Source Code

These source-code files derive from a printout of Luminary 116 (the Apollo 12 Lunar Module guidance computer program), from the personal library of original AGC developer Don Eyles, digitally photographed at archive.org, financially sponsored by Ron Burkey, and transcribed to source code by a team of volunteers. This colorized, syntax-highlighted form was created by assembling that transcribed source code. Note that the full page images are available on the Virtual AGC project page at archive.org, while reduced-size images are presented at the VirtualAGC project website. Report or fix any transcription errors at the Virtual AGC project code repository.

Notations on the program listing read, in part:

	GAP:  ASSEMBLE REVISION 116 OF AGC PROGRAM LUMINARY BY NASA 2021112-071
	19:09 AUG. 11,1969
Note that the date is the date of the printout, not the date of the program revision.

047500,000002:                                                                                                  ## Copyright:   Public domain.
047501,000003:                                                                                                  ## Filename:    LATITUDE_LONGITUDE_SUBROUTINES.agc
047502,000004:                                                                                                  ## Purpose:     A section of Luminary revision 116.
047503,000005:                                                                                                  ##              It is part of the source code for the Lunar Module's (LM) 
047504,000006:                                                                                                  ##              Apollo Guidance Computer (AGC) for Apollo 12.
047505,000007:                                                                                                  ##              This file is intended to be a faithful transcription, except
047506,000008:                                                                                                  ##              that the code format has been changed to conform to the
047507,000009:                                                                                                  ##              requirements of the yaYUL assembler rather than the
047508,000010:                                                                                                  ##              original YUL assembler.
047509,000011:                                                                                                  ## Reference:   pp. 1125-1131
047510,000012:                                                                                                  ## Assembler:   yaYUL
047511,000013:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
047512,000014:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
047513,000015:                                                                                                  ## Mod history: 2017-01-22 MAS  Created from Luminary 99.
047514,000016:                                                                                                  ##              2017-01-28 RRB  Updated for Luminary 116.
047515,000017:                                                                                                  ##              2017-03-13 RSB  Proofed comment text via 3-way diff vs
047516,000018:                                                                                                  ##                              Luminary 99 and 131 ... no problems found.
047517,000019:                                                                                                  ##              2017-03-15 RSB  Comment-text fixes identified in 5-way
047518,000020:                                                                                                  ##                              side-by-side diff of Luminary 69/99/116/131/210.
047519,000021: 

Page 1125

047521,000023:                                                                                                  #  SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047522,000024: 
047523,000025:                                                                                                  #  CALLING SEQUENCE
047524,000026: 
047525,000027:                                                                                                  #    L-1    CALL
047526,000028:                                                                                                  #    L             LAT-LONG
047527,000029:                                                                                                  #  SUBROUTINES USED
047528,000030: 
047529,000031:                                                                                                  #   R-TO-RP,ARCTAN,SETGAMMA,SETRE
047530,000032:                                                                                                  #  ERASABLE INIT. REQ.
047531,000033: 
047532,000034:                                                                                                  #    AXO,-AYO,AZO,TEPHEM (SET AT LAUNCH TIME)
047533,000035:                                                                                                  #  ALPHAV = POSITION VECTOR METERS B-29
047534,000036:                                                                                                  #    MPAC-- TIME  (CSECS B-28)
047535,000037:                                                                                                  #   ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047536,000038:                                                                                                  #   LUNAFLAG=0 FOR EARTH,1 FOR MOON
047537,000039:                                                                                                  #  OUTPUT
047538,000040: 
047539,000041:                                                                                                  #    LATITUDE IN LAT    (REVS. B-0)
047540,000042:                                                                                                  #    LONGITUDE IN LONG   (REVS. B-0)
047541,000043:                                                                                                  #  ALTITUDE IN ALT METERS B-29
047542,000044: 
047543,000045: 30,3762                                           BANK     30                                    
047544,000046: 13,2000                                           SETLOC   LATLONG                               
047545,000047: 13,2000                                           BANK                                           
047546,000048: 
047547,000049: 13,2351                                           COUNT*   $$/LT-LG                              
047548,000050: 13,2351  E4,1431                                  EBANK=   ALPHAV                                
047549,000051: 13,2351           40220        LAT-LONG           STQ      SETPD                                 
047550,000052: 13,2352           03674                                    INCORPEX                              
047551,000053: 13,2353           00001                                    0D                                    
047552,000054: 13,2354           24007                           STOVL    6D                                    #  SAVE TIME IN 6-7D FOR R-TO-RP
047553,000055: 13,2355           02032                                    ALPHAV                                
047554,000056: 13,2356           51406                           PUSH     ABVAL                                 #  0-5D= R FOR R-TO-RP
047555,000057: 13,2357           16070                           STODL    ALPHAM                                #  ABS. VALUE OF R FOR ALT FORMULA BELOW
047556,000058: 13,2360           24007                                    ZEROVEC                               #  SET MPAC=0 FOR EARTH, NON-ZERO FOR MOON
047557,000059: 13,2361           71414                           BOFF     COS                                   #  USE COS(0) TO GET NON-ZERO IN MPAC
047558,000060: 13,2362           01743                                    LUNAFLAG                              #  0=EARTH, 1=MOON
047559,000061: 13,2363           26364                                    CALLRTRP                              
047560,000062: 13,2364           77624        CALLRTRP           CALL                                           
047561,000063: 13,2365           51677                                    R-TO-RP                               #  RP VECTOR CONVERTED FROM R B-29
047562,000064: 13,2366           77656                           UNIT                                           #  UNIT RP B-1
047563,000065: 13,2367           36032                           STCALL   ALPHAV                                #  U2= 1/2 SINL FOR SETRE SUBR BELOW
047564,000066: 13,2370           26550                                    SETGAMMA                              #   SET GAMMA=B2/A2 FOR EARTH, =1 FOR MOON
047565,000067: 13,2371           77624                           CALL                                           #   SCALED B-1
047566,000068: 13,2372           26560                                    SETRE                                 #  CALC RE METERS B-29
047567,000069: 13,2373           63545                           DLOAD    DSQ                                   
047568,000070: 13,2374           02032                                    ALPHAV                                
047569,000071: 13,2375           63525                           PDDL     DSQ                                   
047570,000072: 13,2376           02034                                    ALPHAV     +2                         
047571,000073: 13,2377           75415                           DAD      SQRT                                  

Page 1126

047573,000075: 13,2400           76405                           DMP      SL1R                                  
047574,000076: 13,2401           00011                                    GAMRP                                 
047575,000077: 13,2402           14021                           STODL    COSTH                                 #  COS(LAT) B-1
047576,000078: 13,2403           02036                                    ALPHAV     +4                         
047577,000079: 13,2404           34023                           STCALL   SINTH                                 #  SIN(LAT) B-1
047578,000080: 13,2405           26510                                    ARCTAN                                
047579,000081: 13,2406           15120                           STODL    LAT                                   #  LAT B0
047580,000082: 13,2407           02032                                    ALPHAV                                
047581,000083: 13,2410           14021                           STODL    COSTH                                 #  COS(LONG) B-1
047582,000084: 13,2411           02034                                    ALPHAV     +2                         
047583,000085: 13,2412           34023                           STCALL   SINTH                                 #  SIN(LONG) B-1
047584,000086: 13,2413           26510                                    ARCTAN                                
047585,000087: 13,2414           15122                           STODL    LONG                                  #  LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047586,000088: 13,2415           02070                                    ALPHAM                                
047587,000089: 13,2416           77625                           DSU                                            #  ALT= R-RE METERS B-29
047588,000090: 13,2417           03673                                    ERADM                                 
047589,000091: 13,2420           35124                           STCALL   ALT                                   #  EXIT WITH ALT METERS B-29
047590,000092: 13,2421           03674                                    INCORPEX                              

Page 1127

047592,000094:                                                                                                  #  SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047593,000095: 
047594,000096:                                                                                                  #  CALLING SEQUENCE
047595,000097: 
047596,000098:                                                                                                  #    L-1    CALL
047597,000099:                                                                                                  #    L             LALOTORV
047598,000100:                                                                                                  #  SUBROUTINES USED
047599,000101: 
047600,000102:                                                                                                  #   SETGAMMA,SETRE,RP-TO-R
047601,000103:                                                                                                  #  ERASABLE INIT. REQ.
047602,000104: 
047603,000105:                                                                                                  #    AXO,AYO,AZO,TEPHEM SET AT LAUNCH TIME
047604,000106:                                                                                                  #    LAT-- LATITUDE  (REVS B0)
047605,000107:                                                                                                  #    LONG-- LONGITUDE  (REVS B0)
047606,000108:                                                                                                  #  ALT--ALTITUDE (METERS) B-29
047607,000109:                                                                                                  #    MPAC-- TIME  (CSECS B-28)
047608,000110:                                                                                                  #    ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047609,000111:                                                                                                  #   LUNAFLAG=0 FOR EARTH, 1 FOR MOON
047610,000112: 
047611,000113:                                                                                                  #  OUTPUT
047612,000114: 
047613,000115:                                                                                                  #  R-VECTOR IN ALPHAV (METERS B-29)
047614,000116: 
047615,000117: 13,2422           40220        LALOTORV           STQ      SETPD                                 #  LAT,LONG,ALT TO R VECTOR
047616,000118: 13,2423           03674                                    INCORPEX                              
047617,000119: 13,2424           00001                                    0D                                    
047618,000120: 13,2425           34007                           STCALL   6D                                    #  6-7D= TIME FOR RP-TO-R
047619,000121: 13,2426           26550                                    SETGAMMA                              #  GAMMA=B2/A2 FOR EARTH, 1 FOR MOON B-1
047620,000122: 13,2427           73545                           DLOAD    SIN                                   #                COS(LONG)COS(LAT) IN MPAC
047621,000123: 13,2430           01120                                    LAT                                   #       UNIT RP= SIN(LONG)COS(LAT)    2-3D
047622,000124: 13,2431           65275                           DMPR     PDDL                                  #  PD 2          GAMMA*SIN(LAT)       0-1D
047623,000125: 13,2432           00011                                    GAMRP                                 
047624,000126: 13,2433           01120                                    LAT                                   #          0-1D= GAMMA*SIN(LAT) B-2
047625,000127: 13,2434           65346                           COS      PDDL                                  #  PD4      2-3D=COS(LAT) B-1 TEMPORARILY
047626,000128: 13,2435           01122                                    LONG                                  
047627,000129: 13,2436           57356                           SIN      DMPR                                  #  PD 2
047628,000130: 13,2437           71525                           PDDL     COS                                   #  PD 4    2-3D=SIN(LONG)COS(LAT) B-2
047629,000131: 13,2440           01120                                    LAT                                   
047630,000132: 13,2441           71525                           PDDL     COS                                   #  PD 6     4-5D=COS(LAT) B-1 TEMPORARILY
047631,000133: 13,2442           01122                                    LONG                                  
047632,000134: 13,2443           55475                           DMPR     VDEF                                  #  PD 4    MPAC= COS(LONG)COS(LAT) B-2
047633,000135: 13,2444           41456                           UNIT     PUSH                                  #  0-5D= UNIT RP FOR RP-TO-R SUBR.
047634,000136: 13,2445           36032                           STCALL   ALPHAV                                #  ALPHAV +4= SINL FOR SETRE SUBR.
047635,000137: 13,2446           26560                                    SETRE                                 #  RE METERS B-29
047636,000138: 13,2447           43145                           DLOAD    BOFF                                  #  SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047637,000139: 13,2450           24007                                    ZEROVEC                               
047638,000140: 13,2451           01743                                    LUNAFLAG                              
047639,000141: 13,2452           26454                                    CALLRPRT                              
047640,000142: 13,2453           77746                           COS                                            #  USE COS(0) TO GET NON-ZERO IN MPAC
047641,000143: 13,2454           77624        CALLRPRT           CALL                                           
047642,000144: 13,2455           55716                                    RP-TO-R                               #  EXIT WITH UNIT R VECTOR IN MPAC
047643,000145: 13,2456           16032                           STODL    ALPHAV                                
047644,000146: 13,2457           03673                                    ERADM                                 

Page 1128

047646,000148: 13,2460           74215                           DAD      VXSC                                  #  (RE + ALT)(UNIT R) METERS B-30
047647,000149: 13,2461           01124                                    ALT                                   
047648,000150: 13,2462           02032                                    ALPHAV                                
047649,000151: 13,2463           77772                           VSL1                                           #  R METERS B-29
047650,000152: 13,2464           36032                           STCALL   ALPHAV                                #  EXIT WITH R IN METERS B-29
047651,000153: 13,2465           03674                                    INCORPEX                              
047652,000154: 
047653,000155:                                                                                                  #  SUBROUTINE TO COMPUTE EARTH RADIUS
047654,000156: 
047655,000157:                                                                                                  #  INPUT
047656,000158: 
047657,000159:                                                                                                  #    1/2 SIN LAT IN ALPHAV +4
047658,000160: 
047659,000161:                                                                                                  #  OUTPUT
047660,000162: 
047661,000163:                                                                                                  #    EARTH RADIUS IN ERADM AND MPAC (METERS B-29)
047662,000164: 
047663,000165: 13,2466           63545        GETERAD            DLOAD    DSQ                                   
047664,000166: 13,2467           02036                                    ALPHAV     +4                         #  SIN**2(L)
047665,000167: 13,2470           44352                           SL1      BDSU                                  
047666,000168: 13,2471           24005                                    DP1/2                                 #  COS**2(L)
047667,000169: 13,2472           44275                           DMPR     BDSU                                  
047668,000170: 13,2473           26507                                    EE                                    
047669,000171: 13,2474           24005                                    DP1/2                                 
047670,000172: 13,2475           75465                           BDDV     SQRT                                  
047671,000173: 13,2476           26503                                    B2XSC                                 
047672,000174: 13,2477           77622                           SR4R                                           
047673,000175: 13,2500           03673                           STORE    ERADM                                 
047674,000176: 13,2501           77616                           RVQ                                            
047675,000177: 
047676,000178:                                                                                                  #  THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166, B=6356784 METERS
047677,000179:                                                                                                  #  B2XSC = B**2 SCALED B-51
047678,000180:                                                                                                  #  B2/A2 = B**2/A**2 SCALED B-1
047679,000181:                                                                                                  #  EE = (1-B**2/A**2) SCALED B-0
047680,000182: 
047681,000183: 13,2502           00446 00305  B2XSC              2DEC     .0179450689                            #  B**2 SCALED B-51
047682,000184: 13,2504  12,2004               DP1/2              =        XUNIT                                 
047683,000185: 13,2504           17711 05254  B2/A2              2DEC     .9933064884 B-1                        #  GAMMA= B**2/A**2 B-1
047684,000186: 13,2506           00155 25250  EE                 2DEC     6.6935116  E-3                        #  (1-B**2/A**2) B-0
047685,000187: 

Page 1129

047687,000189:                                                                                                  #  ARCTAN SUBROUTINE
047688,000190: 
047689,000191:                                                                                                  #  CALLING SEQUENCE
047690,000192: 
047691,000193:                                                                                                  #    SIN THETA IN SINTH B-1
047692,000194:                                                                                                  #    COS THETA IN COSTH B-1
047693,000195:                                                                                                  #    CALL ARCTAN
047694,000196: 
047695,000197:                                                                                                  #  OUTPUT
047696,000198:                                                                                                  #    ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047697,000199: 
047698,000200: 13,2510           77600        ARCTAN             BOV                                            
047699,000201: 13,2511           26512                                    CLROVFLW                              
047700,000202: 13,2512           63545        CLROVFLW           DLOAD    DSQ                                   
047701,000203: 13,2513           00023                                    SINTH                                 
047702,000204: 13,2514           63525                           PDDL     DSQ                                   
047703,000205: 13,2515           00021                                    COSTH                                 
047704,000206: 13,2516           77615                           DAD                                            
047705,000207: 13,2517           75454                           BZE      SQRT                                  
047706,000208: 13,2520           26536                                    ARCTANXX                              #  ATAN=0/0  SET THETA=0
047707,000209: 13,2521           40065                           BDDV     BOV                                   
047708,000210: 13,2522           00023                                    SINTH                                 
047709,000211: 13,2523           26543                                    ATAN=90                               
047710,000212: 13,2524           67542                           SR1      ASIN                                  
047711,000213: 13,2525           00025                           STORE    THETA                                 
047712,000214: 13,2526           50125                           PDDL     BMN                                   
047713,000215: 13,2527           00021                                    COSTH                                 
047714,000216: 13,2530           26532                                    NEGCOS                                
047715,000217: 13,2531           43545                           DLOAD    RVQ                                   
047716,000218: 13,2532           57545        NEGCOS             DLOAD    DCOMP                                 
047717,000219: 13,2533           43244                           BPL      DAD                                   
047718,000220: 13,2534           26540                                    NEGOUT                                
047719,000221: 13,2535           24005                                    DP1/2                                 
047720,000222: 13,2536           00025        ARCTANXX           STORE    THETA                                 
047721,000223: 13,2537           77616                           RVQ                                            
047722,000224: 
047723,000225: 13,2540           52025        NEGOUT             DSU      GOTO                                  
047724,000226: 13,2541           24005                                    DP1/2                                 
047725,000227: 13,2542           26536                                    ARCTANXX                              
047726,000228: 13,2543           75345        ATAN=90            DLOAD    SIGN                                  
047727,000229: 13,2544           11021                                    LODP1/4                               
047728,000230: 13,2545           00023                                    SINTH                                 
047729,000231: 13,2546           00025                           STORE    THETA                                 
047730,000232: 13,2547           77616                           RVQ                                            
047731,000233: 
047732,000234: 13,2550  12,2006               2DZERO             =        DPZERO                                
047733,000235: 

Page 1130

047735,000237:                                                                                                  #  ..... SETGAMMA SUBROUTINE .....
047736,000238:                                                                                                  #  SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047737,000239: 
047738,000240:                                                                                                  #   GAMMA = B**2/A**2 FOR EARTH (B-1)
047739,000241:                                                                                                  #   GAMMA = 1 FOR MOON (B-1)
047740,000242: 
047741,000243:                                                                                                  #  CALLING SEQUENCE
047742,000244:                                                                                                  #   L       CALL
047743,000245:                                                                                                  #   L+1            SETGAMMA
047744,000246: 
047745,000247:                                                                                                  #  INPUT
047746,000248:                                                                                                  #   LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047747,000249: 
047748,000250:                                                                                                  #  OUTPUT
047749,000251:                                                                                                  #    GAMMA IN GAMRP (B-1)
047750,000252: 
047751,000253: 13,2550           43145        SETGAMMA           DLOAD    BOFF                                  #  BRANCH FOR EARTH
047752,000254: 13,2551           26505                                    B2/A2                                 #  EARTH GAMMA
047753,000255: 13,2552           01743                                    LUNAFLAG                              
047754,000256: 13,2553           26556                                    SETGMEX                               
047755,000257: 13,2554           77735                           SLOAD                                          
047756,000258: 13,2555           24005                                    1B1                                   #  MOON GAMMA
047757,000259: 13,2556           00011        SETGMEX            STORE    GAMRP                                 
047758,000260: 13,2557           77616                           RVQ                                            
047759,000261: 13,2560                        GAMRP              =        8D                                    
047760,000262: 

Page 1131

047762,000264:                                                                                                  #  ..... SETRE SUBROUTINE .....
047763,000265:                                                                                                  #  SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047764,000266: 
047765,000267:                                                                                                  #  RE = RM FOR MOON
047766,000268:                                                                                                  #   RE = RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047767,000269: 
047768,000270:                                                                                                  #  CALLING SEQUENCE
047769,000271:                                                                                                  #   L       CALL
047770,000272:                                                                                                  #   L+1            SETRE
047771,000273: 
047772,000274:                                                                                                  #  SUBROUTINES USED
047773,000275:                                                                                                  #   GETERAD
047774,000276: 
047775,000277:                                                                                                  #  INPUT
047776,000278:                                                                                                  #   ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED RE
047777,000279:                                                                                                  #   ALPHAV +4= 1/2 SINL IF GETERAD IS CALLED
047778,000280:                                                                                                  #   LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047779,000281: 
047780,000282:                                                                                                  #  OUTPUT
047781,000283:                                                                                                  #   ERADM= 504RM FOR MOON (METERS B-29)
047782,000284:                                                                                                  #   ERADM= ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047783,000285: 
047784,000286: 13,2560           71220        SETRE              STQ      DLOAD                                 
047785,000287: 13,2561           00051                                    SETREX                                
047786,000288: 13,2562           10003                                    504RM                                 
047787,000289: 13,2563           71214                           BON      DLOAD                                 #  BRANCH FOR MOON
047788,000290: 13,2564           01703                                    LUNAFLAG                              
047789,000291: 13,2565           26575                                    TSTRLSRM                              
047790,000292: 13,2566           10001                                    ERAD                                  
047791,000293: 13,2567           45014                           BOFF     CALL                                  #  ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED
047792,000294: 13,2570           00742                                    ERADFLAG                              
047793,000295: 13,2571           26573                                    SETRXX                                
047794,000296: 13,2572           26466                                    GETERAD                               
047795,000297: 13,2573           37673        SETRXX             STCALL   ERADM                                 #  EXIT WITH RE OR RM METERS B-29
047796,000298: 13,2574           00051                                    SETREX                                
047797,000299: 13,2575           77214        TSTRLSRM           BON      VLOAD                                 #  ERADFLAG=0,SET R0=RLS
047798,000300: 13,2576           00702                                    ERADFLAG                              #          =1     R0=RM
047799,000301: 13,2577           26573                                    SETRXX                                
047800,000302: 13,2600           02023                                    RLS                                   
047801,000303: 13,2601           64446                           ABVAL    SR2R                                  #  SCALE FROM B-27 TO B-29
047802,000304: 13,2602           77650                           GOTO                                           
047803,000305: 13,2603           26573                                    SETRXX                                
047804,000306: 13,2604  0000051               SETREX             =        S2                                    
047805,000307: 
047806,000308: 

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