CCSD3ZF0000100000001NJPL3IF0PDSX00000001 PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "ULY-J-VHM/FGM-4-SUMM-JGCOORDS-60S-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "ULY JUP MAGNETIC FIELD JOVIGRAPHIC SYS III LH COORDS 60 AVGS" DATA_SET_COLLECTION_MEMBER_FLG = N START_TIME = 1992-02-05T00:00:30.000Z STOP_TIME = 1992-02-11T23:59:30.000Z DATA_SET_RELEASE_DATE = 1998-05-01 PRODUCER_FULL_NAME = "ROBERT J. FORSYTH" DETAILED_CATALOG_FLAG = N DATA_OBJECT_TYPE = "TIME SERIES" DATA_SET_DESC = " Data Set Overview ================= The data set covers the period Jan 25 through Feb 18, 1992 (days 25 to 48 inclusive). Files VHMxx_xx.TAB and FGMxx_xx.TAB contain one minute averages of the magnetic field components and magnitude measured by either the VHM (Vector Helium Magnetometer) or FGM (Fluxgate Magnetometer), where xx_xx = Days of Year covered (25 = Jan 25). The three days of closest approach (38-40) are FGM; the others are VHM. Data ==== Each line in the VHM/FGM files contains time in the format yyyy-mm-ddThh:mm:ss.sssZ (0000 hrs on Jan 25, 1992 would be 1992-01-25T00:00:00.000Z), BR, BTHETA, BPHI, BMAGNITUDE in the format (1x,a24, 4f10.3). The time tag is the midpoint of the one minute averaging interval. BMAGNITUDE is the average of the field magnitude, not the magnitude of the average field vector. Field units are nT. BR, BTHETA and BPHI are one-minute averages of the field components in R-THETA-PHI coordinates (see below). Processing ========== VHM files were produced by first averaging high resolution (1s or 2s) field data in inertial spacecraft coordinates. Then the averages were transformed into R-THETA-PHI coordinates, using parameters from the Final SEDR (Supplementary Experiment Data Records). FGM files were produced in a similar manner by R.J. Forsyth at Imperial College. All files were then reformatted at the PDS/PPI Node to provide time tags consistent with those used on the rest of the ULYSSES JUPITER ENCOUNTER CD-ROM (ULY_0001), and merged into multiple day files. Coordinate System ================= The field components are given in the R-THETA-PHI system, which is that conventionally used for comparison with models. The R axis is from Jupiter to Ulysses; the THETA axis is perpendicular to R and lies in the plane containing R and Jupiter's rotation axis and is positive southward; PHI completes the orthogonal right-handed system. The Ulysses at Jupiter EPHEM data includes all the parameters necessary to transform the field components into System III, ECL50, or inertial spacecraft coordinates. See Computation of Coordinate Transformations, below. The paragraphs below give methods for computing transformation matrices using trajectory parameters from the EPHEM files. As an alternative, note that the appendix in [SMITH&WENZEL1993] contains 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 [SMITH&WENZEL1993] 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 data 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 data. 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_NOTE = " Confidence Level Overview ========================= Since the VHM sensor has greater resolution (4 pT in the +/- 8 nT range), it was decided that the best quality dataset would consist of VHM data for the majority of the encounter period and FGM for days 38-40 when the VHM was in saturation. We feel that both VHM and FGM datasets have been individually calibrated to the best level that we can achieve at this time. It is possible that further small improvements could be made in the cross calibration between the two sensors; in the present dataset the differences between VHM and FGM at the beginning of day 38 and at the end of day 40 are less than 0.5 nT." 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