PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
DATA_SET_ID = "GO-J-MAG-3-RDR-MAGSPHERIC-SURVEY-V1.0"
PRODUCT_ID = "MAG_CALIB_SURVEY"
PRODUCT_TYPE = "DOCUMENT"
PRODUCT_VERSION_ID = "1"
PRODUCT_CREATION_TIME = 2003-03-07
START_TIME = 1995-11-02T00:00
STOP_TIME = 2003-09-21T18:00
INSTRUMENT_HOST_NAME = "GALILEO ORBITER"
INSTRUMENT_HOST_ID = "GO"
MISSION_PHASE_NAME = "JUPITER ORBIT OPERATIONS"
TARGET_NAME = {"JUPITER", "IO", "IO PLASMA TORUS", "EUROPA",
"GANYMEDE", "CALLISTO"}
INSTRUMENT_NAME = "TRIAXIAL FLUXGATE MAGNETOMETER"
INSTRUMENT_ID = "MAG"
^ASCII_DOCUMENT = "MAG_CALIB_SURVEY.TXT"
OBJECT = ASCII_DOCUMENT
DOCUMENT_NAME = "
GALILEO MAGNETOMETER SURVEY DATA CALIBRATION DESCRIPTION"
PUBLICATION_DATE = 2003-03-07
DOCUMENT_TOPIC_TYPE = "CALIBRATION DESCRIPTION"
INTERCHANGE_FORMAT = ASCII
DOCUMENT_FORMAT = TEXT
DESCRIPTION = "
This document describes the processing of the Galileo Magnetometer
Real-Time Science (RTS) and Optimal Averager magnetospheric survey
data. Included is a time history of the spin-aligned sensor delta
offset."
END_OBJECT = ASCII_DOCUMENT
END
Overview
========
GALILEO MAGNETOMETER SURVEY DATA CALIBRATION DESCRIPTION
This file describes the calibration techniques used in the ground processing
of the real-time (RTS) and optimal averager (OPT AVG) data. Unlike the high
resolution (LPW) data, was not possible to remove the affects of the
calibration that was applied to the data onboard the spacecraft. The only
calibration that may be applied on the ground were 'delta offsets,' or
corrections on top of the offsets applied in the onboard processing. For
information on the onboard gains, offsets, and matrices please see the
MAG event tables.
Ground processing for RTS data consisted of the following steps:
1) apply scale factors
2) respin the data using the rotor spin angle
3) calculate the offsets in the spin plane sensors using running averages
of the data over an integral number of spin periods
4) subtract spin plane offsets
5) despin the data using the spin angle
6) subtract spin aligned sensor offset
The spin plane sensor offsets were effectively eliminated in the OPT AVG data
by the long averaging intervals used. As a result the only improvement
possible for those data was a correction of the spin aligned offset.
Mode Naming
===========
The instrument had two sensor triads designated the inboard and outboard
magnetometers. Each triad had two possible orientations or 'flip states'
(left or right) and two fixed gain states (high gain=low field,
low gain=high field). The instrument configuration (or mode) was identified
according to the following convention:
MORR
where:
M - magnetometer ('U'=outboard, 'I'=inboard)
O - flip state ('L'=left, 'R'=right)
RR - gain state ('LR'=low range/high gain, 'HR'=high range/low gain)
(e.g. ILLR = inboard magnetometer, flip left, low range).
Please refer to KIVELSONETAL1992 for additional details about the instrument.
Scale Factors (DN to nT conversions)
====================================
Mag Vectors and Offsets
IxHR 1 nT = 2 DN
IxLR, UxHR 1 nT = 64 DN
UxLR 1 nT = 1024 DN
MAG Calibration Parameters for RTS and OPT AVG MAG Data
=======================================================
Offsets of the spin plane sensors were determined using running averages of
the re-spun data. As a result, was not practical to provide their time
history. Spin aligned offsets, however, were much more constant. The spin
aligned offsets varied between instrument modes due to differences in the
configuration of the instrument sensors. In addition, the zero level of
individual sensors were observed to have drifted over time. The outboard
magnetometer proved particularly unstable. In the outboard magnetometer there
were a number of anomalous steps of several nanoTesla observed.
Table 1 contains a time history of the z-sensor zero level offsets applied in
ground processing. Note that the z-offsets given in this table are 'delta
z-offsets' and may not match the 'total z-offsets' given for high-resolution
data at the same time. The difference is that the offset applied onboard has
been removed before calculating the total z-offsets in the high-resolution
data. With the RTS and OPT AVG data, on the other hand, the offsets applied
in the onboard processing could not be removed, so the offset calculated for
these data is a 'delta' applied to the onboard offset.
Changes in the z-sensor offsets used typically coincided with instrument mode
changes. Changes within a single mode may be due to the offset used in the
onboard data processing. There were also a number of anomalous jumps in
offset that occurred over the course of the mission. This offset anomalies
occurred almost exclusively in the outboard magnetometer (specifically in the
URLR mode). The reason for these offsets is unclear, though it is worthy
noting that operating temperatures at Jupiter were well below the design
minimums for the magnetometer, and may have played a role in the zero-level
instability. Mode changes of brief (<2 hours) duration (typically used for
calibration purposes) are not included on this list. This table also lists
several a few of the larger data gaps over which it was not possible to
determine the correct offset. For more information on MAG gaps please see the
MAG gap listing.
---------------------------------------------------------------------------
Table 1. Spin-axis (spacecraft z-sensor) offsets
---------------------------------------------------------------------------
Orb Start Time Mode Z-Offset Notes
---------------------------------------------------------------------------
01 96-06-23/16:01 ILLR 0.75
01 96-07-05/02:44 URLR 0.0
01 96-07-13/10:14 ULLR -0.75
01 96-07-21/23:37 URLR N/A data gap (instrument anomaly)
01 96-08-09/04:39 ULLR -0.75
01 96-08-24/14:27 N/A N/A data gap (spacecraft safing)
01 96-08-31/11:16 ILLR 1.5 onboard offset changed from last ILLR
02 96-09-01/16:05 ULLR -0.75
02 96-09-01/19:47 ILLR 1.5
02 96-09-06/18:51 ILHR N/A simulated RTS generated from high-res
02 96-09-06/19:08 ILLR 1.5
02 96-09-14/07:45 ULLR -0.75
02 96-10-14/11:00 URLR -1.5
02 96-10-14/12:00 ULLR -0.75
02 96-10-29/18:14 IRLR 1.5
03 96-11-06/11:00 IRHR 1.5
03 96-11-06/18:00 IRLR 1.5
03 96-11-11/02:03 URLR -1.5
03 96-11-11/02:50 IRLR 1.5
03 96-11-14/00:59 URLR -0.35
03 96-11-22/15:13 ULLR 0.0
03 96-12-01/00:13 URLR -0.35
03 96-12-11/20:46 N/A N/A data gap (instrument anomaly)
04 96-12-15/00:05 ILLR 0.55
04 96-12-18/22:52 ILHR 2.0
04 96-12-19/09:18 ILLR 0.55
04 96-12-29/21:10 URLR -1.6
04 97-01-11/13:38 N/A N/A data gap (solar conj./inst. anomaly)
06 97-02-28/09:28 ULHR -0.2
06 97-03-02/07:25 ULLR -0.55
06 97-03-03/19:10 URLR -0.35
06 97-03-26/16:49 ULLR -0.55
06 97-03-28/06:50 ULHR -0.2
07 97-03-30/16:05 ILLR 0.2
07 97-04-04/06:10 ILHR 0.0
07 97-04-04/16:20 ILLR 1.2
07 97-04-12/07:00 URLR -0.7
07 97-04-16/15:19 URLR -3.7 offset anomaly
07 97-04-27/19:19 ILLR N/A data gap (instrument anomaly)
08 97-05-06/09:02 IRLR -0.3
08 97-05-08/07:01 IRHR 0.0
08 97-05-08/16:51 IRLR -0.3
08 97-05-11/17:00 URHR -2.5
08 97-05-15/15:06 URLR -3.4
08 97-06-20/16:36 IRLR -0.3
09 97-06-22/16:05 IRLR 0.35
09 97-06-24/04:52 IRLR 2.7 onboard offset changed from last IRLR
09 97-06-29/16:05 URHR 0.4
09 97-07-02/10:00 URLR -1.75
09 97-07-09/23:41 URLR 2.0 onboard offset changed from last URLR
09 97-08-05/04:54 URLR 1.1 onboard offset changed from last URLR
09 97-09-12/13:00 IRLR 0.0 onboard offset changed from last IRLR
10 97-09-15/23:51 IRLR 2.5 onboard offset changed from last IRLR
10 97-09-19/18:32 URHR -0.4
10 97-09-25/19:38 URLR -1.5
10 97-10-05/14:53 URLR 0.0
10 97-10-05/16:10 URLR 1.75 offset anomaly
10 97-10-06/15:30 URLR 0.25 offset anomaly
10 97-10-31/05:40 ILLR 1.0
12 97-12-15/08:00 ILLR 2.0
12 97-12-16/02:00 ILHR 7.0
12 97-12-16/10:20 ILLR 2.0
12 97-12-20/17:50 N/A N/A data gap (spacecraft anomaly)
13 98-02-12/02:35 N/A N/A data gap (solar conjunction)
13 98-03-25/05:54 ILLR 2.7
14 98-03-29/06:20 ILHR 4.0
14 98-03-29/12:30 ILLR 2.7
15 98-06-01/00:15 ILHR 7.0
15 98-06-01/06:16 ILLR 2.7
16 98-07-20/17:18 N/A N/A data gap (spacecraft anomaly)
16 98-07-24/15:13 ILLR 3.0
17 98-09-26/04:43 ILHR 7.0
17 98-09-26/09:25 ILLR 3.0
20 99-05-02/17:00 ILLR 3.3
21 99-07-01/20:46 ILHR 7.0
21 99-07-02/12:40 ILLR 3.3
22 99-08-12/02:56 ILHR 10.0
22 99-08-12/19:01 ILLR 3.5
23 99-09-14/11:31 ILHR 9.0
23 99-09-15/04:24 ILLR 3.5
24 99-10-11/03:30 ILHR 10.0
24 99-10-11/11:10 ILLR 3.95
25 99-11-25/16:49 ILHR 10.0
25 99-11-26/11:00 ILLR 4.1
26 00-01-01/23:30 ILLR 4.3
26 00-01-03/18:23 ILHR 10.0
26 00-01-04/13:10 ILLR 4.3
27 00-02-20/04:00 ILLR 3.95
27 00-02-22/03:17 ILHR 10.0
27 00-02-22/21:14 ILLR 3.95
27 00-04-05/16:25 URLR 2.0
27 00-04-06/04:17 ILLR 3.95
28 00-05-20/20:58 ILHR 10.0
28 00-05-21/12:41 ILLR 3.95
28 00-05-26/13:00 URLR 1.3
28 00-12-23/16:30 ILLR 3.95
29 00-12-28/20:53 ILHR 10.0
29 00-12-29/09:59 ILLR 3.95
29 01-01-03/17:40 URLR 1.3
29 01-02-07/06:11 URLR -1.1 offset anomaly (offset drifts linearly
from -1.1 to -0.7 at the mode change)
29 01-05-15/03:55 ILLR 3.95
30 01-05-23/10:37 ILHR 10.0
30 01-05-24/00:21 ILLR 3.95
30 01-05-29/14:00 URLR 1.3
30 01-07-31/09:00 ILLR 3.95
31 01-08-05/20:27 ILHR 10.0
31 01-08-06/13:49 ILLR 3.95
31 01-08-12/02:30 URLR 0.1
31 01-09-12/08:00 URLR -1.8 offset anomaly
31 01-10-10/03:00 ILLR 3.95
32 01-10-15/15:24 ILHR 10.0
32 01-10-16/08:45 ILLR 3.95
32 01-10-21/15:30 URLR 0.3
32 02-01-12/02:00 ILLR 3.95
33 02-01-17/07:43 ILHR 10.0
33 02-01-18/04:23 ILLR 3.95
33 02-01-22/20:30 URLR 0.5
33 02-10-31/12:30 ILLR 3.95
34 02-11-04/23:34 ILHR 10.0
34 02-11-05/05:45 ILHR
34 02-11-08/13:44 ILLR 3.95
34 02-11-13/15:05 URLR 1.3
34 03-01-13/04:14 N/A N/A data gap (nominal end of operations)
35 03-09-21/07:10 ILLR 3.95
35 03-09-21/11:16 ILHR 10.0 end of data 03-09-21/17:33
REFERENCES
==========
KIVELSONETAL1992 Kivelson M.G., K.K. Khurana, J.D. Means, C.T. Russell,
and R.C. Snare, The Galileo Magnetic Field
Investigation, Space Science Rev., 60, P. 357, 1992.