Data Set Overview : This data set contains magnetic field vectors acquired by the Galileo magnetometer at the Io flyby on Dec 7 (341), 1995 and for the remainder of the mission after the Phase 2 flight Software load in May 1996. Packetized data replaced the Experimenter Data Records (EDRs) that were the raw data product in Phase 1. These are raw data provided in their original packet form. Processing done internal to the instrument remains in the data set.   Processing : The onboard data processing of the magnetometer is as follows:  - Analog anti-aliasing filter applied - A/D conversion to 30 vectors per second - 1/4 - 3/4 digital recursive filter is applied, current output is 1/4 of the current input plus 3/4 of the previous output, - Data are decimated to 3 vectors second (1,2), - Offsets are subtracted from the sensor data, - Gains are applied (multiplied) to the sensor data, - Geometry matrix is applied to transform data into spinning spacecraft coordinates, - Data are collected by CDS when recording LPW data, - Data are decimated to 1 vector every minor frame - Data are despun into IRC coordinates using the spin phase angle broadcast on the BUS - Data are recursively filtered, - CDS picks up data from MAG memory address 4800 at RTS data rate appropriate for telemetry format.  1) The Io encounter was recorded in Phase 1 at a rate of 4.5 vectors/second. 2) An error in the MAG flight software caused data to be unevenly sampled on RT1 0 and 5 for the G1 and G2 flybys. A one byte patch to the software was loaded during the G2 cruise. Data from C3 through the end of mission are sampled on RTI 0 and 4.   Data : The data are stored in a rather complex and compact binary form called a packet. The details of where all of the bits are located are contained in Galileo project documents (3-280, 3-640, 3-505). The data are provided in engineering units. The conversion to nanoTesla requires division by a scale factor which depends on the instrument gain state (range).  Scale Factor Range measurable field ------------------------------------------------------ 2 Inboard High +/- 16,383 nT 64 Inboard Low +/- 512 nT 64 Outboard High +/- 512 nT 1024 Outboard Low +/- 32 nT   Ancillary Data : In order to rotate the MAG data into geophysical coordinate systems, several angles from the Attitude and Articulation Control Subsystem (AACS) are needed. The raw AACS packets are included as ancillary data to magnetometer data.  The 'as run' sequence of events (SEF) files which integrate all spacecraft commands are included as ancillary data. The sequence contains all of the information regarding the configuration of the instrument and spacecraft that affects the contents of the data files. Commands of special interest are:   6TMSED (telemetry format, sets RTS rate for MAG when selected**) 6TMREC (record mode format change) 6RCSET,6RCCLR (record rate change coverage on, off respectively) 6RCSEL,6RCDSL (record select, deselect respectively) 6RTSL, 6RTDS (RTS select and deselect respectively) 35A, 35AR (MAG power on, off respectively) 35KA, 35KAR (MAG memory keep alive power on, off respectively) 35DML (Mag direct memory load) 35IS, 35ISR (MAG inboard sensor on, off respectively) 35US, 35USR (MAG outboard sensor on, off respectively) 35ISL, 35ISH (MAG inboard sensor range low, high respectively) 35USL, 35USH (MAG outboard sensor range low, high respectively) 35AV, 35AVR (MAG optimal averager on, off respectively) 35SS, 35SSR (MAG snapshot on, off respectively) 35F, 35FR (MAG flipper power on, off respectively) 35IFL, 35IFR (MAG inboard sensor flip left, right respectively) 35UFL, 35UFR (MAG outboard sensor flip left, right respectively) 35IC, 35ICR (MAG internal calibration coil on, off respectively) 40CP, 40CPR (MAG external calibration coil on, off respectively)   The 35DML command is generally directed to memory address 4E80 (HEX) where it is processed by the instrument on the next major frame boundary. The contents are surrounded by the flag value A5A5. The values between the flags are 2 bytes (HEX) each and are in the order scale, avg const, avg rate, gain 1-3, offset 1-3, matrix (1,1), (1,2),... (3,3). A typical 35DML command looks something like:  03483012:28:0 96-169/00:29:30.200 CMD,35DML,272MA4D,, 96-169/00:29:30.200,4E80,A5,A5,04,00,01,00,00,03, 3D,F2,3E,C0,3E,31,F4,39,09,5A,D0,D8,FF,FA,F8,F8, 7F,FE,7F,FC,FC,E8,FF,EB,00,74,7F,FD,04,DD,A5,A5; << DIRECT MEMORY LOAD >>;  where  scale : 0400 gains : 3DF2, 3EC0, 3E31 (sensor 1, 2, 3) offsets : F439, 095A, D0D8 (sensor 1, 2, 3) matrix : FFFA F8F8 7FFE 7FFC FCE8 FFEB 0074 7FFD 04DD  Any 35DML command to addresses less than 4800 are acted upon immediately. These commands are not 'protected' by the A5A5 flag pair. Gains, offsets, and the matrix are stored contiguously in memory beginning at address 4714. Offset updates are commonly implemented this way directly to address 471A. The MAG executor code resides in address between 4000 and 46FF. Commands to this address space are flight software patches or loads.  ** RTS data formats  Telemetry MAG minor frames corner format bps per sample freq (Hz) --------------------------------------------- A-D 2 36 1/34 E 4 18 1/34 F 6 12 1/17 G 8 9 1/17 H 12 6 1/17 I 16 4 1/17   Software : Software has been provided by the magnetometer team to read the PKT data and output binary or ASCII tables of the mag vectors and AACS angles. Source code and Sun Solaris executables are provided. This is not PDS provided software. PDS does not expressly nor implicitly guarantee or warranty user supplied software.   Coordinate System : The data are provided in spacecraft coordinates. The RTS data are despun into IRC coordinates. The recorded data are not despun. The IRC coordinate system is roughly X parallel to the southward ecliptic normal, Z anti-earthward, and Y completing the righthanded set. The spinning coordinate system spins about the Z axis as described by the spin phase angle.  References : [KIVELSONETAL1992] Kivelson, et al, The Galileo Magnetic Field Investigation, Space Science Rev. 60, 357 (1992) [KIVELSONETAL1996A] Kivelson et al, A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer, Science, 273, p337, 1996(A) [KIVELSONETAL1996B] Kivelson et al, Io's Interaction with the Plasma Torus, Science, 274, p396, 1996(B) [KIVELSONETAL1996C] Kivelson et al, Discovery of Ganymede's magnetic field by the Galileo spacecraft, Nature, 384, p537, 1996(C) [KIVELSONETAL1997A] Kivelson et al, Galileo at Jupiter: Changing States of the Magnetosphere and First Looks at Io and Ganymede, Adv in Space Res., v20, No. 2, p193, 1997(A) [KIVELSONETAL1997B] Kivelson et al, Europa's magnetic signature: Report from Galileo's first pass on December 19, 1996, Science, 276, p1239, 1997(B) [KIVELSONETAL1997C] Kivelson et al, Intermittent Short-Duration Plasma-Field Anomalies in the Io Plasma Torus: Evidence for Interchange in the Io Plasma Torus?, Geophys. Res. Lett., 24, p2127, 1997(C) [KIVELSONETAL1998A] Kivelson et al, Ganymede's Magnetosphere: Magnetometer Overview, J. Geophys Res, 03, p19963, 1998(A)  [KHURANA1997] Khurana, K. K., Euler potential models of Jupiter's magnetospheric field, J. Geophys Res., 102, p11295, 1997 [KHURANAETAL1997A] Khurana et al, No Intrinsic Field Associated with Callisto, Nature, 387, p262, 1997(A) [KHURANAETAL1997B] Khurana et at, Interaction of Io with its torus: Does Io have an internal magnetic field?, Geophys. Res. Lett., 24, p2127, 1997(B)

Confidence Level Overview :  These are raw data as supplied by the project to the magnetometer team. This data set is archived for completeness and is not likely to be useful to most users. Users of the data should be cautious, particularly regarding the time tags associated with the vectors. Substantial processing is required to convert this data set into the standard products provided by the magnetometer team.   Data Coverage and Quality :  Data Gaps:  There are numerous gaps in the MAG data for a variety of reasons. These include packets lost during telemetry (station outages, cross-overs, etc.), instrument misconfiguration, instrument and spacecraft anomalies, insufficient downlink, superior conjunctions, and being deselected from the downlink as the result of bits being traded to other instruments or working groups. The following is a list of major outages during the prime mission orbital operations:  Orbit gap start gap end reason ------------------------------------------------------------------ G1 96-200 96-204 instrument incorrectly configured G1 96-204 96-222 instrument flip anomaly G1 96-238 96-247 spacecraft safing J5 97-015 97-020 superior conjunction J5 97-021 97-048 instrument anomaly - single event upset E6 97-048 97-059 instrument anomaly - E6 encounter lost G7 97-118 97-124 instrument flip anomaly J13 98-017 98-062 superior conjunction  No attempt has been made to document the reason for data losses of less than a day.