Source Code

This source code is very close to the Apollo Guidance Computer software for the Apollo 13 Lunar module. This revision of the Luminary 131 program is from December of 1969, whereas there was a later revision in January of 1970, and still another revision in February, which is the code that flew on the mission. As far as this transcription is concerned, it was originally from a copy made in 1991 of a printout from the collection of AGC developer Don Eyles for collector David Craig. It was subsequently scanned by Gary Neff, reprocessed for online presentation at the now-discontinued History of Recent Science and Technology (HRST) website of MIT's Dibner Institute (the full-quality scans being discarded in the process), and finally transcribed by Ron Burkey for the Virtual AGC Project. Although a high-quality replacement scan for a completely illegible page was later provided by Gary Neff, the reduced legibility of the reprocessed HRST posting nevertheless caused many errors to be introduced into the transcription. Accordingly, a second scan of the same physical printout was made in 2017 for the Virtual AGC Project's collection at the Internet Archive, and used to correct the transcription errors. All of the scanned materials mentioned, as well as other Luminary 131 related material, are available online. Don Eyles apprently made additional hand-written notes in printout between 1991 and 2017, so the two scans are not identical in that respect. The page-headings in the printout read, in part:
	GAP:  ASSEMBLE REVISION 131 OF AGC PROGRAM LUMINARY BY NASA 2021112-091
	17:53 DEC. 19, 1969
Note that the date is the date the printout was made, not the date on which the program revision was released, although these happen to be very close together.

015241,000002:                                                                                                  ## Copyright:   Public domain.
015242,000003:                                                                                                  ## Filename:    KALCMANU_STEERING.agc
015243,000004:                                                                                                  ## Purpose:     A section of Luminary 1C, revision 131.
015244,000005:                                                                                                  ##              It is part of the source code for the Lunar Module's (LM)
015245,000006:                                                                                                  ##              Apollo Guidance Computer (AGC) for Apollo 13.
015246,000007:                                                                                                  ##              This file is intended to be a faithful transcription, except
015247,000008:                                                                                                  ##              that the code format has been changed to conform to the
015248,000009:                                                                                                  ##              requirements of the yaYUL assembler rather than the 
015249,000010:                                                                                                  ##              original YUL assembler.
015250,000011:                                                                                                  ## Reference:   pp. 367-371
015251,000012:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
015252,000013:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
015253,000014:                                                                                                  ## Mod history: 05/11/03 RSB    Began transcribing.
015254,000015:                                                                                                  ##              05/14/05 RSB    Corrected website reference above.
015255,000016:                                                                                                  ##              2011-05-07 JL   Removed workarounds.
015256,000017:                                                                                                  ##              2017-01-06 RSB  Page numbers now agree with those on the
015257,000018:                                                                                                  ##                              original harcopy, as opposed to the PDF page
015258,000019:                                                                                                  ##                              numbers in 1701.pdf.
015259,000020:                                                                                                  ##              2017-01-28 RSB  WTIH -> WITH.
015260,000021:                                                                                                  ##              2017-02-23 RSB  Proofed comment text using octopus/ProoferComments.
015261,000022:                                                                                                  ##              2017-02-28 RSB  Fixed lingering typos.
015262,000023:                                                                                                  ##              2017-03-17 RSB  Comment-text fixes identified in diff'ing
015263,000024:                                                                                                  ##                              Luminary 99 vs Comanche 55.
015264,000025: 

Page 367

015266,000027:                                                                                                  #  GENERATION OF STEERING COMMANDS FOR DIGITAL AUTOPILOT FREE FALL MANEUVERS
015267,000028: 
015268,000029:                                                                                                  #  NEW COMMANDS WILL BE GENERATED EVERY ONE SECOND DURING THE MANEUVER
015269,000030: 
015270,000031: 22,3003  E6,1706                                  EBANK=   TTEMP                                 
015271,000032: 
015272,000033: 22,3003           04616        NEWDELHI           TC       BANKCALL                              #  CHECK FOR AUTO STABILIZATION
015273,000034: 22,3004           54266                           CADR     ISITAUTO                              #  ONLY
015274,000035: 22,3005           10000                           CCS      A                                     
015275,000036: 22,3006           12730                           TCF      NOGO       -2                         
015276,000037: 22,3007           06042        NEWANGL            TC       INTPRET                               
015277,000038: 22,3010           75160                           AXC,1    AXC,2                                 
015278,000039: 22,3011           03245                                    MIS                                   #  COMPUTE THE NEW MATRIX FROM S/C TO
015279,000040: 22,3012           02230                                    KEL                                   #  STABLE MEMBER AXES
015280,000041: 22,3013           77624                           CALL                                           
015281,000042: 22,3014           44312                                    MXM3                                  
015282,000043: 22,3015           45575                           VLOAD    STADR                                 
015283,000044: 22,3016           50515                           STOVL    MIS        +12D                       #  CALCULATE NEW DESIRED CDU ANGLES
015284,000045: 22,3017           77626                           STADR                                          
015285,000046: 22,3020           50523                           STOVL    MIS        +6D                        
015286,000047: 22,3021           77626                           STADR                                          
015287,000048: 22,3022           74531                           STORE    MIS                                   
015288,000049: 22,3023           45160                           AXC,1    CALL                                  
015289,000050: 22,3024           03245                                    MIS                                   
015290,000051: 22,3025           44654                                    DCMTOCDU                              #  PICK UP THE NEW CDU ANGLES FROM MATRIX
015291,000052: 22,3026           77634                           RTB                                            
015292,000053: 22,3027           21621                                    V1STO2S                               
015293,000054: 22,3030           03303                           STORE    NCDU                                  #  NEW CDU ANGLES
015294,000055: 22,3031           77414                           BONCLR   EXIT                                  
015295,000056: 22,3032           01215                                    CALCMAN2                              
015296,000057: 22,3033           45122                                    MANUSTAT                              #  TO START MANEUVER
015297,000058: 22,3034           34752                           CAF      TWO                                   #        +0 OTHERWISE
015298,000059: 22,3035           55261        INCRDCDU           TS       SPNDX                                 
015299,000060: 22,3036           51261                           INDEX    SPNDX                                 
015300,000061: 22,3037           31675                           CA       BCDU                                  #  INITIAL CDU ANGLES
015301,000062: 22,3040           00006                           EXTEND                                         #  OR PREVIOUS DESIRED CDU ANGLES
015302,000063: 22,3041           51261                           INDEX    SPNDX                                 
015303,000064: 22,3042           21702                           MSU      NCDU                                  
015304,000065: 22,3043           00006                           EXTEND                                         
015305,000066: 22,2000                                           SETLOC   KALCMON1                              
015306,000067: 22,2000                                           BANK                                           
015307,000068: 
015308,000069: 22,3044           73121                           MP       DT/TAU                                
015309,000070: 22,3045           10000                           CCS      A                                     #  CONVERT TO 2S COMPLEMENT
015310,000071: 22,3046           64753                           AD       ONE                                   
015311,000072: 22,3047           13051                           TCF      +2                                    
015312,000073: 22,3050           40000                           COM                                            
015313,000074: 22,3051           51261                           INDEX    SPNDX                                 
015314,000075: 22,3052           55637                           TS       DELDCDU                               #  ANGLE INCREMENTS TO BE ADDED TO
015315,000076: 22,3053           51261                           INDEX    SPNDX                                 #  CDUXD, CDUYD, CDUZD EVERY TENTH SECOND

Page 368

015317,000078: 22,3054           31702                           CA       NCDU                                  #  BY LEM DAP
015318,000079: 22,3055           51261                           INDEX    SPNDX                                 
015319,000080: 22,3056           57675                           XCH      BCDU                                  
015320,000081: 22,3057           51261                           INDEX    SPNDX                                 
015321,000082: 22,3060           55634                           TS       CDUXD                                 
015322,000083: 22,3061           11261                           CCS      SPNDX                                 
015323,000084: 22,3062           13035                           TCF      INCRDCDU                              #  LOOP FOR THREE AXES
015324,000085: 
015325,000086: 22,3063           00003                           RELINT                                         
015326,000087: 
015327,000088:                                                                                                  #  COMPARE PRESENT TIME WITH TIME TO TERMINATE MANEUVER
015328,000089: 
015329,000090: 22,3064           03075        TMANUCHK           TC       TIMECHK                               
015330,000091: 22,3065           13170                           TCF      CONTMANU                              
015331,000092: 22,3066           34753                           CAF      ONE                                   
015332,000093: 22,3067           00004        MANUSTAL           INHINT                                         #  END MAJOR PART OF MANEUVER WITHIN 1 SEC
015333,000094: 22,3070           05203                           TC       WAITLIST                              #  UNDER WAITLIST CALL TO MANUSTOP
015334,000095: 22,3071  E6,1706                                  EBANK=   TTEMP                                 
015335,000096: 22,3071           03213 44066                     2CADR    MANUSTOP                              
015336,000097: 
015337,000098: 22,3073           00003                           RELINT                                         
015338,000099: 22,3074           15155                           TCF      ENDOFJOB                              
015339,000100: 
015340,000101: 22,3075           00006        TIMECHK            EXTEND                                         
015341,000102: 22,3076           40025                           DCS      TIME2                                 
015342,000103: 22,3077           53707                           DXCH     TTEMP                                 
015343,000104: 22,3100           00006                           EXTEND                                         
015344,000105: 22,3101           31733                           DCA      TM                                    
015345,000106: 22,3102           21707                           DAS      TTEMP                                 
015346,000107: 22,3103           11706                           CCS      TTEMP                                 
015347,000108: 22,3104           00002                           TC       Q                                     
015348,000109: 22,3105           13107                           TCF      +2                                    
015349,000110: 22,3106           13117                           TCF      2NDRETRN                              
015350,000111: 22,3107           11707                           CCS      TTEMP      +1                         
015351,000112: 22,3110           00002                           TC       Q                                     
015352,000113: 22,3111           13113                           TCF      MANUOFF                               
015353,000114: 22,3112           40000                           COM                                            
015354,000115: 22,3113           63166        MANUOFF            AD       ONESEK     +1                         
015355,000116: 22,3114           00006                           EXTEND                                         
015356,000117: 22,3115           63117                           BZMF     2NDRETRN                              
015357,000118: 22,3116           24002                           INCR     Q                                     
015358,000119: 22,3117           24002        2NDRETRN           INCR     Q                                     
015359,000120: 22,3120           00002                           TC       Q                                     
015360,000121: 
015361,000122: 22,3121           03146        DT/TAU             DEC      .1                                    
015362,000123: 
015363,000124: 22,3122           77776        MANUSTAT           EXIT                                           #  INITIALIZATION ROUTINE
015364,000125: 22,3123           00006                           EXTEND                                         #  FOR AUTOMATIC MANEUVERS
015365,000126: 22,3124           30025                           DCA      TIME2                                 

Page 369

015367,000128: 22,3125           21733                           DAS      TM                                    #  TM+T0         MANEUVER COMPLETION TIME
015368,000129: 22,3126           00006                           EXTEND                                         
015369,000130: 22,3127           43166                           DCS      ONESEK                                
015370,000131: 22,3130           21733                           DAS      TM                                    #  (TM+T0)-1
015371,000132: 22,3131           00004                           INHINT                                         
015372,000133: 22,3132           34752                           CAF      TWO                                   
015373,000134: 22,3133           55700        RATEBIAS           TS       KSPNDX                                
015374,000135: 22,3134           60000                           DOUBLE                                         
015375,000136: 22,3135           55701                           TS       KDPNDX                                
015376,000137: 22,3136           50000                           INDEX    A                                     
015377,000138: 22,3137           31724                           CA       BRATE                                 
015378,000139: 22,3140           51700                           INDEX    KSPNDX                                #  STORE MANEUVER RATE IN
015379,000140: 22,3141           55642                           TS       OMEGAPD                               #  OMEGAPD, OMEGAQD, OMEGARD
015380,000141: 22,3142           00006                           EXTEND                                         
015381,000142: 22,3143           63145                           BZMF     +2                                    #  COMPUTE ATTITUDE ERROR
015382,000143: 22,3144           40000                           COM                                            #  OFFSET = (WX)ABS(WX)/2AJX
015383,000144: 22,3145           00006                           EXTEND                                         #  WHERE AJX= 2-JET ACCELERATION
015384,000145: 22,3146           73167                           MP       BIASCALE                              #  = -1/16
015385,000146: 22,3147           00006                           EXTEND                                         
015386,000147: 22,3150           51701                           INDEX    KDPNDX                                
015387,000148: 22,3151           71724                           MP       BRATE                                 
015388,000149: 22,3152           00006                           EXTEND                                         
015389,000150: 22,3153           51700                           INDEX    KSPNDX                                
015390,000151: 22,3154           11530                           DV       1JACC                                 #  = AJX  $ 90 DEG/SEC-SEC
015391,000152: 22,3155           51700                           INDEX    KSPNDX                                
015392,000153: 22,3156           55274                           TS       DELPEROR                              #       $ 180 DEG
015393,000154: 22,3157           11700                           CCS      KSPNDX                                
015394,000155: 22,3160           13133                           TCF      RATEBIAS                              
015395,000156: 
015396,000157: 22,3161           30025                           CA       TIME1                                 
015397,000158: 22,3162           63166                           AD       ONESEK     +1                         
015398,000159: 22,3163           57705                           XCH      NEXTIME                               
015399,000160: 22,3164           13034                           TCF      INCRDCDU   -1                         
015400,000161: 
015401,000162: 22,3165           00000        ONESEK             DEC      0          B-14                       
015402,000163: 22,3166           00144                           DEC      100        B-14                       
015403,000164: 
015404,000165: 22,3167           75777        BIASCALE           OCT      75777                                 #  = -1/16
015405,000166: 
015406,000167: 22,3170           40025        CONTMANU           CS       TIME1                                 #  RESET FOR NEXT DCDU UPDATE
015407,000168: 22,3171           61705                           AD       NEXTIME                               
015408,000169: 22,3172           10000                           CCS      A                                     
015409,000170: 22,3173           64753                           AD       ONE                                   
015410,000171: 22,3174           13177                           TCF      MANUCALL                              
015411,000172: 22,3175           64735                           AD       NEGMAX                                
015412,000173: 22,3176           40000                           COM                                            
015413,000174: 22,3177           00004        MANUCALL           INHINT                                         #  CALL FOR NEXT UPDATE VIA WAITLIST
015414,000175: 22,3200           05203                           TC       WAITLIST                              
015415,000176: 22,3201  E6,1706                                  EBANK=   TTEMP                                 
015416,000177: 22,3201           03206 44066                     2CADR    UPDTCALL                              

Page 370

015418,000179: 22,3203           33166                           CAF      ONESEK     +1                         #  INCREMENT TIME FOR NEXT UPDATE
015419,000180: 22,3204           27705                           ADS      NEXTIME                               
015420,000181: 22,3205           15155                           TCF      ENDOFJOB                              
015421,000182: 
015422,000183: 22,3206           37717        UPDTCALL           CAF      PRIO26                                #  SATELLITE PROGRAM TO CALL FOR UPDATE
015423,000184: 22,3207           05105                           TC       FINDVAC                               #  OF STEERING COMMANDS
015424,000185: 22,3210  E6,1706                                  EBANK=   TTEMP                                 
015425,000186: 22,3210           03003 44066                     2CADR    NEWDELHI                              
015426,000187: 
015427,000188: 22,3212           05261                           TC       TASKOVER                              
015428,000189: 

Page 371

015430,000191:                                                                                                  #  ROUTINE FOR TERMINATING AUTOMATIC MANEUVERS
015431,000192: 
015432,000193: 22,3213           34755        MANUSTOP           CAF      ZERO                                  #  ZERO MANEUVER RATES
015433,000194: 22,3214           55641                           TS       DELDCDU2                              
015434,000195: 22,3215           55644                           TS       OMEGARD                               
015435,000196: 22,3216           55276                           TS       DELREROR                              
015436,000197: 22,3217           55640                           TS       DELDCDU1                              
015437,000198: 22,3220           55643                           TS       OMEGAQD                               
015438,000199: 22,3221           55275                           TS       DELQEROR                              
015439,000200: 22,3222           30323                           CA       CPSI                                  #  SET DESIRED GIMBAL ANGLES TO
015440,000201: 22,3223           55636                           TS       CDUZD                                 #  DESIRED FINAL GIMBAL ANGLES
015441,000202: 22,3224           30322                           CA       CTHETA                                
015442,000203: 22,3225           55635                           TS       CDUYD                                 
015443,000204: 22,3226           30321        ENDROLL            CA       CPHI                                  #  NO FINAL YAW
015444,000205: 22,3227           55634                           TS       CDUXD                                 
015445,000206: 22,3230           34755                           CAF      ZERO                                  
015446,000207: 22,3231           55642                           TS       OMEGAPD                               #  I.E. MANEUVER DID NOT GO THRU
015447,000208: 22,3232           55637                           TS       DELDCDU                               #  GIMBAL LOCK ORIGINALLY
015448,000209: 22,3233           55274                           TS       DELPEROR                              
015449,000210: 22,3234           31306        GOODMANU           CA       ATTPRIO                               #  RESTORE USERS PRIO
015450,000211: 22,3235           54063                           TS       NEWPRIO                               
015451,000212: 
015452,000213: 22,3236           34755                           CA       ZERO                                  #  ZERO ATTCADR
015453,000214: 22,3237           53305                           DXCH     ATTCADR                               
015454,000215: 
015455,000216: 22,3240           05116                           TC       SPVAC                                 #  RETURN TO USER
015456,000217: 
015457,000218: 22,3241           05261                           TC       TASKOVER                              
015458,000219: 
015459,000220: 

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