Magnetometer (MAG)
Galileo Orbiter at Jupiter Calibrated High Resolution readme
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Brief Bundle Description
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This bundle 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. These data were acquired in the optimal
averager (opt/avg) and real-time survey (RTS) modes beginning during
the Jupiter approach and continuing throughout Jupiter orbital
operations. 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.
Sampling rates are variable and depended upon the
downlink capabilities. With few exceptions, the data are provided at
the full downlink resolution. The data are provided in five
coordinate systems (IRC, System III [1965], JSE, JSO, and JSM).
All data files are stored in the 'data' branch of the directory tree. Each
instrument is given a subdirectory and each bundle is located in a
subdirectory beneath that. Most data are stored in ASCII tables although
some binary data are also included. All files give time values in Spacecraft
Event Time (SCET). Some files may give an additional time column that
contains the Earth Received Time (ERT) in addition to the SCET.
Users of these data are encouraged to acknowledge both the PDS and the
principal investigators of the instruments whose data is used in analysis
in all publications.
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Bundle Information
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This data was previously released as PDS3 data from part of the Galileo
Magnetospheric Working Group Jupiter Science data sets. These PDS3 data
sets include the following:
* GODDS_9001 - Galileo Oribiter Dust Detection System bundle
* GOEPD_9001 - Galileo Orbiter at Jupiter EPD High-Res. Sectored bundle
* GOEPD_9002 - Galileo Orbiter at Jupiter EPD Scan Averages bundle
* GOHIC_9001 - Galileo Orbiter at Jupiter HIC High-Res. Energetic Ion
Countrates bundle
* GOHIC_9002 - Galileo Orbiter at Jupiter HIC Real-time Science (Low Rate)
Energetic Ion Countrates bundle
* GOHIC_9003 - Galileo Orbiter at Jupiter HIC Ion Flux Composition bundle
* GOMAG_9001 - Galileo Orbiter at Jupiter MAG High-Res. Magnetic-Field bundle
* GOMAG_9002 - Galielo Orbiter at Jupiter MAG Survey (Low Rate) Magnetic-
Field bundle
* GOPLS_9001 - Galileo Orbiter at Jupiter PLS Full-Res. Raw bundle
* GOPLS_9002 - Galileo Orbiter at Jupiter PLS Spin Averaged Countrates bundle
* GOPOS_9001 - Galileo Orbiter at Jupiter Spacecraft Trajectory in Jupiter-
Centered Coordinates bundle
* GOPOS_9002 - Galileo Orbiter at Jupiter Spacecraft Trajectory in Jovian
Moon-Centered Coordinates bundle
* GOPOS_9003 - Galileo Orbiter at Jupiter Jovian Moon Trajectories in
Jupiter-Centered Coordinates bundle
* GOPOS_9004 - Galileo Orbiter at Jupiter Rotor Attitude bundle
* GOPWS_9001 - Galileo Orbiter at Jupiter PWS 1 Min. Averaged Electric &
Magnetic Wave Spectra bundle
* GOPWS_9002 - Galileo Orbiter at Jupiter PWS Full-Res. Electric & Magnetic
Wave Spectra bundle
* GOPWS_9003 - Galileo Orbiter at Jupiter PWS Full-Res. (RTS Mode) Electric
& Magnetic Wave Spectra bundle
* GOPWS_9004 - Galileo Orbiter at Jupiter PWS 1 kHz Wideband Waveform bundle
* GOPWS_9005 - Galileo Orbiter at Jupiter PWS 10 kHz Wideband Waveform bundle
* GOPWS_9006 - Galileo Orbiter at Jupiter PWS 80 kHz Wideband Waveform bundle
* GORSS_9001 - Galileo Orbiter Jupiter and Io RSS Radio Occulation
Ionospheric Electron Density Profiles bundle
* GOSSD_9001 - Galileo Orbiter at Jupiter SSD Derived Electron Flux bundle
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Mission Facts
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The Galileo spacecraft and some science instruments were reprogrammed after
arrival at Jupiter so that data acquisition and downlink could be achieved
at the low bit rates associated with the mission after the high gain antenna
(HGA) anomaly. New software was telemetered to the spacecraft in early May 1996
in a period known as the 'Inflight Load' or IFL. The mission prior to the IFL
is known as the Phase 1 mission. After the IFL the mission is referred to as
the Phase 2 mission. In Phase 1 raw data were provided to the instrument
teams in Experiment Data Record (EDR) format. In Phase 2, the whole
telemetry stream and ground data system were changed. The raw data were
'packetized' and delivered electronically as packet files or instrument
packet files (IPF). The difference between a packet file and an IPF is a
single 44 byte header called an SFDU. The Io data stored on this Bundle were
acquired during Phase 1 and downlinked after the IFL by use of the new
capabilities of the Phase 2 flight software. As such, they are a hybrid form
of data that were acquired by using flight software that may differ from
other files of the same raw data format. This is primarily of concern when
instrument reprogramming has resulted in a change in the contents of the raw
data (i.e. MAG).
The Galileo orbits were named by concatenating the first letter of the name
of the primary target in each orbit with the orbit number. Thus, the fourth
Jupiter orbit, in which Europa is the primary target, is called E4. The
project defined orbits according to spacecraft command load boundaries rather
than the normal convention of apoapsis to apoapsis. The navigation team did
not always adhere to this convention, causing some confusion. The PDS has
organized the data and data delivery schedules around the project defined
orbit boundaries. The following tables contain information about the orbital
tour and satellite encounters:
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Galileo Orbit Information
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Orbit Orbit ❮--- Periapsis Info ----❯ ❮-- Apoapsis Info --❯
Num Start Periapsis Range Local Apoapsis Range Local
Date Date/Time ❮Rj**❯ Time Date ❮Rj❯ Time
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J0 95-12-03 95-12-07 21:54 4.00 16:21 96-03-29 267.7 03:39
G1 96-06-23 96-06-28 00:31 11.03 15:36 96-08-09 125.3 03:24
G2 96-09-01 96-09-07 13:38 10.65 15:22 96-10-07 113.0 03:12
C3 96-11-02 96-11-06 13:31 9.21 15:34 96-11-27 89.1 03:28
E4 96-12-15 96-12-19 03:22 9.16 15:21 97-01-04 72.1 03:00
J5* 97-01-15 97-01-20 00:26 9.05 14:54 97-02-04 72.1 02:48
E6 97-02-16 97-02-20 20:55 9.12 14:28 97-03-14 89.2 02:20
G7 97-03-30 97-04-04 11:03 9.12 14:14 97-04-21 75.9 01:56
G8 97-05-04 97-05-08 11:42 9.27 13:29 97-06-02 100.2 01:21
C9 97-06-22 97-06-27 11:52 10.77 12:35 97-08-08 143.0 00:21
C10 97-09-14 97-09-18 23:10 9.17 12:44 97-10-13 98.9 00:36
E11 97-11-02 97-11-06 23:02 9.03 12:36 97-11-26 84.1 00:29
E12 97-12-15 97-12-16 06:35 8.80 12:29 97-12-20 46.6 00:37
J13* 98-02-09 98-02-10 23:09 8.85 12:33 98-03-06 95.2 00:25
E14 98-03-28 98-03-29 07:59 8.83 12:17 98-04-30 199.7 00:16
E15 98-05-30 98-06-01 02:34 8.85 12:12 98-06-26 100.4 00:03
E16 98-07-20 98-07-20 17:18 9.93 11:54 98-08-23 124.4 23:51
E17 98-09-25 98-09-26 08:26 8.91 11:44 98-10-24 110.4 23:34
E18 98-11-21 98-11-22 03:57 9.23 11:24 98-12-27 129.0 23:17
E19 99-01-31 99-02-01 02:38 9.24 10:56 99-03-18 154.3 22:40
C20 99-05-02 99-05-03 17:00 9.37 10:24 99-06-02 114.5 21:46
C21 99-06-29 99-07-02 05:04 7.27 10:04 99-07-22 89.0 21:57
C22 99-08-11 99-08-12 10:58 7.32 09:50 99-08-29 77.1 21:23
C23 99-09-13 99-09-14 19:57 6.55 09:17 99-09-27 65.7 20:46
I24 99-10-10 99-10-11 03:31 5.68 08:41 99-11-01 97.7 20:47
I25 99-11-25 99-11-26 23:30 5.94 08:39 99-12-15 87.2 20:28
E26 00-01-01 00-01-04 03:33 5.78 08:14 00-01-28 102.7 20:05
I27 00-02-20 00-02-22 12:30 5.85 07:56 00-04-06 154.4 19:55
G28 00-05-17 00-05-21 04:52 6.68 07:18 00-09-08 289.9 18:37
G29 00-12-27 00-12-29 03:26 7.49 06:03 01-03-11 216.3 17:37
C30 01-05-07 01-05-23 17:33 7.28 05:11 01-06-29 136.8 16:27
I31 01-08-04 01-08-06 04:52 5.93 04:14 01-09-10 132.2 16:05
I32 01-10-14 01-10-15 23:56 5.78 03:53 01-12-01 160.7 15:39
I33 02-01-16 02-01-17 16:23 5.54 03:13 02-06-13 348.1 14:21
A34 02-11-04 02-11-05 07:23 1.99 01:40 03-04-14 336.7 12:49
J35 03-09-21 03-09-21 18: 1.00
* Solar Conjunction - no data from this orbit
** Rj = 71492 km
Satellite Flyby Characteristics*
Satellite Planetocentric Coords
Range Lat E Lon
Orb Moon C/A Time (Rm**) (deg) (deg) Note
------------------------------------------------------------
0 IO 95-12-07 17:45:58 1.50 -9.6 258.9 W
24 IO 99-10-11 04:33:03 1.34 4.5 135.9 U
27 IO 00-02-22 13:46:41 1.11 18.5 157.4 U
31 IO 01-08-06 04:59:21 1.11 77.5 187.7 P
32 IO 01-10-16 01:23:21 1.10 -78.5 135.3 P
33 IO 02-01-17 14:08:28 1.06 -43.5 41.8 F
4 EUR 96-12-19 06:52:58 1.45 -1.7 322.4 F
6 EUR 97-02-20 17:06:10 1.38 -17.0 34.7 F
11 EUR 97-11-06 20:31:44 2.31 25.7 218.7 F
12 EUR 97-12-16 12:03:20 1.13 -8.7 134.4 U
14 EUR 98-03-29 13:21:05 2.06 12.2 131.2 U
15 EUR 98-05-31 21:12:57 2.62 15.0 225.4 W
19 EUR 99-02-01 02:19:50 1.93 30.5 28.1 U
26 EUR 00-01-03 17:59:43 1.22 -47.1 83.4 U
1 GAN 96-06-27 06:29:07 1.32 30.4 246.7 W
2 GAN 96-09-06 18:59:34 1.10 79.3 236.4 P
7 GAN 97-04-05 07:09:58 2.18 55.8 270.4 W
8 GAN 97-05-07 15:56:10 1.61 28.3 84.8 U
28 GAN 00-05-20 10:10:10 1.31 -19.0 92.4 U
29 GAN 00-12-28 08:25:27 1.89 62.2 269.0 P
3 CALL 96-11-04 13:34:28 1.47 13.2 282.3 W
9 CALL 97-06-25 13:47:50 1.17 2.0 101.0 U
10 CALL 97-09-17 00:18:55 1.22 4.6 281.3 W
30 CALL 01-05-25 11:23:58 1.06 13.6 254.6 W
34 AMA 02-11-05 06:18:40 2.89 -47.7 74.8 U
* Satellite encounters with recorded data only
J2000 reference, body fixed spherical coordinates.
** Moon Rm (km)
=======================
Amalthea 86.2
Io 1818
Europa 1560
Ganymede 2634
Callisto 2409
Notes: Negative latitudes are southern hemisphere,
U = upstream
F = flank
W = wake
P = polar
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).
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Table 1. MAG High-Resolution Observation Coverage
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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 ❮units❯
------------------------------------------------------------------
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 ❮nT❯
By_sc float Y field component in IRC coordinates ❮nT❯
Bz_sc float Z field component in IRC coordinates ❮nT❯
|B| float Field magnitude ❮nT❯
rotattr float Rotor right ascension (EME-50) ❮degrees❯
rotattd float Rotor declination (EME-50) ❮degrees❯
rotattt float Rotor spin phase angle (EME-50) ❮degrees❯
spinangl float Rotor spin phase angle (ECL-50) ❮degrees❯
------------------------------------------------------------------
System III [1965] Coordinates
------------------------------------------------------------------
Column Type Description ❮units❯
------------------------------------------------------------------
time char Spacecraft event time, PDS time format
Br float Radial field component ❮nT❯
Btheta float Southward field component ❮nT❯
Bphi float Eastward field component ❮nT❯
|B| float Field magnitude ❮nT❯
Range float Range from Jupiter to Galileo ❮Rj=71492 km❯
LAT float Planetocentric latitude of spacecraft ❮degrees❯
ELON float Jovian east longitude of spacecraft ❮degrees❯
WLON float Jovian west longitude of spacecraft ❮degrees❯
------------------------------------------------------------------
Satellite Centered 'Planetocentric' Coordinates (SPRH)
------------------------------------------------------------------
Column Type Description ❮units❯
------------------------------------------------------------------
time char Spacecraft event time, PDS time format
Br float Radial field component ❮nT❯
Btheta float Polar field component, positive northward ❮nT❯
Bphi float Azimuthal field component ❮nT❯
|B| float Field magnitude ❮nT❯
Range float S/C distance from satellite ❮Rmoon❯
LAT float S/C 'planetocentric' latitude ❮degrees❯
LON float S/C 'planetocentric' longitude ❮degrees❯
------------------------------------------------------------------
Satellite centered Phi-Omega Coordinates (PhiO)
------------------------------------------------------------------
Column Type Description ❮units❯
------------------------------------------------------------------
time char Spacecraft event time, PDS time format
Bx float Corrotational B-field component ❮nT❯
By float Jupiterward B-field component ❮nT❯
Bz float Northward B-field component ❮nT❯
|B| float Field magnitude ❮nT❯
X float corrotational component of S/C position wrt
satellite ❮Rmoon❯
Y float Jupiterward component of S/C position ❮Rmoon❯
Z float Northward component of S/C position ❮Rmoon❯
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 bundle 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 bundle,
they are ancillary to this bundle.
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 ❮degrees❯
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 bundle 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 bundle. 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 bundle 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.
============================================================================
Contacts
============================================================================
For questions or problems regarding this archive, please contact the PDS/PPI
PDS operator:
Email pds_operator@igpp.ucla.edu
Telephone (310) 206-6073
|