| DATA_SET_DESCRIPTION |
Overview:
=========
This data set contains the Galileo spacecraft trajectory data in three
coordinate systems commonly used in the analysis of jovian magnetospheric
data. These include System III (1965.0), Jupiter Solar Equatorial (JSE),
and Jupiter Solar Magnetospheric (JSM) coordinates. The data are sampled
every minute inside of 30 Jupiter radii, every ten minutes between 30 and
100 Rj, and every 30 minutes outside of 100 Rj. The data are derived
from SPICE SP kernels which are archived at the NAIF Node of the PDS.
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Table 2. Galileo Orbit Information
-------------------------------------------------------------------
Orbit <--- Periapsis Info ----> <-- Apoapsis Info -->
Start Periapsis Range Local Apoapsis Range Local
Orb Date Date/Time Time Date Time
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J00 95-12-03 95-12-07 21:54 4.00 16:21 96-03-29 267.7 03:39
G01 96-06-23 96-06-28 00:31 11.03 15:36 96-08-09 125.3 03:24
G02 96-09-01 96-09-07 13:38 10.65 15:22 96-10-07 113.0 03:12
C03 96-11-02 96-11-06 13:31 9.21 15:34 96-11-27 89.1 03:28
E04 96-12-15 96-12-19 03:22 9.16 15:21 97-01-04 72.1 03:00
J05* 97-01-15 97-01-20 00:26 9.05 14:54 97-02-04 72.1 02:48
E06 97-02-16 97-02-20 20:55 9.12 14:28 97-03-14 89.2 02:20
G07 97-03-30 97-04-04 11:03 9.12 14:14 97-04-21 75.9 01:56
G08 97-05-04 97-05-08 11:42 9.27 13:29 97-06-02 100.2 01:21
C09 97-06-22 97-06-27 11:52 10.77 12:35 97-08-08 143.0 00:21
C10 97-09-14 97-09-18 23:10 9.17 12:44 97-10-13 98.9 00:36
E11 97-11-02 97-11-06 23:02 9.03 12:36 97-11-26 84.1 00:29
E12 97-12-15 97-12-16 06:35 8.80 12:29 97-12-20 46.6 00:37
J13* 98-02-09 98-02-10 23:09 8.85 12:33 98-03-06 95.2 00:25
E14 98-03-28 98-03-29 07:59 8.83 12:17 98-04-30 199.7 00:16
E15 98-05-30 98-06-01 02:34 8.85 12:12 98-06-26 100.4 00:03
E16 98-07-20 98-07-20 17:18 9.93 11:54 98-08-23 124.4 23:51
E17 98-09-25 98-09-26 08:26 8.91 11:44 98-10-24 110.4 23:34
E18 98-11-21 98-11-22 03:57 9.23 11:24 98-12-27 129.0 23:17
E19 99-01-31 99-02-01 02:38 9.24 10:56 99-03-18 154.3 22:40
C20 99-05-02 99-05-03 17:00 9.37 10:24 99-06-02 114.5 21:46
C21 99-06-29 99-07-02 05:04 7.27 10:04 99-07-22 89.0 21:57
C22 99-08-11 99-08-12 10:58 7.32 09:50 99-08-29 77.1 21:23
C23 99-09-13 99-09-14 19:57 6.55 09:17 99-09-27 65.7 20:46
I24 99-10-10 99-10-11 03:31 5.68 08:41 99-11-01 97.7 20:47
I25 99-11-25 99-11-26 23:30 5.94 08:39 99-12-15 87.2 20:28
E26 00-01-01 00-01-04 03:33 5.78 08:14 00-01-28 102.7 20:05
I27 00-02-20 00-02-22 12:30 5.85 07:56 00-04-06 154.4 19:55
G28 00-05-17 00-05-21 04:52 6.68 07:18 00-09-08 289.9 18:37
G29 00-12-27 00-12-29 03:26 7.49 06:03 01-03-11 216.3 17:37
C30 01-05-07 01-05-23 17:33 7.28 05:11 01-06-29 136.8 16:27
I31 01-08-04 01-08-06 04:52 5.93 04:14 01-09-10 132.2 16:05
I32 01-10-14 01-10-15 23:56 5.78 03:53 01-12-01 160.7 15:39
I33 02-01-16 02-01-17 16:23 5.54 03:13 02-06-13 348.1 14:21
A34 02-11-04 02-11-05 07:24 1.99 01:40 03-04-14 336.7 12:49
J35 03-09-21 03-09-21 18:57 Entry Time
* Solar conjunction - no data from this orbit
** Rj = 71492 km
Coordinates:
============
The Jupiter System III (1965) coordinate system follows the definition of
Dr. Alex Dessler in Appendix B of 'Physics of the Jovian Magnetosphere'
[DESSLER1983]. This coordinate system is the accepted standard for
analysis of data from the jovian system. System III is a spherical,
planetographic coordinate system where the planetary rotation rate of
(9h, 55m, 29.71s) is based on the rate of rotation of Jupiter's magnetic
field. The prime meridian is defined as the sub-Earth meridian at
00:00:00 UT on Jan 1, 1965. Range is measured from the Jupiter center of
mass. Longitude for standard System III is measured west. This direction
choice causes the coordinate system to be left-handed and to a stationary
or distant observer, longitude increases with time. Left handed
coordinate systems are not in common use among physicists. Both east
and west longitudes are included in this data set. Also included is the
local time of the spacecraft where noon is defined to be the sub-Sun
direction, midnight in the anti-Sun direction, etc.
The Jupiter Solar Equatorial (JSE) coordinate system is a Cartesian
coordinate system defined by using the Sun direction and the Jupiter
spin axis. Distances are measured from the Jupiter center of
mass and are provided here in units of jovian radii (1 Rj = 71492 km).
Z-axis is taken along the Jupiter spin axis, positive in the northern
hemisphere (OMEGA). The X-Z plane contains the instantaneous vector to
the Sun center of mass (SUN), as observed by Jupiter. Thus:
JSE_Z = OMEGA
JSE_Y = OMEGA x SUN
JSE_X = JSE_Y x JSE_Z
This coordinate system is primarily used in orbit analysis, analysis of
solar wind and interplanetary magnetic field data, and other data where
the solar wind flow direction (-X) is the dominant process.
The Jupiter Solar Magnetospheric (JSM) coordinate system is a Cartesian
coordinate system defined by using the Sun direction and the Jupiter
dipole moment vector as principal vectors. The dipole selected is the
best fit, centered dipole, defined to be tilted 9.6 degrees towards
202 degrees System III (1965.0) west longitude [CONNERNEY1981] in the
northern hemisphere. The positive X direction is taken to be the
instantaneous direction to the Sun center of mass, as observed by the
Jupiter center of mass. The XZ-plane is defined to contain the magnetic
dipole vector (M). Thus M x X = Y and X x Y = Z. Distances are measured
from the Jupiter center of mass and are provided here in units of jovian
radii.
The JSM coordinate system is primarily used in the analysis of data from
regions where both the solar wind flow velocity (-X) and the rotating Jovian
magnetic field are important but where the solar wind flow is still
the dominant force (near the magnetopause and in the magnetosheath).
Data Sampling:
==============
The data are sampled every minute inside of 30 Jupiter radii, every
ten minutes between 30 and 100 Rj, and every 30 minutes outside of 100 Rj.
Samples are taken on the even 1, 10 and 30 minute sample times.
Data Processing:
================
The trajectory data were created using code written by Steven Joy to
extract information from the SPICE (GO-J-SPICE-6-SPK-V1.0) products
produced by the Galileo project. The software used to create this
ephemeris is well tested and in agreement with similar software provided
by the Galileo project. All of the SPICE kernels used to produce this
data set are contained on the Io/J0 MWG archive volume CDROM in the
GEOMETRY directory.
Data:
=====
These data are derived from SPICE kernels produced by the Galileo NAV
team during the mission. All of the SPICE kernels used to produce this
data set are contained on the MWG archive volume DVD in the
EXTRAS/SPICE/KERNELS directory.
The kernels (PDS PRODUCT_ID) used to create this were:
S980326B.TSP - Prime Mission Reconstruction (JA - E12)
S000131A.TSP - GEM reconstruction (E12-E26)
S030129A.TSP - GMM (I27-A34) reconstruction, J35 predict
PCK00007.TPC - Planetary constants kernel (2000-04-24)
MK00062B.TSC - Galileo spacecraft clock kernel
All data are archived in ASCII tables (1 orbit/file) with the following
table structure:
Column Type Description
_________________________________________________________________________
time char Sample time in PDS time format number
R real Range from Jupiter in Rj where 1 Rj = 71492 km
S3_LAT real Jovigraphic latitude of the S/C
S3_WLON real System III west longitude of the S/C
JSE_X real X Jupiter Solar Equatorial (JSE) coordinates
JSE_Y real Y Jupiter Solar Equatorial (JSE) coordinates
JSE_Z real Z Jupiter Solar Equatorial (JSE) coordinates
JSM_X real X Jupiter Solar Magnetospheric (JSM) coordinates
JSM_Y real Y Jupiter Solar Magnetospheric (JSM) coordinates
JSM_Z real Z Jupiter Solar Magnetospheric (JSM) coordinates
local_hr real Local time (decimal hours)
mag_hr real Magnetic local time (decimal hours)
Local time definition:
Sun
^
|
noon Planetocentric
12:00 Equatorial Projection
|
|
|
| Jupiter
* * */
* | *
(dusk) 18:00 -----------*--|--*------------- 06:00 (dawn)
* |\ *
* * *
| \
| \
| \
|-HA--\
00:00
midnight
Local hour angle is the angle (HA) between the observer's (Galileo)
sub-Jupiter meridian and the anti-sunward meridian, measured in the
jovian equatorial plane in the direction of planetary rotation. Local
time is the conversion of the local hour angle into units of time by
using the conversion factor that equates one hour to fifteen degrees of
longitude. Magnetic local time follows the same convention with the
difference being that the reference pole is the dipole moment vector (M)
rather than the jovian spin axis (Omega). Local time values are provided
here in units of decimal hours.
Magnetic local time definition:
Sun
^
|
noon Dipole
12:00 Equatorial Projection
|
|
|
| Jupiter
* * */
* | *
(dusk) 18:00 -----------*--|--*------------- 06:00 (dawn)
* |\ *
* * *
| \
| \
| \
|-MHA-\
00:00
midnight
Magnetic local hour angle is the angle (MHA) between the observer's
dipole meridian and the anti-sunward meridian, measured in the
magnetic equatorial plane in the direction of planetary rotation.
Magnetic time is the conversion of the magnetic local hour angle into
units of time by using the conversion factor that equates one hour
to fifteen degrees of longitude. Magnetic local time values are provided
here in units of decimal hours.
Ancillary Data:
===============
SPICE kernels MK98264A.TLS (leapseconds), MK98264A.TLS (spacecraft
clock), PK96030A.TPC (planetary constants), S980326B.TSP, S991130A.TSP,
and S020128A.BSP (spacecraft/planetary ephemeris), and the rotor attitude
file ROT_ATT.TAB located in the GEOMETRY directory of the GOMW_5001 volume
can all be considered as ancillary data files for this data set. These are
the files that were used to generate this data set. Ideally, these data
should be generated on demand using the latest SPICE kernels available
from the NAIF Node of the PDS.
References:
===========
Russell, C.T., Geophysical coordinate transformations, Cosmic
Electrodynamics, Reidel Publishing Co., Vol. 2, 174-196, 1971.
Connerney, J. E. P., The magnetic field of Jupiter: A generalized
inverse approach, J. Geophys. Res., 86, 7679-7693, 1981.
Dessler, A. J., Appendix B Coordinate Systems, in Physics of the Jovian
Magnetosphere, (edited by A. J. Dessler), Cambridge Univ Press, 1983.
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