,2776           77614                           SETGO                                          #  STATE SWITCH CALCMAN2 (43D)
018543,000056: 22,2777           01035                                    CALCMAN2                              #  0(OFF) = BYPASS STARTING PROCEDURE
018544,000057: 22,3000           45053                                    NEWANGL    +1                         #  1(ON) = START MANEUVER
018545,000058: 
018546,000059: 
018547,000060: 22,3001           00044 15053  ARATE              2DEC     .0022222222                            #  = .05 DEG/SEC
018548,000061: 22,3003           00221 24255                     2DEC     .0088888889                            #  = .2 DEG/SEC
018549,000062: 22,3005           00554 02660                     2DEC     .0222222222                            #  = .5 DEG/SEC
018550,000063: 22,3007           02660 13301                     2DEC     .0888888889                            #  = 2 DEG/SEC                $22.5 DEG/SEC
018551,000064: 22,3011           00003 04000  ANGLTIME           2DEC     .000190735                            #  = 100B - 19
018552,000065:                                                                                                  #  MANEUVER ANGLE TO MANEUVER TIME

Page 417

018554,000067: 22,3013           03146 14632  QUADROT            2DEC     .1                                    #  ROTATION MATRIX FROM S/C AXES TO CONTROL
018555,000068: 22,3015           00000 00000                     2DEC     0          B-28                       #  AXES (X ROT = -7.25 DEG)
018556,000069: 22,3017           00000 00000                     2DEC     0          B-28                       
018557,000070: 22,3021           00000 00000                     2DEC     0          B-28                       
018558,000071: 22,3023           03131 11275                     2DEC     .099200                               #  =(.1)COS7.25
018559,000072: 22,3025           77461 47370                     2DEC     -.012620                              #  =-(.1)SIN7.25
018560,000073: 22,3027           00000 00000                     2DEC     0          B-28                       
018561,000074: 22,3031           00316 30407                     2DEC     .012620                               #  (.1)SIN7.25
018562,000075: 22,3033           03131 11275                     2DEC     .099200                               #  (.1)COS7.25
018563,000076: 22,3035           00004 05253  BIASCALE           2DEC     .0002543132                            #  = (450/180)(1/0.6)(1/16384)

End of include-file GIMBAL_LOCK_AVOIDANCE.agc.  Parent file is MAIN.agc