Source Code

These source-code files are part of a reconstructed copy of Luminary 96, the original release of the Apollo 11 Lunar Module (LM) Apollo Guidance Computer (AGC) software.

The reconstruction began with reconstructed source code for Luminary 97. Changes between revisions 96 and 97 were backed out, as described by anomal report LNY-59. transcribed from a digitized copy of that program. The reconstruction was verified by matching memory-bank checksums to those listed in drawing 2021152D. Note that page numbers in the reconstructed code match those on the Luminary 099 revision 001 printout, although the added code would likely have changed page numbers for a real Luminary 96 listing.

Comments from the original source code are prefixed with a single '#' symbol, whereas comments added later are prefixed by "##" or "###". Report any errors noted by creating an issue report at the Virtual AGC project's GitHub repository.

047281,000002:                                                                                                  ## Copyright:   Public domain.
047282,000003:                                                                                                  ## Filename:    LATITUDE_LONGITUDE_SUBROUTINES.agc
047283,000004:                                                                                                  ## Purpose:     A section of Luminary revision 96.
047284,000005:                                                                                                  ##              It is part of the reconstructed source code for the
047285,000006:                                                                                                  ##              original release of the flight software for the Lunar 
047286,000007:                                                                                                  ##              Module's (LM) Apollo Guidance Computer (AGC) for Apollo 11.
047287,000008:                                                                                                  ##              The code has been recreated from a previously reconstructed
047288,000009:                                                                                                  ##              copy of Luminary 97 by undoing changes described in anomaly
047289,000010:                                                                                                  ##              report LNY-59. The code has been adapted such that the
047290,000011:                                                                                                  ##              resulting bugger words exactly match those specified for
047291,000012:                                                                                                  ##              Luminary 96 in NASA drawing 2021152D, which gives relatively
047292,000013:                                                                                                  ##              high confidence that the reconstruction is correct.
047293,000014:                                                                                                  ## Reference:   pp. 1133-1139
047294,000015:                                                                                                  ## Assembler:   yaYUL
047295,000016:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
047296,000017:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
047297,000018:                                                                                                  ## Mod history: 2019-08-04 MAS  Created from Luminary 97.
047298,000019: 

Page 1133

047300,000021:                                                                                                  #  SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047301,000022: 
047302,000023:                                                                                                  #  CALLING SEQUENCE
047303,000024:                                                                                                  #        L-1     CALL
047304,000025:                                                                                                  #        L               LAT-LONG
047305,000026: 
047306,000027:                                                                                                  #  SUBROUTINES USED
047307,000028:                                                                                                  #        R-TO-RP, ARCTAN, SETGAMMA, SETRE
047308,000029: 
047309,000030:                                                                                                  #  ERASABLE INIT. REQ.
047310,000031:                                                                                                  #        AXO, -AYO, AZO, TEPHEM (SET AT LAUNCH TIME)
047311,000032:                                                                                                  #        ALPHAV = POSITION VECTOR METERS B-29
047312,000033:                                                                                                  #        MPAC -- TIME (CSECS B-28)
047313,000034:                                                                                                  #        ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047314,000035:                                                                                                  #        LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047315,000036: 
047316,000037:                                                                                                  #  OUTPUT
047317,000038:                                                                                                  #        LATITUDE IN LAT         (REVS. B-0)
047318,000039:                                                                                                  #        LONGITUDE IN LONG       (REVS. B-0)
047319,000040:                                                                                                  #        ALTITUDE IN ALT         METERS B-29
047320,000041: 
047321,000042: 30,3775                                           BANK     30                                    
047322,000043: 13,2000                                           SETLOC   LATLONG                               
047323,000044: 13,2000                                           BANK                                           
047324,000045: 
047325,000046: 13,2351                                           COUNT*   $$/LT-LG                              
047326,000047: 13,2351  E4,1431                                  EBANK=   ALPHAV                                
047327,000048: 13,2351           40220        LAT-LONG           STQ      SETPD                                 
047328,000049: 13,2352           03674                                    INCORPEX                              
047329,000050: 13,2353           00001                                    0D                                    
047330,000051: 13,2354           24007                           STOVL    6D                                    #  SAVE TIME IN 6-7D FOR R-TO-RP
047331,000052: 13,2355           02032                                    ALPHAV                                
047332,000053: 13,2356           51406                           PUSH     ABVAL                                 #  0-5D= R FOR R-TO-RP
047333,000054: 13,2357           16070                           STODL    ALPHAM                                #  ABS. VALUE OF R FOR ALT FORMULA BELOW
047334,000055: 13,2360           24007                                    ZEROVEC                               #  SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047335,000056: 13,2361           71414                           BOFF     COS                                   #  USE COS(0) TO GET NON-ZERO IN MPAC
047336,000057: 13,2362           01743                                    LUNAFLAG                              #  0=EARTH, 1=MOON
047337,000058: 13,2363           26364                                    CALLRTRP                              
047338,000059: 13,2364           77624        CALLRTRP           CALL                                           
047339,000060: 13,2365           51670                                    R-TO-RP                               #  RP VECTOR CONVERTED FROM R B-29
047340,000061: 13,2366           77656                           UNIT                                           #  UNIT RP B-1
047341,000062: 13,2367           36032                           STCALL   ALPHAV                                #  U2= 1/2 SINL FOR SETRE SUBR BELOW
047342,000063: 13,2370           26550                                    SETGAMMA                              #        SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
047343,000064: 13,2371           77624                           CALL                                           #        SCALED B-1
047344,000065: 13,2372           26560                                    SETRE                                 #  CALC RE METERS B-29
047345,000066: 13,2373           63545                           DLOAD    DSQ                                   
047346,000067: 13,2374           02032                                    ALPHAV                                
047347,000068: 13,2375           63525                           PDDL     DSQ                                   
047348,000069: 13,2376           02034                                    ALPHAV     +2                         
047349,000070: 13,2377           75415                           DAD      SQRT                                  

Page 1134

047351,000072: 13,2400           76405                           DMP      SL1R                                  
047352,000073: 13,2401           00011                                    GAMRP                                 
047353,000074: 13,2402           14021                           STODL    COSTH                                 #  COS(LAT) B-1
047354,000075: 13,2403           02036                                    ALPHAV     +4                         
047355,000076: 13,2404           34023                           STCALL   SINTH                                 #  SIN(LAT) B-1
047356,000077: 13,2405           26510                                    ARCTAN                                
047357,000078: 13,2406           15121                           STODL    LAT                                   #  LAT B0
047358,000079: 13,2407           02032                                    ALPHAV                                
047359,000080: 13,2410           14021                           STODL    COSTH                                 #  COS(LONG) B-1
047360,000081: 13,2411           02034                                    ALPHAV     +2                         
047361,000082: 13,2412           34023                           STCALL   SINTH                                 #  SIN(LONG) B-1
047362,000083: 13,2413           26510                                    ARCTAN                                
047363,000084: 13,2414           15123                           STODL    LONG                                  #  LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047364,000085: 13,2415           02070                                    ALPHAM                                
047365,000086: 13,2416           77625                           DSU                                            #  ALT= R-RE METERS B-29
047366,000087: 13,2417           03673                                    ERADM                                 
047367,000088: 13,2420           35125                           STCALL   ALT                                   #  EXIT WITH ALT METERS B-29
047368,000089: 13,2421           03674                                    INCORPEX                              

Page 1135

047370,000091:                                                                                                  #  SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047371,000092: 
047372,000093:                                                                                                  #  CALLING SEQUENCE
047373,000094:                                                                                                  #        L-1     CALL
047374,000095:                                                                                                  #        L               LALOTORV
047375,000096: 
047376,000097:                                                                                                  #  SUBROUTINES USED
047377,000098:                                                                                                  #        SETGAMMA, SETRE, RP-TO-R
047378,000099: 
047379,000100:                                                                                                  #  ERASABLE INIT. REQ.
047380,000101:                                                                                                  #        AXO, AYO, AZO, TEPHEM SET AT LAUNCH TIME
047381,000102:                                                                                                  #        LAT -- LATITUDE         (REVS B0)
047382,000103:                                                                                                  #        LONG -- LONGITUDE       (REVS B0)
047383,000104:                                                                                                  #        ALT -- ALTITUDE         (METERS) B-29
047384,000105:                                                                                                  #        MPAC -- TIME            (CSECS B-28)
047385,000106:                                                                                                  #        ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047386,000107:                                                                                                  #        LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047387,000108: 
047388,000109:                                                                                                  #  OUTPUT
047389,000110:                                                                                                  #        R-VECTOR IN ALPHAV      (METERS B-29)
047390,000111: 
047391,000112: 13,2422           40220        LALOTORV           STQ      SETPD                                 #  LAT,LONG,ALT TO R VECTOR
047392,000113: 13,2423           03674                                    INCORPEX                              
047393,000114: 13,2424           00001                                    0D                                    
047394,000115: 13,2425           34007                           STCALL   6D                                    #  6-7D= TIME FOR RP-TO-R
047395,000116: 13,2426           26550                                    SETGAMMA                              #  GAMMA=B2/A2 FOR EARTH, 1 FOR MOON B-1
047396,000117: 13,2427           73545                           DLOAD    SIN                                   #                COS(LONG)COS(LAT) IN MPAC
047397,000118: 13,2430           01121                                    LAT                                   #      UNIT RP = SIN(LONG)COS(LAT)    2-3D
047398,000119: 13,2431           65275                           DMPR     PDDL                                  #  PD 2          GAMMA*SIN(LAT)       0-1D
047399,000120: 13,2432           00011                                    GAMRP                                 
047400,000121: 13,2433           01121                                    LAT                                   #         0-1D = GAMMA*SIN(LAT) B-2
047401,000122: 13,2434           65346                           COS      PDDL                                  #  PD4    2-3D = COS(LAT) B-1 TEMPORARILY
047402,000123: 13,2435           01123                                    LONG                                  
047403,000124: 13,2436           57356                           SIN      DMPR                                  #  PD 2
047404,000125: 13,2437           71525                           PDDL     COS                                   #  PD 4   2-3D = SIN(LONG)COS(LAT) B-2
047405,000126: 13,2440           01121                                    LAT                                   
047406,000127: 13,2441           71525                           PDDL     COS                                   #  PD 6   4-5D = COS(LAT) B-1 TEMPORARILY
047407,000128: 13,2442           01123                                    LONG                                  
047408,000129: 13,2443           55475                           DMPR     VDEF                                  #  PD 4   MPAC = COS(LONG)COS(LAT) B-2
047409,000130: 13,2444           41456                           UNIT     PUSH                                  #  0-5D= UNIT RP FOR RP-TO-R SUBR.
047410,000131: 13,2445           36032                           STCALL   ALPHAV                                #  ALPHAV +4= SINL FOR SETRE SUBR.
047411,000132: 13,2446           26560                                    SETRE                                 #  RE METERS B-29
047412,000133: 13,2447           43145                           DLOAD    BOFF                                  #  SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047413,000134: 13,2450           24007                                    ZEROVEC                               
047414,000135: 13,2451           01743                                    LUNAFLAG                              
047415,000136: 13,2452           26454                                    CALLRPRT                              
047416,000137: 13,2453           77746                           COS                                            #  USE COS(0) TO GET NON-ZERO IN MPAC
047417,000138: 13,2454           77624        CALLRPRT           CALL                                           
047418,000139: 13,2455           55716                                    RP-TO-R                               #  EXIT WITH UNIT R VECTOR IN MPAC
047419,000140: 13,2456           16032                           STODL    ALPHAV                                
047420,000141: 13,2457           03673                                    ERADM                                 

Page 1136

047422,000143: 13,2460           74215                           DAD      VXSC                                  #  (RE + ALT)(UNIT R) METERS B-30
047423,000144: 13,2461           01125                                    ALT                                   
047424,000145: 13,2462           02032                                    ALPHAV                                
047425,000146: 13,2463           77772                           VSL1                                           #  R METERS B-29
047426,000147: 13,2464           36032                           STCALL   ALPHAV                                #  EXIT WITH R IN METERS B-29
047427,000148: 13,2465           03674                                    INCORPEX                              
047428,000149: 
047429,000150:                                                                                                  #  SUBROUTINE TO COMPUTE EARTH RADIUS
047430,000151: 
047431,000152:                                                                                                  #  INPUT
047432,000153:                                                                                                  #        1/2 SIN LAT IN ALPHAV +4
047433,000154: 
047434,000155:                                                                                                  #  OUTPUT
047435,000156:                                                                                                  #        EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047436,000157: 
047437,000158: 13,2466           63545        GETERAD            DLOAD    DSQ                                   
047438,000159: 13,2467           02036                                    ALPHAV     +4                         #  SIN**2(L)
047439,000160: 13,2470           44352                           SL1      BDSU                                  
047440,000161: 13,2471           24005                                    DP1/2                                 #  COS**2(L)
047441,000162: 13,2472           44275                           DMPR     BDSU                                  
047442,000163: 13,2473           26507                                    EE                                    
047443,000164: 13,2474           24005                                    DP1/2                                 
047444,000165: 13,2475           75465                           BDDV     SQRT                                  
047445,000166: 13,2476           26503                                    B2XSC                                 
047446,000167: 13,2477           77622                           SR4R                                           
047447,000168: 13,2500           03673                           STORE    ERADM                                 
047448,000169: 13,2501           77616                           RVQ                                            
047449,000170: 
047450,000171:                                                                                                  #  THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
047451,000172:                                                                                                  #  B2XSC = B**2 SCALED B-51
047452,000173:                                                                                                  #  B2/A2 = B**2/A**2 SCALED B-1
047453,000174:                                                                                                  #  EE = (1-B**2/A**2) SCALED B-0
047454,000175: 
047455,000176: 13,2502           00446 00305  B2XSC              2DEC     .0179450689                            #  B**2 SCALED B-51
047456,000177: 13,2504  12,2004               DP1/2              =        XUNIT                                 
047457,000178: 13,2504           17711 05254  B2/A2              2DEC     .9933064884 B-1                        #  GAMMA= B**2/A**2 B-1
047458,000179: 13,2506           00155 25250  EE                 2DEC     6.6935116  E-3                        #  (1-B**2/A**2) B-0
047459,000180: 

Page 1137

047461,000182:                                                                                                  #  ARCTAN SUBROUTINE
047462,000183: 
047463,000184:                                                                                                  #  CALLING SEQUENCE
047464,000185:                                                                                                  #        SIN THETA IN SINTH B-1
047465,000186:                                                                                                  #        COS THETA IN COSTH B-1
047466,000187:                                                                                                  #        CALL ARCTAN
047467,000188: 
047468,000189:                                                                                                  #  OUTPUT
047469,000190:                                                                                                  #        ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047470,000191: 
047471,000192: 13,2510           77600        ARCTAN             BOV                                            
047472,000193: 13,2511           26512                                    CLROVFLW                              
047473,000194: 13,2512           63545        CLROVFLW           DLOAD    DSQ                                   
047474,000195: 13,2513           00023                                    SINTH                                 
047475,000196: 13,2514           63525                           PDDL     DSQ                                   
047476,000197: 13,2515           00021                                    COSTH                                 
047477,000198: 13,2516           77615                           DAD                                            
047478,000199: 13,2517           75454                           BZE      SQRT                                  
047479,000200: 13,2520           26536                                    ARCTANXX                              #  ATAN=0/0  SET THETA=0
047480,000201: 13,2521           40065                           BDDV     BOV                                   
047481,000202: 13,2522           00023                                    SINTH                                 
047482,000203: 13,2523           26543                                    ATAN=90                               
047483,000204: 13,2524           67542                           SR1      ASIN                                  
047484,000205: 13,2525           00025                           STORE    THETA                                 
047485,000206: 13,2526           50125                           PDDL     BMN                                   
047486,000207: 13,2527           00021                                    COSTH                                 
047487,000208: 13,2530           26532                                    NEGCOS                                
047488,000209: 13,2531           43545                           DLOAD    RVQ                                   
047489,000210: 13,2532           57545        NEGCOS             DLOAD    DCOMP                                 
047490,000211: 13,2533           43244                           BPL      DAD                                   
047491,000212: 13,2534           26540                                    NEGOUT                                
047492,000213: 13,2535           24005                                    DP1/2                                 
047493,000214: 13,2536           00025        ARCTANXX           STORE    THETA                                 
047494,000215: 13,2537           77616                           RVQ                                            
047495,000216: 
047496,000217: 13,2540           52025        NEGOUT             DSU      GOTO                                  
047497,000218: 13,2541           24005                                    DP1/2                                 
047498,000219: 13,2542           26536                                    ARCTANXX                              
047499,000220: 13,2543           75345        ATAN=90            DLOAD    SIGN                                  
047500,000221: 13,2544           11037                                    LODP1/4                               
047501,000222: 13,2545           00023                                    SINTH                                 
047502,000223: 13,2546           00025                           STORE    THETA                                 
047503,000224: 13,2547           77616                           RVQ                                            
047504,000225: 
047505,000226: 13,2550  12,2006               2DZERO             =        DPZERO                                
047506,000227: 

Page 1138

047508,000229:                                                                                                  #  ..... SETGAMMA SUBROUTINE .....
047509,000230:                                                                                                  #  SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047510,000231: 
047511,000232:                                                                                                  #  GAMMA = B**2/A**2 FOR EARTH (B-1)
047512,000233:                                                                                                  #  GAMMA = 1 FOR MOON (B-1)
047513,000234: 
047514,000235:                                                                                                  #  CALLING SEQUENCE
047515,000236:                                                                                                  #        L       CALL
047516,000237:                                                                                                  #        L+1             SETGAMMA
047517,000238: 
047518,000239:                                                                                                  #  INPUT
047519,000240:                                                                                                  #        LUNAFLAG=0 FOR EARTH, =1 FOR MOON
047520,000241: 
047521,000242:                                                                                                  #  OUTPUT
047522,000243:                                                                                                  #        GAMMA IN GAMRP (B-1)
047523,000244: 
047524,000245: 13,2550           43145        SETGAMMA           DLOAD    BOFF                                  #  BRANCH FOR EARTH
047525,000246: 13,2551           26505                                    B2/A2                                 #  EARTH GAMMA
047526,000247: 13,2552           01743                                    LUNAFLAG                              
047527,000248: 13,2553           26556                                    SETGMEX                               
047528,000249: 13,2554           77735                           SLOAD                                          
047529,000250: 13,2555           24005                                    1B1                                   #  MOON GAMMA
047530,000251: 13,2556           00011        SETGMEX            STORE    GAMRP                                 
047531,000252: 13,2557           77616                           RVQ                                            
047532,000253: 13,2560                        GAMRP              =        8D                                    
047533,000254: 

Page 1139

047535,000256:                                                                                                  #  ..... SETRE SUBROUTINE .....
047536,000257:                                                                                                  #  SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047537,000258: 
047538,000259:                                                                                                  #        RE = RM FOR MOON
047539,000260:                                                                                                  #        RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047540,000261: 
047541,000262:                                                                                                  #  CALLING SEQUENCE
047542,000263:                                                                                                  #        L       CALL
047543,000264:                                                                                                  #        L+1             SETRE
047544,000265: 
047545,000266:                                                                                                  #  SUBROUTINES USED
047546,000267:                                                                                                  #        GETERAD
047547,000268: 
047548,000269:                                                                                                  #  INPUT
047549,000270:                                                                                                  #        ERADFLAG = 0 FOR FIXED RE, 1 FOR COMPUTED RE
047550,000271:                                                                                                  #        ALPHAV +4 = 1/2 SINL IF GETERAD IS CALLED
047551,000272:                                                                                                  #        LUNAFLAG = 0 FOR EARTH, =1 FOR MOON
047552,000273: 
047553,000274:                                                                                                  #  OUTPUT
047554,000275:                                                                                                  #        ERADM = 504RM FOR MOON (METERS B-29)
047555,000276:                                                                                                  #        ERADM = ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047556,000277: 
047557,000278: 13,2560           71220        SETRE              STQ      DLOAD                                 
047558,000279: 13,2561           00051                                    SETREX                                
047559,000280: 13,2562           10003                                    504RM                                 
047560,000281: 13,2563           71214                           BON      DLOAD                                 #  BRANCH FOR MOON
047561,000282: 13,2564           01703                                    LUNAFLAG                              
047562,000283: 13,2565           26575                                    TSTRLSRM                              
047563,000284: 13,2566           10001                                    ERAD                                  
047564,000285: 13,2567           45014                           BOFF     CALL                                  #  ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
047565,000286: 13,2570           00742                                    ERADFLAG                              
047566,000287: 13,2571           26573                                    SETRXX                                
047567,000288: 13,2572           26466                                    GETERAD                               
047568,000289: 13,2573           37673        SETRXX             STCALL   ERADM                                 #  EXIT WITH RE OR RM METERS B-29
047569,000290: 13,2574           00051                                    SETREX                                
047570,000291: 13,2575           77214        TSTRLSRM           BON      VLOAD                                 #  ERADFLAG=0, SET R0=RLS
047571,000292: 13,2576           00702                                    ERADFLAG                              #          =1      R0=RM
047572,000293: 13,2577           26573                                    SETRXX                                
047573,000294: 13,2600           02023                                    RLS                                   
047574,000295: 13,2601           64446                           ABVAL    SR2R                                  #  SCALE FROM B-27 TO B-29
047575,000296: 13,2602           77650                           GOTO                                           
047576,000297: 13,2603           26573                                    SETRXX                                
047577,000298: 13,2604  0000051               SETREX             =        S2                                    
047578,000299: 
047579,000300: 

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