 +_____________________________________________________________________
  AUTHOR:                                          SMS: B28027      
  D. GASTEAZORO          BFS PROGRAM NOTE          DR:  109675      
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE: 7/02/96    
  RI/DNY 310-922-2146      RELEASE NOTE ( )                         
 ___________________________________________________________________
  OI/FLIGHT EFFECTIVITY:          USER AFFECTED:                     
  OI-25 THROUGH OI-26B            CREW ( )  GROUND (X)  DUMP ONLY ( )
 ____________________________________________________________________
            MAJOR SOFTWARE AREA:             OPS MODES AFFECTED:     
 BSL( ) BSS(X) GNC(X) SEQ( ) SM/SP( ) IPL( )  ALL                    
 _____________________________________________________________________
  SOFTWARE SUB-AREA: DOWNLIST                                         
 _____________________________________________________________________
  PRINCIPAL FUNCTIONS:                                                
  MG038106/3.2.5.2.4.2.3 GPS DOWNLIST REQUIREMENTS                    
  MG038101/TABLE 3.7.1.2.3-1(4) BFS DOWNLIST FORMATS 12 AND 13        
 _____________________________________________________________________
  TITLE: GPS DOWNLIST DATA NOT HOMOGENEOUS                            
 _____________________________________________________________________
  DESCRIPTION:                                                        
                                                                      
  POST-PROCESSING OF GPS DOWNLIST DATA COLLECTED FROM JAEL TEST       
  RUNS INDICATED THAT THE DOWNLISTED GPS PARAMETERS WERE NOT TIME     
  HOMOGENEOUS WITH THE GPS DATA SET IDENTIFIED IN MG038106, SECTION   
  3.2.5.2.4.2.3.                                                      
                                                                      
  ANY SET OF DATA THAT IS DOWNLISTED IN MULTIPLE FRAMES IS SUBJECT TO 
  BEING NON-HOMOGENEOUS IN ANY GIVEN DOWNLIST CYCLE.  THIS IS DUE TO  
  THE ASYNCHRONOUS NATURE OF THE BFS DOWNLIST AS PREVIOUSLY IDENTIFIED
  IN BFS USER NOTE B28711. THEREFORE THERE IS CONFLICT OF REQUIREMENTS
  BETWEEN THE MG038101 AND THE MG038106 REQUIREMENT DOCUMENTS.        
 _____________________________________________________________________
  USER RESPONSE:                                                      
                                                                      
  THE USER WILL SEE A NON-HOMOGENEOUS SET OF DATA CONSISTING OF       
  CURRENT GPS DATA COMBINED WITH PREVIOUS GPS DATA. THIS IS DUE TO    
  THE SET OF DATA THAT IS DOWNLISTED IN MULTIPLE FRAMES, WHICH WILL   
  BE NON-HOMOGENEOUS AT ANY GIVEN DOWNLIST CYCLE.                     
                                                                      
  AN ALGORITHM TO READ THE GPS DATA IN THE DOWNLIST IN A HOMOGENEOUS  
  FASHION IS DESCRIBED IN THIS OPS NOTES SUPPLEMENTAL SHEET.          
                          (CONTINUED)                                 
                                                                      
                                                                      
 _____________________________________________________________________
 CONCURRENCE:                           APPROVAL:                    
 RI: <S> D. CORBIN         DATE 10/08/96                             
     --------------------      ---------                             
 ASD:ERIC C. BINGHAM       DATE 10/10/96                             
     --------------------      --------- DARRELL E. STAMPER 10/15/96 
 PF MGR:DEBRA I. ELDRIDGE  DATE 10/10/96------------------- -------- 
        -----------------      --------- CHAIRMAN, SASCB      DATE   
 _____________________________________________________________________
 @


 +_____________________________________________________________________
                        SUPPLEMENTAL SHEET                            
                                                                      
 _____________________________________________________________________
  AUTHOR:                                          SMS: B28027      
  D. GASTEAZORO          BFS PROGRAM NOTE          DR:  109675      
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE: 7/02/96    
  RI/DNY 310-922-2146      RELEASE NOTE ( )                         
 ___________________________________________________________________
  TITLE: GPS DOWNLIST DATA NOT HOMOGENEOUS.                           
 _____________________________________________________________________
  USER RESPONSE: (CONT...)                                            
                                                                      
         "ALGORITHM TO OBTAIN DOWNLIST GPS HOMOGENEOUS DATA SETS"     
                                                                      
 GIVEN:                                                               
 V98Q0008C-GPC FRAME COUNT: THIS DATA IS IN FRAME 0 @ 25 HZ,          
           THIS VALUE IS DOWNLISTED EVERY MINOR CYCLE. VALUE IS       
           0-49.                                                      
 V98Q0565C-MINOR CYCLE COUNTER: THIS DATA IS IN FRAME 0 @ 1 HZ,       
           THIS VALUE IS DOWNLISTED EVERY SECOND. VALUE IS 0-23       
                                                                      
 BOS READS A NEW SET OF GPS DATA FROM THE GPS RECEIVER IN MINOR CYCLE 
 23.                                                                  
                                                                      
 ALGORITHM:                                                           
                                                                      
 1. WHEN READING THE GPC FRAME COUNT, THE VALUE READ SHOULD BE        
    CALCULATED AS MODULO 25. FOR EXAMPLE, IF THE VALUE IS 26, CONSIDER
    IT TO BE 1. (I.E. 26-25=1 )                                       
                                                                      
 2. SYNCH THE GPC FRAME COUNT WITH THE MINOR CYCLE COUNTER:           
    USING A DOUBLE BUFFERING SCHEME, IN WHICH EACH BUFFER CONTAINS 25 
    DOWNLIST FRAMES (I.E. ONE CURRENT DOWNLIST CYCLE AND ONE PREVIOUS 
    DOWNLIST CYCLE), KEEP READING THE DOWNLIST, ONE FRAME AT A TIME   
    UNTIL IT CAN BE DETERMINED THAT THE CURRENT DOWNLIST CYCLE BEGINS 
    AT GPC FRAME COUNT = 0, AND MINOR CYCLE COUNTER = 0. BE SURE TO   
    CYCLE THROUGH AT LEAST ONE COMPLETE TIME TO ALLOW FOR A COMPLETE  
    PREVIOUS DOWNLIST CYCLE.                                          
                                                                      
 3. AFTER THE TWO VARIABLES ARE IN SYNCH, THE FOLLOWING 2 TABLES      
    DEFINE THE FRAME NUMBER WHERE THE GPS ELEMENTS EXIST TO COMPOSE   
    THE HOMOGENEOUS GPS DATA SET, WHEN FRAME COUNT = 0 AND MINOR CYCLE
    COUNTER = X (0-23).                                               
                                                                      
                                                                      
 NOTE:                                                                
                                                                      
 IN THE FOLLOWING TABLES THERE WILL BE SOME MINOR CYCLES WHERE THE    
 DATA DOES NOT GET INTO THE DOWNLIST AND THEREFORE FOR THAT PARTICULAR
 MINOR CYCLE, IT IS NOT POSSIBLE FOR THE DATA TO BE HOMOGENEOUS,      
 (INDICATED BY N/A). THIS IS DUE TO THE FACT THAT THE DOWNLIST        
 PROCESSOR RUNS AT A FASTER RATE (1.04HZ) THAN THE DOWNLIST (1.00HZ). 
                                                                      
 P - INDICATES USE THE VALUE FROM THE PREVIOUS DOWNLIST CYCLE.        
 _____________________________________________________________________



 +_____________________________________________________________________
                        SUPPLEMENTAL SHEET                            
                                                                      
 _____________________________________________________________________
  AUTHOR:                                          SMS: B28027      
  D. GASTEAZORO          BFS PROGRAM NOTE          DR:  109675      
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE: 7/02/96    
  RI/DNY 310-922-2146      RELEASE NOTE ( )                         
 ___________________________________________________________________
  TITLE: GPS DOWNLIST DATA NOT HOMOGENEOUS.                           
 _____________________________________________________________________
                                                                      
  ASCENT MODE TABLE:                                                  
                       FRAME COUNT =0 AND MINOR CYCLE CNTR =X (0-23)  
 _____________________________________________________________________
                      0  1-5  6  7-9  10  11-20  21  22  23 
 ___________________________________________________________
 MSID     HAL NAME   N/A     N/A     N/A        N/A     N/A 
 ___________________________________________________________
 V98W7200CT_GPS_WEEK_   12      12       P12        P12     
          RCVR                                              
 ___________________________________________________________
 V98W7201CT_GPS_SEC_    16      P16      P16        P16     
          RCVR                                              
 ___________________________________________________________
 V98H7202CR_GPS_ECEF_   P24     P24      P24        P24     
          RCVR(1)                                           
 ___________________________________________________________
 V98H7203CR_GPS_ECEF_   1       1        1          P1      
          RCVR(2)                                           
 ___________________________________________________________
 V98H7204CR_GPS_ECEF_   1       1        1          P1      
          RCVR(3)                                           
 ___________________________________________________________
 V98L7205CV_GPS_ECEF_   1       1        1          P1      
          RCVR(1)                                           
 ___________________________________________________________
 V98L7206CV_GPS_ECEF_   P22     P22      P22        P22     
          RCVR(2)                                           
 ___________________________________________________________
 V98L7207CV_GPS_ECEF_   P22     P22      P22        P22     
          RCVR(3)                                           
 ___________________________________________________________
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________


 +_____________________________________________________________________
                        SUPPLEMENTAL SHEET                            
                                                                      
 _____________________________________________________________________
  AUTHOR:                                          SMS: B28027      
  D. GASTEAZORO          BFS PROGRAM NOTE          DR:  109675      
 ____________________                             __________________
  ORG/PHONE:          OPS NOTE (X)  USER NOTE ( )  DATE: 7/02/96    
  RI/DNY 310-922-2146      RELEASE NOTE ( )                         
 ___________________________________________________________________
  TITLE: GPS DOWNLIST DATA NOT HOMOGENEOUS.                           
 _____________________________________________________________________
                                                                      
  DESCENT MODE TABLE:                                                 
                       FRAME COUNT =0 AND MINOR CYCLE CNTR =X (0-23)  
 _____________________________________________________________________
                     0-2 3 4-5 6-7 8-17 18 19-20 21  22 23 
 __________________________________________ _______________
 MSID     HAL NAME      N/A   N/A      N/A      N/A     N/A
 ____________________________________________ _____________
 V98W7200CT_GPS_WEEK_4     4       4       P4       P4     
          RCVR                                             
 __________________________________________________________
 V98W7201CT_GPS_SEC_ 15    15      P15     P15      P15    
          RCVR                                             
 __________________________________________________________
 V98H7202CR_GPS_ECEF_P24   P24     P24     P24      P24    
          RCVR(1)                                          
 __________________________________________________________
 V98H7203CR_GPS_ECEF_1     1       1       1        P1     
          RCVR(2)                                          
 __________________________________________________________
 V98H7204CR_GPS_ECEF_1     1       1       1        P1     
          RCVR(3)                                          
 __________________________________________________________
 V98L7205CV_GPS_ECEF_1     1       1       1        P1     
          RCVR(1)                                          
 __________________________________________________________
 V98L7206CV_GPS_ECEF_19    P19     P19     P19      P19    
          RCVR(2)                                          
 __________________________________________________________
 V98L7207CV_GPS_ECEF_16    16      P16     P16      P16    
          RCVR(3)                                          
 __________________________________________________________
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________
 @
