Source Code

These source-code files are part of a reconstructed copy of Luminary 173, the second (unflown) release of the Apollo 14 Lunar Module (LM) Apollo Guidance Computer (AGC) software.

The reconstruction began with reconstructed source code for Luminary 178. Changes between revision 173 and 178 were backed out, as described by Luminary memo 167 (revision 1). The reconstruction was verified by matching memory-bank checksums to those listed in drawing 2021152N. Note that page numbers in the reconstructed code match those for the baseline log section mentioned in each file's changelog; the page numbers for a real Luminary 173 listing would be different.

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.

047644,000002:                                                                                                  ## Copyright:   Public domain.
047645,000003:                                                                                                  ## Filename:    LATITUDE_LONGITUDE_SUBROUTINES.agc
047646,000004:                                                                                                  ## Purpose:     A section of Luminary revision 173.
047647,000005:                                                                                                  ##              It is part of the reconstructed source code for the second
047648,000006:                                                                                                  ##              (unflown) release of the flight software for the Lunar
047649,000007:                                                                                                  ##              Module's (LM) Apollo Guidance Computer (AGC) for Apollo 14.
047650,000008:                                                                                                  ##              The code has been recreated from a reconstructed copy of
047651,000009:                                                                                                  ##              Luminary 178, as well as Luminary memo 167 (revision 1).
047652,000010:                                                                                                  ##              It has been adapted such that the resulting bugger words
047653,000011:                                                                                                  ##              exactly match those specified for Luminary 173 in NASA
047654,000012:                                                                                                  ##              drawing 2021152N, which gives relatively high confidence
047655,000013:                                                                                                  ##              that the reconstruction is correct.
047656,000014:                                                                                                  ## Reference:   pp. 1124-1130
047657,000015:                                                                                                  ## Assembler:   yaYUL
047658,000016:                                                                                                  ## Contact:     Ron Burkey <info@sandroid.org>.
047659,000017:                                                                                                  ## Website:     www.ibiblio.org/apollo/index.html
047660,000018:                                                                                                  ## Mod history: 2019-09-18 MAS  Created from Luminary 178.
047661,000019: 

Page 1124

047663,000021:                                                                                                  #  SUBROUTINE TO CONVERT RAD VECTOR AT GIVEN TIME TO LAT,LONG AND ALT
047664,000022: 
047665,000023:                                                                                                  #  CALLING SEQUENCE
047666,000024: 
047667,000025:                                                                                                  #    L-1    CALL
047668,000026:                                                                                                  #    L             LAT-LONG
047669,000027:                                                                                                  #  SUBROUTINES USED
047670,000028: 
047671,000029:                                                                                                  #   R-TO-RP,ARCTAN,SETGAMMA,SETRE
047672,000030:                                                                                                  #  ERASABLE INIT. REQ.
047673,000031: 
047674,000032:                                                                                                  #    AXO,-AYO,AZO,TEPHEM (SET AT LAUNCH TIME)
047675,000033:                                                                                                  #  ALPHAV = POSITION VECTOR METERS B-29
047676,000034:                                                                                                  #    MPAC-- TIME  (CSECS B-28)
047677,000035:                                                                                                  #   ERADFLAG =1, TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047678,000036:                                                                                                  #   LUNAFLAG=0 FOR EARTH,1 FOR MOON
047679,000037:                                                                                                  #  OUTPUT
047680,000038: 
047681,000039:                                                                                                  #    LATITUDE IN LAT   (REVS. B-0)
047682,000040:                                                                                                  #    LONGITUDE IN LONG   (REVS. B-0)
047683,000041:                                                                                                  #  ALTITUDE IN ALT METERS B-29
047684,000042: 30,3760                                           BANK     30                                    
047685,000043: 13,2000                                           SETLOC   LATLONG                               
047686,000044: 13,2000                                           BANK                                           
047687,000045: 
047688,000046: 13,2347                                           COUNT*   $$/LT-LG                              
047689,000047: 13,2347  E4,1431                                  EBANK=   ALPHAV                                
047690,000048: 13,2347           40220        LAT-LONG           STQ      SETPD                                 
047691,000049: 13,2350           03674                                    INCORPEX                              
047692,000050: 13,2351           00001                                    0D                                    
047693,000051: 13,2352           24007                           STOVL    6D                                    #  SAVE TIME IN 6-7D FOR R-TO-RP
047694,000052: 13,2353           02032                                    ALPHAV                                
047695,000053: 13,2354           51406                           PUSH     ABVAL                                 #  0-5D= R FOR R-TO-RP
047696,000054: 13,2355           16070                           STODL    ALPHAM                                #  ABS. VALUE OF R FOR ALT FORMULA BELOW
047697,000055: 13,2356           24007                                    ZEROVEC                               #  SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047698,000056: 13,2357           71414                           BOFF     COS                                   #  USE COS(0) TO GET NON-ZERO IN MPAC
047699,000057: 13,2360           01743                                    LUNAFLAG                              #  0=EARTH,1=MOON
047700,000058: 13,2361           26362                                    CALLRTRP                              
047701,000059: 13,2362           77624        CALLRTRP           CALL                                           
047702,000060: 13,2363           51642                                    R-TO-RP                               #  RP VECTOR CONVERTED FROM R B-29
047703,000061: 13,2364           77656                           UNIT                                           #  UNIT RP B-1
047704,000062: 13,2365           36032                           STCALL   ALPHAV                                #  U2= 1/2 SINL FOR SETRE SUBR BELOW
047705,000063: 13,2366           26546                                    SETGAMMA                              #   SET GAMMA=B2/A2 FOR EARTH,=1 FOR MOON
047706,000064: 13,2367           77624                           CALL                                           #   SCALED B-1
047707,000065: 13,2370           26556                                    SETRE                                 #  CALC RE METERS B-29
047708,000066: 13,2371           63545                           DLOAD    DSQ                                   
047709,000067: 13,2372           02032                                    ALPHAV                                
047710,000068: 13,2373           63525                           PDDL     DSQ                                   
047711,000069: 13,2374           02034                                    ALPHAV     +2                         
047712,000070: 13,2375           75415                           DAD      SQRT                                  

Page 1125

047714,000072: 13,2376           76405                           DMP      SL1R                                  
047715,000073: 13,2377           00011                                    GAMRP                                 
047716,000074: 13,2400           14021                           STODL    COSTH                                 #  COS(LAT) B-1
047717,000075: 13,2401           02036                                    ALPHAV     +4                         
047718,000076: 13,2402           34023                           STCALL   SINTH                                 #  SIN(LAT) B-1
047719,000077: 13,2403           26506                                    ARCTAN                                
047720,000078: 13,2404           15120                           STODL    LAT                                   #  LAT B0
047721,000079: 13,2405           02032                                    ALPHAV                                
047722,000080: 13,2406           14021                           STODL    COSTH                                 #  COS(LONG) B-1
047723,000081: 13,2407           02034                                    ALPHAV     +2                         
047724,000082: 13,2410           34023                           STCALL   SINTH                                 #  SIN(LONG) B-1
047725,000083: 13,2411           26506                                    ARCTAN                                
047726,000084: 13,2412           15122                           STODL    LONG                                  #  LONG. REVS B-0 IN RANGE -1/2 TO 1/2
047727,000085: 13,2413           02070                                    ALPHAM                                
047728,000086: 13,2414           77625                           DSU                                            #  ALT= R-RE METERS B-29
047729,000087: 13,2415           03673                                    ERADM                                 
047730,000088: 13,2416           35124                           STCALL   ALT                                   #  EXIT WITH ALT METERS B-29
047731,000089: 13,2417           03674                                    INCORPEX                              
047732,000090: 

Page 1126

047734,000092:                                                                                                  #  SUBROUTINE TO CONVERT LAT,LONG,ALT AT GIVEN TIME TO RADIUS VECTOR
047735,000093:                                                                                                  #  CALLING SEQUENCE
047736,000094: 
047737,000095:                                                                                                  #    L-1    CALL
047738,000096:                                                                                                  #    L             LALOTORV
047739,000097:                                                                                                  #  SUBROUTINES USED
047740,000098: 
047741,000099:                                                                                                  #   SETGAMMA,SETRE,RP-TO-R
047742,000100:                                                                                                  #  ERASABLE INIT. REQ.
047743,000101: 
047744,000102:                                                                                                  #    AXO,AYO,AZO,TEPHEM  SET AT LAUNCH TIME
047745,000103:                                                                                                  #    LAT-- LATITUDE  (REVS B0)
047746,000104:                                                                                                  #    LONG-- LONGITUDE  (REVS B0)
047747,000105:                                                                                                  #  ALT--ALTITUDE (METERS) B-29
047748,000106:                                                                                                  #    MPAC-- TIME  (CSECS B-28)
047749,000107:                                                                                                  #    ERADFLAG =1 TO COMPUTE EARTH RADIUS, =0 FOR FIXED EARTH RADIUS
047750,000108:                                                                                                  #   LUNAFLAG=0 FOR EARTH,1 FOR MOON
047751,000109:                                                                                                  #  OUTPUT
047752,000110: 
047753,000111:                                                                                                  #  R-VECTOR IN ALPHAV (METERS B-29)
047754,000112: 13,2420           40220        LALOTORV           STQ      SETPD                                 #  LAT,LONG,ALT TO R VECTOR
047755,000113: 13,2421           03674                                    INCORPEX                              
047756,000114: 13,2422           00001                                    0D                                    
047757,000115: 13,2423           34007                           STCALL   6D                                    #  6-7D= TIME FOR RP-TO-R
047758,000116: 13,2424           26546                                    SETGAMMA                              #  GAMMA=B2/A2 FOR EARTH,1 FOR MOON B-1
047759,000117: 13,2425           73545                           DLOAD    SIN                                   #                COS(LONG)COS(LAT) IN MPAC
047760,000118: 13,2426           01120                                    LAT                                   #       UNIT RP= SIN(LONG)COS(LAT)    2-3D
047761,000119: 13,2427           65275                           DMPR     PDDL                                  #  PD 2          GAMMA*SIN(LAT)       0-1D
047762,000120: 13,2430           00011                                    GAMRP                                 
047763,000121: 13,2431           01120                                    LAT                                   #          0-1D= GAMMA*SIN(LAT) B-2
047764,000122: 13,2432           65346                           COS      PDDL                                  #  PD4      2-3D=COS(LAT) B-1 TEMPORARILY
047765,000123: 13,2433           01122                                    LONG                                  
047766,000124: 13,2434           57356                           SIN      DMPR                                  #  PD 2
047767,000125: 13,2435           71525                           PDDL     COS                                   #  PD 4    2-3D=SIN(LONG)COS(LAT) B-2
047768,000126: 13,2436           01120                                    LAT                                   
047769,000127: 13,2437           71525                           PDDL     COS                                   #  PD 6     4-5D=COS(LAT) B-1 TEMPORARILY
047770,000128: 13,2440           01122                                    LONG                                  
047771,000129: 13,2441           55475                           DMPR     VDEF                                  #  PD 4    MPAC= COS(LONG)COS(LAT) B-2
047772,000130: 13,2442           41456                           UNIT     PUSH                                  #  0-5D= UNIT RP FOR RP-TO-R SUBR.
047773,000131: 13,2443           36032                           STCALL   ALPHAV                                #  ALPHAV +4= SINL FOR SETRE SUBR.
047774,000132: 13,2444           26556                                    SETRE                                 #  RE METERS B-29
047775,000133: 13,2445           43145                           DLOAD    BOFF                                  #  SET MPAC=0 FOR EARTH,NON-ZERO FOR MOON
047776,000134: 13,2446           24007                                    ZEROVEC                               
047777,000135: 13,2447           01743                                    LUNAFLAG                              
047778,000136: 13,2450           26452                                    CALLRPRT                              
047779,000137: 13,2451           77746                           COS                                            #  USE COS(0) TO GET NON-ZERO IN MPAC
047780,000138: 13,2452           77624        CALLRPRT           CALL                                           
047781,000139: 13,2453           55720                                    RP-TO-R                               #  EXIT WITH UNIT R VECTOR IN MPAC
047782,000140: 13,2454           16032                           STODL    ALPHAV                                
047783,000141: 13,2455           03673                                    ERADM                                 

Page 1127

047785,000143: 13,2456           74215                           DAD      VXSC                                  #  (RE + ALT)(UNIT R) METERS B-30
047786,000144: 13,2457           01124                                    ALT                                   
047787,000145: 13,2460           02032                                    ALPHAV                                
047788,000146: 13,2461           77772                           VSL1                                           #  R METERS B-29
047789,000147: 13,2462           36032                           STCALL   ALPHAV                                #  EXIT WITH R IN METERS B-29
047790,000148: 13,2463           03674                                    INCORPEX                              
047791,000149:                                                                                                  #  SUBROUTINE TO COMPUTE EARTH RADIUS
047792,000150: 
047793,000151:                                                                                                  #  INPUT
047794,000152: 
047795,000153:                                                                                                  #    1/2 SIN LAT IN ALPHAV +4
047796,000154: 
047797,000155:                                                                                                  #  OUTPUT
047798,000156: 
047799,000157:                                                                                                  #    EARTH RADIUS IN ERADM AND MPAC  (METERS B-29)
047800,000158: 
047801,000159: 13,2464           63545        GETERAD            DLOAD    DSQ                                   
047802,000160: 13,2465           02036                                    ALPHAV     +4                         #  SIN**2(L)
047803,000161: 13,2466           44352                           SL1      BDSU                                  
047804,000162: 13,2467           24005                                    DP1/2                                 #  COS**2(L)
047805,000163: 13,2470           44275                           DMPR     BDSU                                  
047806,000164: 13,2471           26505                                    EE                                    
047807,000165: 13,2472           24005                                    DP1/2                                 
047808,000166: 13,2473           75465                           BDDV     SQRT                                  
047809,000167: 13,2474           26501                                    B2XSC                                 
047810,000168: 13,2475           77622                           SR4R                                           
047811,000169: 13,2476           03673                           STORE    ERADM                                 
047812,000170: 13,2477           77616                           RVQ                                            
047813,000171: 
047814,000172:                                                                                                  #  THE FOLLOWING CONSTANTS WERE COMPUTED WITH A=6378166,B=6356784 METERS
047815,000173:                                                                                                  #  B2XSC= B**2 SCALED B-51
047816,000174:                                                                                                  #  B2/A2= B**2/A**2 SCALED B-1
047817,000175:                                                                                                  #  EE=(1-B**2/A**2) SCALED B-0
047818,000176: 13,2500           00446 00305  B2XSC              2DEC     .0179450689                            #  B**2 SCALED B-51
047819,000177: 
047820,000178: 13,2502  12,2004               DP1/2              =        XUNIT                                 
047821,000179: 13,2502           17711 05254  B2/A2              2DEC     .9933064884 B-1                        #  GAMMA= B**2/A**2 B-1
047822,000180: 
047823,000181: 13,2504           00155 25250  EE                 2DEC     6.6935116  E-3                        #  (1-B**2/A**2) B-0
047824,000182: 

Page 1128

047826,000184:                                                                                                  #  ARCTAN SUBROUTINE
047827,000185: 
047828,000186: 
047829,000187:                                                                                                  #  CALLING SEQUENCE
047830,000188: 
047831,000189:                                                                                                  #    SIN THETA IN SINTH B-1
047832,000190:                                                                                                  #    COS THETA IN COSTH B-1
047833,000191:                                                                                                  #    CALL ARCTAN
047834,000192: 
047835,000193:                                                                                                  #  OUTPUT
047836,000194:                                                                                                  #     ARCTAN THETA IN MPAC AND THETA B-0 IN RANGE -1/2 TO +1/2
047837,000195: 
047838,000196: 
047839,000197: 13,2506           77600        ARCTAN             BOV                                            
047840,000198: 13,2507           26510                                    CLROVFLW                              
047841,000199: 13,2510           63545        CLROVFLW           DLOAD    DSQ                                   
047842,000200: 13,2511           00023                                    SINTH                                 
047843,000201: 13,2512           63525                           PDDL     DSQ                                   
047844,000202: 13,2513           00021                                    COSTH                                 
047845,000203: 13,2514           77615                           DAD                                            
047846,000204: 13,2515           75454                           BZE      SQRT                                  
047847,000205: 13,2516           26534                                    ARCTANXX                              #  ATAN=0/0  SET THETA=0
047848,000206: 13,2517           40065                           BDDV     BOV                                   
047849,000207: 13,2520           00023                                    SINTH                                 
047850,000208: 13,2521           26541                                    ATAN=90                               
047851,000209: 13,2522           67542                           SR1      ASIN                                  
047852,000210: 13,2523           00025                           STORE    THETA                                 
047853,000211: 13,2524           50125                           PDDL     BMN                                   
047854,000212: 13,2525           00021                                    COSTH                                 
047855,000213: 13,2526           26530                                    NEGCOS                                
047856,000214: 13,2527           43545                           DLOAD    RVQ                                   
047857,000215: 13,2530           57545        NEGCOS             DLOAD    DCOMP                                 
047858,000216: 13,2531           43244                           BPL      DAD                                   
047859,000217: 13,2532           26536                                    NEGOUT                                
047860,000218: 13,2533           24005                                    DP1/2                                 
047861,000219: 13,2534           00025        ARCTANXX           STORE    THETA                                 
047862,000220: 13,2535           77616                           RVQ                                            
047863,000221: 
047864,000222: 13,2536           52025        NEGOUT             DSU      GOTO                                  
047865,000223: 13,2537           24005                                    DP1/2                                 
047866,000224: 13,2540           26534                                    ARCTANXX                              
047867,000225: 13,2541           75345        ATAN=90            DLOAD    SIGN                                  
047868,000226: 13,2542           11011                                    LODP1/4                               
047869,000227: 13,2543           00023                                    SINTH                                 
047870,000228: 13,2544           00025                           STORE    THETA                                 
047871,000229: 13,2545           77616                           RVQ                                            
047872,000230: 
047873,000231: 13,2546  12,2006               2DZERO             =        DPZERO                                
047874,000232: 

Page 1129

047876,000234:                                                                                                  #  ..... SETGAMMA SUBROUTINE .....
047877,000235:                                                                                                  #  SUBROUTINE TO SET GAMMA FOR THE LAT-LONG AND LALOTORV SUBROUTINES
047878,000236: 
047879,000237:                                                                                                  #   GAMMA = B**2/A**2 FOR EARTH (B-1)
047880,000238:                                                                                                  #   GAMMA = 1 FOR MOON (B-1)
047881,000239: 
047882,000240:                                                                                                  #  CALLING SEQUENCE
047883,000241:                                                                                                  #   L       CALL
047884,000242:                                                                                                  #   L+1            SETGAMMA
047885,000243: 
047886,000244:                                                                                                  #  INPUT
047887,000245:                                                                                                  #   LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047888,000246: 
047889,000247:                                                                                                  #  OUTPUT
047890,000248:                                                                                                  #   GAMMA IN GAMRP  (B-1)
047891,000249: 
047892,000250: 13,2546           43145        SETGAMMA           DLOAD    BOFF                                  #  BRANCH FOR EARTH
047893,000251: 13,2547           26503                                    B2/A2                                 #  EARTH GAMMA
047894,000252: 13,2550           01743                                    LUNAFLAG                              
047895,000253: 13,2551           26554                                    SETGMEX                               
047896,000254: 13,2552           77735                           SLOAD                                          
047897,000255: 13,2553           24005                                    1B1                                   #  MOON GAMMA
047898,000256: 13,2554           00011        SETGMEX            STORE    GAMRP                                 
047899,000257: 13,2555           77616                           RVQ                                            
047900,000258: 13,2556                        GAMRP              =        8D                                    
047901,000259: 

Page 1130

047903,000261:                                                                                                  #  .....SETRE SUBROUTINE .....
047904,000262:                                                                                                  #  SUBROUTINE TO SET RE (EARTH OR MOON RADIUS)
047905,000263: 
047906,000264:                                                                                                  #  RE= RM FOR MOON
047907,000265:                                                                                                  #   RE= RREF FOR FIXED EARTH RADIUS OR COMPUTED RF FOR FISCHER ELLIPSOID
047908,000266: 
047909,000267:                                                                                                  #  CALLING SEQUENCE
047910,000268:                                                                                                  #   L       CALL
047911,000269:                                                                                                  #   L+1            SETRE
047912,000270: 
047913,000271:                                                                                                  #  SUBROUTINES USED
047914,000272:                                                                                                  #   GETERAD
047915,000273: 
047916,000274:                                                                                                  #  INPUT
047917,000275:                                                                                                  #   ERADFLAG=0 FOR FIXED RE, 1 FOR COMPUTED RE
047918,000276:                                                                                                  #   ALPHAV +4= 1/2 SINL IF GETERAD IS CALLED
047919,000277:                                                                                                  #   LUNAFLAG=0 FOR EARTH,=1 FOR MOON
047920,000278: 
047921,000279:                                                                                                  #  OUTPUT
047922,000280:                                                                                                  #   ERADM= 504RM FOR MOON (METERS B-29)
047923,000281:                                                                                                  #   ERADM= ERAD OR COMPUTED RF FOR EARTH (METERS B-29)
047924,000282: 
047925,000283: 13,2556           71220        SETRE              STQ      DLOAD                                 
047926,000284: 13,2557           00051                                    SETREX                                
047927,000285: 13,2560           10003                                    504RM                                 
047928,000286: 13,2561           71214                           BON      DLOAD                                 #  BRANCH FOR MOON
047929,000287: 13,2562           01703                                    LUNAFLAG                              
047930,000288: 13,2563           26573                                    TSTRLSRM                              
047931,000289: 13,2564           10001                                    ERAD                                  
047932,000290: 13,2565           45014                           BOFF     CALL                                  #  ERADFLAG=0 FOR FIXED RE,1 FOR COMPUTED
047933,000291: 13,2566           00742                                    ERADFLAG                              
047934,000292: 13,2567           26571                                    SETRXX                                
047935,000293: 13,2570           26464                                    GETERAD                               
047936,000294: 13,2571           37673        SETRXX             STCALL   ERADM                                 #  EXIT WITH RE OR RM METERS B-29
047937,000295: 13,2572           00051                                    SETREX                                
047938,000296: 13,2573           77214        TSTRLSRM           BON      VLOAD                                 #  ERADFLAG=0,SET R0=RLS
047939,000297: 13,2574           00702                                    ERADFLAG                              #          =1     R0=RM
047940,000298: 13,2575           26571                                    SETRXX                                
047941,000299: 13,2576           02021                                    RLS                                   
047942,000300: 13,2577           64446                           ABVAL    SR2R                                  #  SCALE FROM B-27 TO B-29
047943,000301: 13,2600           77650                           GOTO                                           
047944,000302: 13,2601           26571                                    SETRXX                                
047945,000303: 13,2602  0000051               SETREX             =        S2                                    

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