Ulysses Trajectory Bundle
Ulysses Ephemeris Data Description
PDS3 DATA_SET_ID = ULY-J-EPHEM-6-SUMM-SYS3/ECL50-V1.0
ORIGINAL DATA_SET_NAME = ULY JUPITER ENCOUNTER EPHEMERIS
SYS3/ECL50 COORDS. VER. 1.0
START_TIME = 1992-01-25T02:59:59.000
STOP_TIME = 1992-02-17T23:00:00.000
PDS3 DATA_SET_RELEASE_DATE = 1998-05-01
PRODUCER_FULL_NAME = ROBERT J. FORSYTH
Collection Overview
=================
This collection contains Ulysses ephemeris data near Jupiter
covering the dates 1992-01-25 to 1992-02-18. Two slightly
different versions of these data are included. The first
(TRJ25_48.TAB), provided by the Ulysses MAG team (Imperial
College/JPL), includes position data in Sys 3 spherical, ECL50
spherical, and ECL50 Cartesian coordinates. The Ulysses spin
axis position is also provided in ECL50 spherical coordinates.
The second version (SPK25_48.TAB), generated at the PDS/PPI
node (UCLA), includes Sys 3 spherical trajectory, plus a
spacecraft local time. Note that the position values for these
two versions differ slightly. This variation is due to
differences in the definitions of the Jovian physical
constants used to generate them.
Data
====
TRJ25_48.TAB
------------
The file TRJ25_48.TAB contains positions and attitude of
Ulysses. Time resolution is the same as the final SEDR: 3
hours for Days 25-31, 1 minute for Days 32-47, 1 hour for Day
48.
This file simply contains convenient extractions of parameters
from the Final SEDR. These were reformatted at the PDS/PPI
node to provide time tags consistent with those used on the
rest of the ULYSSES JUPITER ENCOUNTER CD-ROM, and merged from
multiple data files into a single encounter file.
TRJ25_48.TAB is an ASCII (CR/LF) format file consisting of the
following columns:
column type description
time a24 time in the format yyyy-mm-ddThh:mm:ss.sssZ
R f10.5 distance from Jupiter to Ulysses (RJ; 1 RJ =
71398 km)
RLATJG f8.3 spacecraft jovian (Sys 3) latitude (degrees)
RLONJG f8.3 spacecraft west (Sys 3) longitude (degrees)
RLATEC f8.3 latitude of the Jupiter-to-Ulysses unit
vector in ECL50 (degrees)
RLONEC f8.3 longitude of the Jupiter-to-Ulysses unit
vector in ECL50 (degrees)
AXISLAT f8.3 latitude of Ulysses spin axis in ECL50
(degrees)
AXISLON f8.3 longitude of Ulysses spin axis in ECL50
coordinates (degrees)
XSU 1pe15.8 Cartesian X of Sun-to-Ulysses vector in
ECL50 (km)
YSU 1pe15.8 Cartesian Y of Sun-to-Ulysses vector in
ECL50 (km)
ZSU 1pe15.8 Cartesian Y of Sun-to-Ulysses vector in
ECL50 (km)
This file may be read according to the fortran format
statement: '(a24,1x,f10.5,6(1x,f8.3),3(1x,1pe15.8))'.
SPK25_48.TAB
------------
This file contains positions in Sys 3 coordinates,
plus a local time to provide a sun reference. Positions are
provided in 60 second samples for the entire interval. Times
coincide with those for the 60 second averaged magnetometer
data provided to the PDS/PPI node by the Ulysses MAG team.
These data were generated from Ulysses SPICE at the PDS/PPI
node (UCLA). SPICE uses the latest IAU conventions as the
Jovian physical constants. The values used in this case
were those cited in the 1991 IAU report. The value used for
1 RJ = 71492 km.
SPK25_48.TAB is an ASCII (CR/LF) format file consisting of the
following columns:
column type description
time a24 time in the format yyyy-mm-ddThh:mm:ss.sssZ
R f10.5 Jupiter to spacecraft range (jovian radii)
LAT f8.3 spacecraft Jovian (Sys 3) latitude
(degrees)
LON f8.3 spacecraft Jovian west longitude (degrees)
LocTime f8.3 angular separation between the meridian
containing the sun and the one containing
the spacecraft converted to a time. The sun
meridian is defined to be noon (12.000), with
midnight (0.000) opposite it. Dawn (6.000)
and dusk (18.000) are where the sun rises and
sets according to the planet's rotation
This file may be read according to the fortran format
statement: '(a24,1x,f10.5,3(1x,f8.3))'.
Coordinate System
=================
System III (1965.0) (Sys 3) is a jovicentric left handed
coordinate system defined such that longitude increases with
time as viewed by a stationary remote observer.
Jovicentric System III (1965.0) spherical coordinates
R Jupiter to spacecraft range (positive away from
Jupiter)
LAT completes the left handed, orthogonal set
LON System III (1965) west longitude (with longitude
increasing westward from a specific jovian prime
meridian)
Coordinate Transformation Matrices
----------------------------------
The file TRJ25_48.TAB contains all the parameters necessary to
transform the field components into System III, ECL50, or
inertial spacecraft coordinates. The paragraphs below give
methods for computing transformation matrices using these
parameters. As an alternative, the orbital elements of Ulysses
with respect to Jupiter and demonstrates how to calculate the
position of Ulysses in System III and other coordinate systems
without recourse to trajectory data files.
The transformation matrix from R-THETA-PHI to System III
(1965.0) consists of the column vectors of the R, THETA, and
PHI axes expressed in System III. The R-axis in System III is
cos(RLATJG) cos(360-RLONJG), cos(RLATJG) sin(360-RLONJG),
sin(RLATJG). The PHI axis is the normalized crossproduct J x
R, where J is the rotation axis which is just 0,0,1, so the
unit vector in the PHI direction is -sin(360-RLONJG),
cos(360-RLONJG), 0. The unit vector in the THETA direction is
the crossproduct PHI x R = sin(RLATJG) cos(360-RLONJG),
sin(RLATJG) sin(360-RLONJG), -cos(RLATJG).
The transformation matrix from R-THETA-PHI back to ECL50
consists of the column vectors of the R, THETA, and PHI axes
expressed in ECL50. R is cos(RLATEC) cos(RLONEC), cos(RLATEC)
sin(RLONEC), sin(RLATEC). PHI is the normalized crossproduct
J x R, where J (North Pole of Jupiter) is given in the
reference as -92.002 RA, 64.504 DEC, Earth Mean Equinox and
Equator 1950.0. Rotating by 23.4458 deg (1950.0 obliquity)
gives J in ECL50 = (-.015037545, -.035534090, 0.999255323).
The THETA axis is PHI x R.
Inertial spacecraft coordinates are defined as follows: Z is
the Ulysses spin axis, which points approximately towards
Earth; X is is perpendicular to Z and lies in the plane
containing Z and S, where S is the Ulysses-to-Sun vector. X is
positive toward the Sun. Z in ECL50 is cos(AXISLAT)
cos(AXISLON), cos(AXISLAT) sin(AXISLON), sin(AXISLAT). S in
ECL50 is -XSU, -YSU, -ZSU. The Y axis is the normalized
crossproduct Z x S, and the X axis is Y x Z. The
transformation matrix from ECL50 back to inertial spacecraft
coordinates consists of the column vectors X, Y, and Z.
The EPHEM files in this submission include all the parameters
necessary to calculate the above transformations. In a few
cases where the direction of the spin axis was not available
in the SEDR, the Ulysses-to-Earth direction was substituted in
the EPHEM files. It is suggested that interpolations in time
be performed on vector components rather than angles in order
to avoid difficulties near 0 or 360, and that double precision
arithmetic be used in matrix multiplication.
Confidence Level Overview
=========================
As noted above, the two versions of Sys 3 ephemeris provided
contain slightly different values. In the case of R, the
variation is due to two different definitions of the Jovian
radius. A value of 1 RJ = 71398 km was used to generate
TRJ25_48.TAB, and a value of 1 RJ = 71492 km was used for
SPK25_48.TAB. The reason why latitude and longitude values
differ is unknown (though possibly due to different
definitions of the position of Jupiter's magnetic pole, or
statistical variation).
The differences in the values contained in the two versions
are summarized below:
COLUMN MINIMUM MAXIMUM AVERAGE
NAME VALUE VALUE VALUE
RJG 6.3052 262.609 80.6974
RLATJG -37.512 39.854 -12.7527
RLONJG 0.001 359.999 180.357
R 6.29692 262.264 80.5913
LAT -37.5168 39.859 -12.754
LON 0.00591442 359.999 180.372
dR -0.345123 -0.0082798 -0.106104
dLAT -0.00553894 0.00556946 -0.00129919
dLON -0.0112224 359.998 0.0146073
where: RJG : Jupiter-to-s/c range (TRJ25_48.TAB)
RLATJG : s/c latitude (TRJ25_48.TAB)
RLONJG : s/c west longitude (TRJ25_48.TAB)
R : Jupiter-to-s/c range (SPK25_48.TAB)
LAT : s/c latitude (SPK25_48.TAB)
LON : s/c west longitude (SPK25_48.TAB)
dR = R - rjg
dLAT = LAT - rlatjg
dLON = LON - rlonjg
TRJ25_48.TAB
------------
For the position of Ulysses in Jupiter-centered coordinates,
1-sigma uncertainties are less than 1 part in 1 million, or
less than 0.5 km at closest approach.
The attitude of Ulysses during the Jupiter encounter interval
is stated to be accurate within +/- 0.005 degrees.
SPK25_48.TAB
------------
Spacecraft positions were derived from SPICE using software
that has been extensively tested. They should give as accurate
representation of spacecraft ephemeris as possible using these
kernels.
Comparisons between these data and data from previous Jupiter
missions should be performed with caution. Some key parameters
(such as the Jovian radius) have changed from mission to
mission. Definitions for Jupiter's spin rate and the
orientation of its spin-axis have also changed slightly since
the early Pioneer days.
These data were generated using the current definition of the
Jovian radius, 71492 km. The spin rate used in generating these
data is the same as that used for System III (1965), +870.536
degrees/24 hours.
References
==========
Balogh, A., T.J. Beek, R.J. Forsyth, P.C. Hedgecock, R.J.
Marquedant, E.J. Smith, D.J. Southwood, and B.T. Tsurutani,
The magnetic field investigation on the Ulysses mission:
Instrumentation and preliminary scientific results, Astron.
Astrophys. Suppl. Ser. 92, 221-236, 1992.
Balogh, A., M.K. Dougherty, R.J. Forsyth, D.J. Southwood, E.J.
Smith, B.T. Tsurutani, N. Murphy, and M.E. Burton, Magnetic
field observations during the Ulysses flyby of Jupiter,
Science, 257, 1515-1518, 1992.
(https://doi.org/10.1126/science.257.5076.1515)
Smith, E.J., and K.-P. Wenzel, Introduction to the Ulysses
Encounter with Jupiter, J. Geophys. Res., 98, 21111, 1993.
(https://doi.org/10.1029/93JA02584)
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