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)