***** File TRAJ_ICE.DOC                                                       
                                                                              
                                                                              
            ICE Trajectory for Giacobini-Zinner Encounter                     
            ---------------------------------------------                     
                                                                              
        The ICE trajectory information is from the "SAVE TAPE"  produced by   
 the JPL Navigation Section after the Giacobini-Zinner (G-Z) encounter. The   
 data and documentation were provided by J. Wolf (JPL) who also provided the  
 comet encounter magnetic field data from the magnetometer experiment on      
 the ICE spacecraft. The spacecraft position and velocity components are      
 given in geocentric and heliocentric coordinates for Earth true-equator-of-  
 date and Earth true-orbit-of-date systems and body-fixed coordinates         
 relative to Earth, G-Z, and Venus. Various angles relative to these          
 and other bodies are also given.                                             
                                                                              
        The trajectory data cover the period September 10-14, 1985, and       
 are in one ASCII file containing hourly values for each of 114 parameters.   
 The deviation of the spacecraft from uniform linear motion was negligible    
 during the G-Z encounter, making interpolation of the trajectory             
 straightforward. The data are in the form of a continuous byte-stream        
 and should be grouped into 2736-byte logical records for proper              
 decoding.                                                                    
                                                                              
        Records contain 114 data items in the format                          
 (2D24.16, 2I12, 111D24.16).  Note that the third data item (VIGDAT) is       
 actually two integer words. Example:                                         
                                                                              
              __1985090010___110000000 =   1985-Sept-10, 11:00:00 UT          
                                                                              
 Thus, the data record size = 114 data items * 24 bytes/item = 2736 bytes.    
 The data records do not contain any trailing blanks, and there are no        
 trailing blanks at the end of the file.                                      
                                                                              
        There is one record per hour. Body 1 is Giacobini-Zinner; Body 2 is   
 Venus. The parameter FERP has the value 22.0, so parameters 35-62 use        
 the ecliptic of date as the reference plane. Parameters 68 and 69, in the    
 coordinate system fixed in Body 1, do not contain meaningful data.           
                                                                              
        Position and velocity of ICE relative to G-Z can be found in          
 items 47-49, 50-52, 59, 60 & 70.                                             
                                                                              
        There are 24 records/day and 5 days of data, making 120 data          
 records, plus 1 header record, resulting in a file size of 121*2736          
 = 331056 bytes.                                                              
                                                                              
                                                                              
                                                                              
                                                                              
 Item                                                Character Header         
 Number     Description                                  Record Name          
                                                                              
   1       Double precision time in seconds               ETSP50              
           (ET) past 0h, Jan 1, 1950                                          
   2       DP Julian Date, Days                           JULDAT              
   3       Gregorian Calendar Date (2 integer             VIGDAT              
           words which represent the vigesimal                                
           date); see example above                                           
   4       Time from launch, sec                          TFLANC              
   5       Time from injection, sec                       TFINJE              
   6       ET - UTC, sec                                  ETMUTC              
   7       DPTRAJ Alarm word corresponding                DALARM              
           to this epoch                                                      
                                                                              
Geocentric (Spacefixed Earth true equator of date system)                     
                                                                              
   8       Range rate of probe, km/sec                    RANGRP              
   9       Magnitude of velocity vector, km/sec           MAGVEL              
  10       Inertial path angle, deg                       INPATH              
  11       Inertial azimuth angle, deg                    INAZIM              
  12       Earth-probe range, km                          REARPR              
  13       Declination of probe, deg                      DECPRO              
  14       Right ascension of probe, deg                  RTASCP              
  15       Earth-Sun range, km                            REARSU              
  16       Declination of Sun, deg                        DECSUN              
  17       Right ascension of Sun, deg                    RTASCS              
  18       Earth-Moon range, km                           REARMO              
  19       Declination of Moon, deg                       DECMOO              
  20       Right ascension of Moon, deg                   RTASCM              
                                                                              
 Heliocentric (Spacefixed Earth true orbital of date system)                  
                                                                              
  21       Range to probe, km                             HRANGP              
  22       Probe inertial velocity, km/sec                HMAGVP              
  23       Probe inertial path angle, deg                 HINPTH              
  24       Celestial latitude of probe, deg               CELLTP              
  25       Celestial longitude of probe, deg              CELLNP              
  26       Celestial latitude of Earth, deg               CELLTE              
  27       Celestial longitude of Earth, deg              CELLNE              
  28       X component of S/C in Sun-Earth---+                                
           line, km                          |            XSCSEL              
  29       Y component of S/C in Sun-Earth   |                                
           line, km                           > Ecliptic  YSCSEL              
  30       Z component of S/C in Sun-Earth   |  Plane                         
           line, km                          |  of        ZSCSEL              
  31       Sun-probe distance in Sun-Earth   |  Date                          
           X-Y plane, km               ------+            SPSEXY              
  32       Longitude of S/C in Sun-Earth                                      
           line system, deg                               LNPSEL              
  33       Integrating central body number                ICBODY              
  34       Flag for equinox and reference                                     
           plane for items 35 through 62                  FERPFL              
                                                                              
                          NOTES                                               
                                                                              
               FERP = 11. means Earth mean equator of 1950.0                  
               FERP = 12. means Earth mean orbit of 1950.0                    
               FERP = 21. means Earth true equator of date                    
               FERP = 22. means Earth true orbit of date                      
                                                                              
 Space-fixed FERP Coordinate System                                           
                                     _                                        
  35       X component of geocentric r of S/C, km            XPGSFF           
  36       Y component of geocentric r of S/C, km            YPGSFF           
  37       Z component of geocentric r of S/C, km            ZPGSFF           
  38       X component of geocentric dr/dt of S/C, km/sec    DXPGSF           
  39       Y component of geocentric dr/dt of S/C, km/sec    DYPGSF           
  40       Z component of geocentric dr/dt of S/C, km/sec    DZPGSF           
  41       X component of heliocentric r of S/C, km          XPHSFF           
  42       Y component of heliocentric r of S/C, km          YPHSFF           
  43       Z component of heliocentric r of S/C, km          ZPHSFF           
  44       X component of heliocentric dr/dt of S/C, km/sec  DXPHSF           
  45       Y component of heliocentric dr/dt of S/C, km/sec  DYPHSF           
  46       Z component of heliocentric dr/dt of S/C, km/sec  DZPHSF           
  47       X component of body 1 - S/C r, km                 XP1SFF           
  48       Y component of body 1 - S/C r, km                 YP1SFF           
  49       Z component of body 1 - S/C r, km                 ZP1SFF           
  50       X component of body 1 - S/C dr/dt, km/sec         DXP1SF           
  51       Y component of body 1 - S/C dr/dt, km/sec         DYP1SF           
  52       Z component of body 1 - S/C dr/dt, km/sec         DZP1SF           
  53       X component of body 2 - S/C r, km                 XP2SFF           
  54       Y component of body 2 - S/C r, km                 YP2SFF           
  55       Z component of body 2 - S/C r, km                 ZP2SFF           
  56       X component of body 2 - S/C dr/dt, km/sec         DXP2SF           
  57       Y component of body 2 - S/C dr/dt, km/sec         DYP2SF           
  58       Z component of body 2 - S/C dr/dt, km/sec         DZP2SF           
  59       Body 1 - S/C range, km                            B1MAGR           
  60       Body 1 - S/C velocity, km/sec                     B1MAGV           
  61       Body 2 - S/C range, km                            B2MAGR           
  62       Body 2 - S/C velocity, km/sec                     B2MAGV           
                                                                              
 Body-Fixed Coordinate Systems                                                
                                                                              
 Earth                                                                        
                                                                              
  63       Latitude of probe, deg                         EALATP              
  64       Longitude of probe, deg                        EALONP              
  65       Velocity of probe relative to body, km/sec     EAVELP              
  66       Body fixed path angle of probe, deg            EAPTHP              
  67       Body fixed azimuth angle of probe, deg         EAAZIP              
                                                                              
 Body 1                                                                       
                                                                              
  68       Latitude of probe, deg                        B1LATP               
  69       Longitude of probe, deg                       B1LONP               
  70       Velocity of probe relative to body, km/sec    V1VELP               
  71       Body fixed path angle of probe, deg           B1PTHP               
  72       Body fixed azimuth angle of probe, deg        B1AZIP               
                                                                              
 Body 2                                                                       
                                                                              
  73       Latitude of probe, deg                       B2LATP                
  74       Longitude of probe, deg                      B2LONP                
  75       Velocity of probe relative to body, km/sec   B2VELP                
  76       Body fixed path angle of probe, deg          B2PTHP                
  77       Body fixed azimuth angle of probe, deg       B2AZIP                
                                                                              
                            NOTE                                              
                                                                              
              If body 1 or body 2 has no defined                              
              body-fixed coordinate system,                                   
              corresponding values will be zero.                              
                                                                              
 Angle Group  (all angles in deg)                                             
                                                                              
  78       Earth-probe-body 1 angle                     EPB1AN                
  79       Earth-probe-body 2 angle                     EPB2AN                
  80       Earth-probe-Sun angle                        EPSUAN                
  81       Earth-probe-moon angle                       EPMOAN                
  82       Canopus-probe-Earth angle                    CPEANG                
  83       Canopus-probe-Sun angle                      CPSANG                
  84       Moon-probe-Sun angle                         MOPSAN                
  85       Body 1-probe-body 2 angle                    B1PB2A                
  86       Moon-Earth-probe angle                       MOEPAN                
  87       Sun-Earth-probe angle                        SEPANG                
  88       Earth-Sun-probe angle                        ESPANG                
  89       Sun-probe-body 1 angle                       SPB1AN                
  90       Sun-probe-body 2 angle                       SPB2AN                
  91       Body 1-Earth-probe angle                     B1EPAN                
  92       Body 2-Earth-probe angle                     B2EPAN                
                                                                              
           Cone and Clock Set                                                 
                                                                              
 Sun-Probe-Canopus System, deg                                                
                                                                              
  93       Cone angle of Earth                          CONECE                
  94       Clock angle of Earth                         CLCKCE                
  95       Cone angle of Body 1                         CONEC1                
  96       Clock angle of Body 1                        CLCKC1                
  97       Cone angle of Body 2                         CONEC2                
  98       Clock angle of Body 2                        CLCKC2                
                                                                              
 Sun-Probe-Earth System                                                       
                                                                              
  99       Body 1 cone angle                            CONEE1                
 100       Body 1 clock angle                           CLCKE1                
 101       Body 2 cone angle                            CONEE2                
 102       Body 2 clock angle                           CLCKE2                
 103       Canopus cone angle                           CONEEC                
 104       Canopus cone angle                           CLCKEC                
                                                                              
 Sun-Probe-Body 1 System                                                      
                                                                              
 105       Earth cone angle                             CONE1E                
 106       Earth clock angle                            CLCK1E                
 107       Body 2 cone angle                            CONE12                
 108       Body 2 clock angle                           CLCK12                
 109       Canopus cone angle                           CONE1C                
 110       Canopus clock angle                          CLCK1C                
                                                                              
 Miscellaneous                                                                
                                                                              
 111       Physical central body number                PCBODY                 
 112       Body number of input body 1                 BODY01                 
           (SPBOD(1)                                                          
 113       a) Body number of input body 2              BODY02                 
              (SPBOD(2))                                                      
           b) Body number of satellite if                                     
              PERIAP = 3 or 4                                                 
 114       Flag for periapsis                          PERIAP                 
            PERIAP= 0. for closest approach                                   
                    1. for periapsis to PCB                                   
                    2. for apoapsis to PCB                                    
                    3. for periapsis to satellite in 113 b).                  
                    4. for apoapsis to satellite in 113 b).