Data Set Overview : This data set contains high time resolution magnetic field vectors acquired by the Galileo magnetometer (MAG). It includes both satellite flyby and non-flyby data. These data were acquired in order to characterize various portions of the Jovian magnetosphere at high time resolution. The Galileo Magnetospheres Working Group (MWG) collectively acquired high time resolution data for short intervals in order to try and regain some of the magnetospheric science lost due to the low data rates of the phase 2 mission (no high gain antenna) mission. These observations are scattered in Jovian distance, local time, System III longitude, etc. in order to provide some insight into processes that may be active in different regions of the magnetosphere. There were a few orbits in which MAG obtained high-resolution coverage in conjunction with remote sensing (typically NIMS) observations. Regular MWG high-resolution observations were recorded to tape using the 7.68 bits/second Low-Rate Science and Plasma Wave (LPW) tape mode. Observations using higher tape speed modes included recorded LPW rate data as well. In cases where the coverage provided was adequate, and when there was sufficient bits-to-ground (BTG) allocation to return them, these 'ridealong' observations provided coverage in addition to the regular MWG observations. A list of ridealong recordings is provided in the 'Data Coverage and Quality' section of this document. Satellite Flybys: One of the primary objectives of the Galileo mission was to characterize the magnetic signatures of Jupiter's Galilean satellites, determine their sources, and study their interactions with the Jovian system. In particular, confirming the presence of a sub-surface ocean on Europa became a major focus of the Europa Mission (GEM). The Millennium Mission (GMM) also included a flyby of Amalthea. Inner Magnetosphere: Characterizing the Io torus was a high priority goal of the MWG throughout the mission. In order to protect the spacecraft and instrument from the high radiation of the inner magnetosphere, most of the inner magnetosphere observations were deferred until late in GEM and GMM. Middle Magnetosphere: In the middle magnetosphere, a variety of observations were made in order to characterize the distribution of plasma in the plasma sheet and to examine the regions where field lines likely map to the auroral oval. Magnetotail: Another of the MWG high priority science objectives was to study the structure of the Jovian magnetotail. Orbit C09 was specifically designed to meet this objective. Apojove was near 150 Rj at local midnight. High time resolution data was acquired for five intervals at various distances and local times. Table 1. gives information on the coverage provided by the various MAG high time resolution observations. In addition to start time and duration, the table describes the minimum and maximum distance from the spacecraft to Jupiter, and the local hour and Sys. 3 west longitude (WLON) of the spacecraft at the beginning and end of the recorded interval. Local hour is given in terms of decimal hours (0.0-23.9). WLON is in units of degrees (0-359). ------------------------------------------------------------------ Table 1. MAG High-Resolution Observation Coverage ------------------------------------------------------------------ Io Flybys: ------------------------------------------------------------------ Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ------------------------------------------------------------------ I00-IO 95-12-07 15:21 184 5.4- 7.7 10.6-12.3 204-290 I24-IO 99-10-11 03:42 66 5.7- 6.0 10.1-10.9 59- 87 3 I25-IO N/A 1 I27-IO 00-02-22 13:04 81 5.9- 6.0 8.4- 9.4 64- 97 3 I31-IO 01-08-06 04:25 63 5.9 3.9- 4.7 145-171 I32-IO 01-10-16 01:06 73 5.9- 6.1 4.8- 5.7 253-283 I33-IO N/A 1 Europa Flybys: ------------------------------------------------------------------ Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ------------------------------------------------------------------ E04-EUR 96-12-19 06:33 51 9.4- 9.5 16.6-16.9 147-173 E06-EUR 97-02-20 16:37 312 9.5- 9.1 12.8-14.8 326-125 2 E11-EUR 97-11-06 20:09 162 9.0- 9.4 10.8-11.9 211-294 E12-EUR 97-12-16 11:42 46 9.4- 9.6 14.5-14.8 107-131 7 E14-EUR 98-03-29 13:05 55 9.4- 9.6 14.3-14.7 176-204 E15-EUR 98-05-31 20:42 61 9.4- 9.6 9.9-10.3 277-308 E16-EUR N/A 1 E17-EUR 98-09-26 03:54 N/A 9.4 9.9 140 6 E18-EUR N/A 1 E19-EUR 99-02-01 01:49 50 9.2- 9.4 9.7-10.0 245-270 I25-EUR 99-11-25 16:29 N/A 9.5 3.2 196 6 E26-EUR 00-01-03 17:29 61 9.2- 9.7 2.8- 3.1 346- 18 Ganymede Flybys: ------------------------------------------------------------------ Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ------------------------------------------------------------------ G01-GAN 96-06-27 06:07 45 14.9-15.1 11.2-11.3 163-188 G02-GAN 96-09-06 18:32 56 14.8-15.2 10.7-10.9 143-174 G07-GAN 97-04-05 06:44 56 14.8-15.2 19.7-19.8 5- 37 G08-GAN 97-05-07 15:36 46 14.8-15.1 8.1- 8.2 276-302 C09-GAN 97-06-26 17:20 N/A 15.2 8.0 301 6 E12-GAN 97-12-15 09:58 N/A 15.0 6.7 10 6 G28-GAN 00-05-20 09:40 61 14.7-15.3 0.7- 0.8 334- 9 G29-GAN 00-12-28 07:54 61 14.7-15.3 23.9-24.0 203-238 Callisto Flybys: ------------------------------------------------------------------ Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ------------------------------------------------------------------ C03-CALL 96-11-04 13:15 45 26.1-26.4 7.8 231-258 C09-CALL 97-06-25 13:25 46 26.1-26.4 5.5 47- 74 C10-CALL 97-09-16 23:49 60 26.0-26.4 5.0- 5.1 318-354 C20-CALL 99-05-05 13:56 N/A 26.2 17.8 53 6,9 C21-CALL 99-06-30 07:47 N/A 26.2 1.8 316 6 C22-CALL 99-08-14 08:31 N/A 26.3 18.1 27 6 C23-CALL 99-09-16 17:27 N/A 26.2 17.9 279 6 C30-CALL 01-05-25 11:09 35 26.2-26.5 13.1-13.2 68- 89 Amalthea Flyby: ------------------------------------------------------------------ Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ------------------------------------------------------------------ A34-AMA 02-11-05 05:45 50 2.3- 3.1 20.8-22.7 147-148 8 Inner Magnetosphere: ------------------------------------------------------------------ Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ------------------------------------------------------------------ J00-PJOV 95-12-07 23:22 124 4.0- 5.2 18.4-20.5 18- 62 I24-TOR N/A 1 I32-TOR 01-10-15 22:55 33 5.8- 5.9 3.0- 3.4 198-211 I27-TOR 00-02-22 10:22 113 5.9- 6.1 6.3- 7.7 357- 44 I25-TOR 99-11-25 21:07 174 5.9- 7.0 5.1- 7.0 336- 53 3 A34-PSX7 02-11-05 01:05 280 3.1- 7.7 17.7-20.8 24-147 C23-PJOV 99-09-14 14:36 412 6.5- 7.7 6.1-10.3 52-239 C21-PJOV 99-07-01 23:53 113 7.6- 8.2 7.4- 8.3 247-301 C22-PJOV 99-08-12 08:18 288 7.3- 7.6 8.4-11.0 225- 0 E11-EQX (see E11 EUR) 4 I32-RAMP 01-10-15 15:31 115 7.8-8.9 22.9-23.7 354- 52 C10-EQX 97-09-18 22:34 46 9.2 12.5-12.8 102-125 C20-PJOV 99-05-03 15:59 122 9.4 10.0-10.8 45-106 A34-PSX6 02-11-04 21:48 45 10.3 17.0-17.1 285-300 Middle Magnetosphere: ----------------------------------------------------------------- Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ----------------------------------------------------------------- C09-TAR 97-06-28 13:50 61 18.1-18.5 18.1-18.2 324-359 C03-TAR 96-11-05 07:04 40 19.3-19.0 8.9- 9.0 140-163 5 G08-QRS 97-05-06 13:00 129 25.0-25.8 5.9- 6.0 63-140 G01-PSX 96-06-30 02:00 46 27.2-27.5 22.8 292-319 A34-PSX2 02-11-03 15:28 45 29.4-29.0 15.6 276-303 A34-PSX1 02-11-03 10:38 45 31.8-31.4 15.5 102-132 G02-PSX 96-09-11 02:38 40 39.2-39.4 23.8-23.9 121-145 G07-PSX 97-03-30 18:49 46 46.2-46.4 4.8 125-152 Magnetotail: ----------------------------------------------------------------- Dur. Jup Range Local Time S3 WLON Obs. ID* Start Time (min) (Rj) (hours) (deg). Note ----------------------------------------------------------------- C09-DSK1 97-07-04 14:09 118 64.3-64.8 22.1 99-170 C09-DSK2 97-07-14 10:03 45 107 23.2 357- 25 E18-DSK 98-12-10 19:36 288 109 22.5 285- 98 C09-DSK3 97-07-23 13:11 46 129 23.7 18- 45 C09-DAWN 97-08-23 14:07 122 130 0.9- 1.0 17- 90 C09-APJ 97-08-07 11:06 101 143 0.3 30- 91 * The ID element is derived from the SEF identifier for the recorded observation. The recording identifiers translate to: IO, GAN, EUR, CALL, AMA - satellites PSX - plasma sheet crossing TAR - trans-auroral region QRS - quarter rotation survey DSK - dusk side of orbit (see local time) DAWN - dawn side of orbit (see local time) APJ - apojove TOR - Io plasma torus EQX - magnetic equator crossing PJOV - perijove RAMP - outer Io plasma torus (ramp region) These designations were defined by the sequence team. Notes: 1 : Recording lost due to spacecraft safing/anomaly 2 : Recording lost due to instrument anomaly 3 : Stats given for primary observation interval only, data file includes additional intervals of 'ridealong' data 4 : E11-EUR and EQU are continuous and listed as a single observation 5 : Due to bit-to-ground limitations the C03 TAR observation was not returned in order to provide continuous low rate (RTS) MAG coverage 6 : No high-resolution data coverage for this flyby - RTS rate coverage only (time and position information are for closest approach) 7 : E12-EUR data were corrupted due to instrument saturation have been 'recovered' (see 'Limitations' for information on the recovery process) 8 : A34-AMA data corrupted due to instrument saturation; release of data delayed pending development of new saturation recovery software and techniques 9 : Flyby occurs in gap in coverage Table 2 provides a listing of the various satellite closest approach times and the location of the spacecraft, relative to the satellite at these times. ------------------------------------------------------------ Table 2. Satellite Flyby Characteristics ------------------------------------------------------------ Satellite Planetocentric Coords Orb Moon C/A Time Range(Rm*) Lat(deg) Lon(deg) ------------------------------------------------------------ 0 IO 95-12-07 17:45:58 1.50 -9.6 258.9 24 IO 99-10-11 04:33:03 1.34 4.5 135.9 27 IO 00-02-22 13:46:41 1.11 18.5 157.4 31 IO 01-08-06 04:59:20 1.11 77.5 187.7 32 IO 01-10-16 01:23:21 1.10 -78.6 135.2 33 IO 02-01-17 14:08:28 1.06 -43.5 41.8 4 EUR 96-12-19 06:52:58 1.45 -1.7 322.4 6 EUR 97-02-20 17:06:10 1.38 -17.0 34.7 11 EUR 97-11-06 20:31:44 2.31 25.7 218.7 12 EUR 97-12-16 12:03:20 1.13 -8.7 134.4 14 EUR 98-03-29 13:21:05 2.06 12.2 131.2 15 EUR 98-05-31 21:12:57 2.62 15.0 225.4 17 EUR 98-09-26 03:54:20 3.30 -42.4 220.2 19 EUR 99-02-01 02:19:50 1.93 30.5 28.1 25 EUR 99-11-25 16:29:05 6.54 62.3 266.0 26 EUR 00-01-03 17:59:43 1.22 -47.1 83.4 1 GAN 96-06-27 06:29:07 1.32 30.4 246.7 2 GAN 96-09-06 18:59:34 1.10 79.3 236.4 7 GAN 97-04-05 07:09:58 2.18 55.8 270.4 8 GAN 97-05-07 15:56:10 1.61 28.3 84.8 9 GAN 97-06-26 17:19:35 31.27 0.0 261.2 12 GAN 97-12-15 09:58:09 6.47 -5.8 266.1 28 GAN 00-05-20 10:10:10 1.31 -19.0 92.4 29 GAN 00-12-28 08:25:27 1.89 62.2 269.0 3 CALL 96-11-04 13:34:28 1.47 13.2 282.3 9 CALL 97-06-25 13:47:50 1.17 2.0 101.0 20 CALL 99-05-05 13:56:18 1.55 2.8 258.3 21 CALL 99-06-30 07:46:50 1.43 -0.7 268.0 22 CALL 99-08-14 08:30:52 1.95 -2.3 252.5 23 CALL 99-09-16 17:27:02 1.43 0.1 249.7 10 CALL 97-09-17 00:18:55 1.22 4.6 281.3 30 CALL 01-05-25 11:23:58 1.06 13.6 254.6 34 AMA 02-11-05 06:18:43 2.56 -45.4 68.3 * Rm : Moon radii, please refer to Table 4 for a listing of the radii of Jupiter's moons Processing : The processing of MAG data is performed as a series of operations on the data. 1) Extract raw MAG and Attitude and Articulation and Control System (AACS) data from the packetized telemetry files. Set sample time tags, sort data on time, and remove duplicate samples. 2) Remove the calibration estimate applied by the instrument. This involves multiplying the data by the inverse of the onboard geometry matrix, dividing by gain factors, and adding offsets to the data. This returns the data to sensor coordinates. 3) Apply post orbit inflight calibration (scale to nT, subtract offsets, multiply by coupling matrix). This properly orients the data in the spinning spacecraft reference frame. 4) Merge in the AACS data, interpolate to MAG sample times, correct the phase angle for phase delays in the instrument and despin the data into IRC coordinates. 5) Transform data into geophysical coordinates using SPICE based software and SPICE kernels. Parameters : Data Sampling ------------- The magnetometer samples the field thirty times per second. These data are recursively filtered and decimated down to a sample rate of two vectors per minor frame (mf : 2/3 second) before being recorded to tape in LPW format. For all orbits except G01 and G02, the MAG data are evenly sampled in time, 3 samples per second. Due to an instrument programming error that occurred during the instrument reprogramming for phase 2 operations, the G01 and G02 LPW data are unevenly sampled in time within the minor frames. Each minor frame consists of 10 real-time interrupts (RTI). In the G01 and G02 data, the mid minor frame sample occurs half an RTI later than it should. This problem was corrected before the C03 orbit. All data are time stamped with universal time (UT) at the spacecraft when the instrument sampled data within the recursive filter. MAG uses fixed gains to acquire data [KIVELSONETAL1992]. Gain states must be manually changed by sending a gain change command to the instrument. There are 3 ranges of field strengths that the instrument can measure: ---------------------------------------------------------------- Table 3. Magnetometer Ranges ---------------------------------------------------------------- Field Range (nT) Magnetometer, field range min max ---------------------------------------------------------------- 1/64 - 32 Outboard low field 1/4 - 512 Outboard high field, Inboard low field 8 - 16384 Inboard high field Recursive filtering of LPW data makes the apparent digitization step size much smaller than it appears in Table 3. Variation in the vector field components attributable to the spacecraft spin reduces the effective digitization levels in the filtered data to about one quarter of the A/D step size. The outboard magnetometer, low field mode was used to acquire data beyond 60 Rj and the inboard magnetometer, high field mode was used to acquire data inside of 9 Rj. During the prime mission, the both the inboard low field and the outboard high field modes were used to acquire data between 9-60 Rj. As the outboard magnetometer is further out from the main body of the spacecraft on the boom than the inboard magnetometer it is impacted less by spacecraft fields. For this reason it was initially preferred over the inboard magnetometer. However, the outboard magnetometer began to experience abrupt changes in the sensor zero levels towards the end of the prime mission. As a result, the inboard magnetometer, low field mode was used to acquire data between 9-60 Rj throughout the remainder of the mission. Data : The data are provided in four (4) coordinate systems (IRC, System III, satellite centered 'planetographic', and Phi-Omega). For moon flybys, data are provided all four of these coordinate systems. For non-flyby observations only IRC and System III coordinates are provided. Data from each coordinate system are stored in separate files with simple ASCII table formats. The structure and contents of the data files are described below. The coordinate systems are described later in this document in the section entitled 'Coordinate Systems.' Data file structures -------------------- ------------------------------------------------------------------ IRC Coordinates (despun spacecraft coordinates) ------------------------------------------------------------------ Column Type Description  ------------------------------------------------------------------ time char Spacecraft event time, PDS time format sclk char Spacecraft clock (rim:mf:mod10:mod8) Bx_sc float X field component in IRC coordinates  By_sc float Y field component in IRC coordinates  Bz_sc float Z field component in IRC coordinates  |B| float Field magnitude  rotattr float Rotor right ascension (EME-50)  rotattd float Rotor declination (EME-50)  rotattt float Rotor spin phase angle (EME-50)  spinangl float Rotor spin phase angle (ECL-50)  ------------------------------------------------------------------ System III [1965] Coordinates ------------------------------------------------------------------ Column Type Description  ------------------------------------------------------------------ time char Spacecraft event time, PDS time format Br float Radial field component  Btheta float Southward field component  Bphi float Eastward field component  |B| float Field magnitude  Range float Range from Jupiter to Galileo  LAT float Planetocentric latitude of spacecraft  ELON float Jovian east longitude of spacecraft  WLON float Jovian west longitude of spacecraft  ------------------------------------------------------------------ Satellite Centered 'Planetocentric' Coordinates (SPRH) ------------------------------------------------------------------ Column Type Description  ------------------------------------------------------------------ time char Spacecraft event time, PDS time format Br float Radial field component  Btheta float Polar field component, positive northward  Bphi float Azimuthal field component  |B| float Field magnitude  Range float S/C distance from satellite  LAT float S/C 'planetocentric' latitude  LON float S/C 'planetocentric' longitude  ------------------------------------------------------------------ Satellite centered Phi-Omega Coordinates (PhiO) ------------------------------------------------------------------ Column Type Description  ------------------------------------------------------------------ time char Spacecraft event time, PDS time format Bx float Corrotational B-field component  By float Jupiterward B-field component  Bz float Northward B-field component  |B| float Field magnitude  X float corrotational component of S/C position wrt satellite  Y float Jupiterward component of S/C position  Z float Northward component of S/C position  These data were processed using 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 Ancillary Data : There are several files that are provided in addition to the data files themselves that may be of value to the user. These include a table of important spacecraft and instrument events including onboard calibration parameters, an instrument calibration table, a description of instrument anomalies and resolutions, and a set of quick-look or 'browse' plots of the data. Due to bit rate limitations some of the targetted satellite flybys had no high-resolution recordings associated with them. For these and a few distant flybys data are provided in satellite-centered coordinates at the RTS data rate. Included are Europa flybys in E19 and I25, Ganymede flybys in C9 and E12, and Callisto flybys in C21, C22, and C23. The C20 Callisto flyby was lost due to a telemetry outage. While these data are part of Survey Data Set, they are ancillary to this data set. Coordinate Systems : The data are provided in four coordinate systems. Data are provided in the spacecraft coordinate system in order to aid in the interpretation of particle instrument data. The other three coordinate systems provided for use in Jovian magnetospheric studies. Inertial Rotor Coordinates (IRC) -------------------------------- The IRC coordinate system takes the basic rotor coordinate system (Y along the boom, Z opposite the high gain antenna) which is spinning, and despins it using the rotor spin angle. For this reason IRC coordinates are sometimes referred to as 'despun spacecraft coordinates.' In this system, Z still points along the spin axis opposite the HGA (or roughly anti-Earthward), X is approximately parallel to the downward ecliptic normal, and Y completes the right-handed set (pointing roughly towards dawn). System III [1965] Coordinates (SYS3) ------------------------------------ System III [1965] (SYS3) magnetic field vector components form the standard right-handed spherical triad (R, Theta, Phi) for a Jupiter centered system. Namely, R is radial (along the line from the center of Jupiter to the center of the spacecraft), and positive away from Jupiter. Phi, the azimuthal component, is parallel to the Jovigraphic equator (Omega x R) and positive in the direction of corotation. Theta, the 'southward' component, completes the right-handed set. For SYS3 trajectory both east and west longitudes are provided. West longitudes are related to east longitudes by to the algorithm: west longitude : 360. - east longitude  West longitude is defined such that it appears to increase with time for a stationary observer [DESSLER1983]. Note, however, that R, latitude, and west longitude constitute a left handed set. The SYS3 1965 prime meridian is the sub-Earth longitude of 1965-01-01 00:00 UT. The spin rate (which was determined from the rotation rate of the magnetic field) is 9 hrs 55 min 29.719 sec. (See [DESSLER1983] for a discussion on Jovian longitude). R is the radial (Jupiter's center to spacecraft center) distance. Latitude is planetocentric. Satellite-Centered Planetographic (Right Handed) Coordinates (SPRH) ------------------------------------------------------------------- SPRH is a spherical 'planetocentric' coordinate system, centered at the satellite. The magnetic field components are the standard right-handed spherical triad: R, Theta, and Phi. R is radial (along the line from the center of the satellite to the center of the spacecraft), and positive away from the satellite. Phi, the azimuthal component, is parallel to the satellite's planetographic equator (Omega x R) and positive in a right-handed sense. Theta, the 'southward' component, completes the right-handed set. Trajectory components are also right-handed. Since all of the satellites studied are nearly phase locked to Jupiter, the SPRH prime meridian is effectively the sub-Jupiter meridian. More precise definitions are provided by the IAU [1994] (see Table 4). Longitude is measured from the prime meridian and is positive in a right-handed sense (see figure below). R is the radial distance (satellite's center to spacecraft center). Latitude is planetocentric. --------------------------------------------------------------- Table 4. IAU 1994 Satellite Information (all angles in degrees) --------------------------------------------------------------- Pole Orientation Prime Rotation Rt. Radius Moon r.a. dec. Meridian (deg/24 hrs) (km) --------------------------------------------------------------- Amalthea 268.05 +64.49 231.67 +722.6314560 86.2 Io 268.05 +64.50 200.39 +203.4889538 1818 Europa 268.08 +64.51 35.67 +101.3747235 1560 Ganymede 268.20 +64.57 44.04 +50.3176081 2634 Callisto 268.72 +64.83 259.67 +21.5710715 2409 SPRH longitudes: 90 | 180 -- Sat -- 0 --> to Jupiter | 270 Satellite Phi-Omega Coordinates (PHIO) -------------------------------------- The PhiO (Satellite Phi:X, Omega:Z) fixed coordinate system is defined by using the two vectors Phi, the corotation velocity vector at the satellite, and Omega, the Jovian spin axis. Phi is positive in the direction of corotation and Omega is positive northward. Y completes the right-handed set (pointing towards Jupiter). The basis vectors of the coordinate system are fixed at the epoch time (satellite closest approach, see Table 2). The spacecraft trajectory information takes the instantaneous range vector (R) from the satellite center to the spacecraft and resolves it into XYZ components. Ranges are given in units of satellite radii (see Table 4).

Review : These data have been reviewed by the instrument team and are of the highest quality that can be generated at this time. Science results based on some of these data have been published in several journals (Science, JGR, etc.). After submission to PDS, these data successfully completed the peer review process. Data Coverage and Quality : This data set contains the high time resolution magnetometer data. The data are highly discontinuous due to bit rate limitations of the spacecraft. High time resolution data could only be acquired over brief intervals in each orbit and never for more than a few hours at a time. Individual recorded intervals are provided in separate files. While every attempt has been made to insure that the data within each observation are complete and as gap-free as possible, some gaps still do exist. The most common causes for these are communication outages between the spacecraft and the Galileo ground system, and data corruption due to spikes or MAG calibration exercises. A listing of the larger gaps and their causes (if known) is provided in the MAG gap listing file that is associated with this data set. More data coverage information (including information for scheduled observations for which there was no MAG coverage) is provided in Table 1 above. The data quality is variable. This data set spans the entire mission and contains data segments recorded in many different instrument modes. Both calibration and digitization step size vary from mode to mode and observation to observation. Information regarding instrument mode and calibration used for particular observations is provided in the MAG high-resolution data calibration file. As mentioned above, there were a few orbits in which MAG was able extend it's coverage with ridealong recordings. A list of these ridealong recordings is given in Table 5 below. --------------------------------------------------------------- Table 5. MAG Ridealong Observations --------------------------------------------------------------- Obs. ID Start Time Stop Time Prim. Inst. --------------------------------------------------------------- I24-IO 1999-10-11 04:51:11 1999-10-11 06:41:51 NIMS I25-TOR 1999-11-26 04:42:42 1999-11-26 05:54:37 NIMS I27-IO 2000-02-22 14:16:55 2000-02-22 14:25:41 NIMS I32-IO 2001-10-16 01:56:12 2001-10-16 02:21:47 NIMS Product Versions : The following table describes the various versions of the data files. -------------------------------------------------------------------- Product Version ID Description -------------------------------------------------------------------- 1 original release 2 SYS3 coordinate file was modified to include both east and west longitude columns; a variety of changes were made to record formats Limitations : Signals at the spin period (~19 seconds) or its higher order harmonics are most likely instrumental. The primary source of field uncertainty is in the sensor offsets (zero levels plus s/c field). Incorrect zero levels appear as a DC shift in the spin aligned sensor, and first harmonic of the spin period in the spin plane sensors. Incorrect removal of the spacecraft field appears as first harmonic in the spin aligned sensor, and higher order harmonics in the spin plane sensors. Spin plane field components are reliable to better than 1/4 of the digitization step size of each mode. The uncertainty in the spin axis component is probably between 1/3 and 1/2 the digitization step size. While the resulting uncertainty is >.1 nT for most modes, the large digitization step size of the inboard high field modes can result in spin tones of above 1 nT. In addition to the more general limitations, the following apply to individual orbits or observations. Obs. ID Limitation -------- -------------------------------------------------------- G01-GAN/ Data are unevenly sampled in time. Caution must be used G01-PSX/ when analyzing the spectra. G02-GAN/ G02-PSX C03-CALL The data for this observation are NOT well calibrated. The magnetometer sensors appear to have failed to lock into place correctly. As a result the calibration appears to be changing. This anomaly reduces the confidence in the sensor geometry on the order of a degree or two. There are of course still the common errors associated sensor zero levels and quantization. In order to minimize the effects of these uncertainties, the data have been averaged to two seconds using a centered 20 second averaging window. The net error in the average is on the order of a few tenths of a nanoTesla per component. As a side effect of the averaging all of the higher frequency signals have been eliminated. E12-EUR Due to unexpectedly large magnetic field strength, some of the magnetometer data was corrupted due to instrument saturation. The problem occurs 1997-Dec-16 11:53:00 - 12:05:20. The corrupted data have been recovered by identifying the bad data in the spinning reference frame, then simultaneously fitting a sine and cosine to the remaining data to reproduce the spinning signature. Note that this technique only recovers oscillations with frequencies lower than the spin frequency. For more information on the recovery process refer to the file /CALIB/MAG/MAG_SATURATION.TXT. C21-PJOV/ The AACS data for these recordings were seriously C22-PJOV/ corrupted and required special processing to correct. C23-PJOV The rotor twist, and spin angles were corrected by discarding the LPW rate data, and interpolating the RTS rate data. Rotor right ascension (RA) and declination (DEC) have been handled differently in each case. For C21-PJOV RA and DEC have been set to a fixed value. For C22-PJOV RA and DEC have been restricted to a limited set of the most common values. For C23-PJOV the LPW rate values have been discarded and the RTS rate data has been interpolated. While the corrections to the AACS appear to have improved the quality of the MAG data, some uncertainty still exists. In particular a few clear problems are still evident in the spin plane components of the magnetic field (the x and y components in despun spacecraft coordinates) of C21-PJOV. Special care should be taken in the use of all of these data. Please note, however, that as the field magnitude may be treated with much less suspicion than the field components, as the magnitude is unaffected by changes in the spacecraft attitude. A34-PSX7/ The AACS data for this recording was seriously corrupted A34-AMA and required special processing to correct. The rotor twist and spin angles were corrected by first correcting the 'rotor spin delta' which was downlinked from the spacecraft. The spin delta was corrected by setting bad values to within 0.0002 radians (1 DN) of the average. This new spin delta was then used to regenerate the rotor twist and spin angles. The RA and DEC were corrected by removing spikes and interpolating the between the remaining good points. As with other data with corrected AACS, the corrections appear to have improved the quality of the MAG data, but some uncertainty still exists. Special care should be taken in the use of these data. The field magnitude may be treated with much less suspicion than the field components, as the magnitude is unaffected by changes in the spacecraft attitude. A34-AMA As anticipated the MAG instrument saturated during the A34-AMA recording period. A special matrix (without crossterms) was used to prevent cross-contamination of one sensor due to saturation in another sensor. However, due to the rapidly increasing field strength through this observation the saturation recovery method used at E12-EUR was inadequate. To obtain these data please contact the instrument team.