***** 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).