PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
DATA_SET_ID = "GO-J-MAG-3-RDR-HIGHRES-V1.0"
PRODUCT_ID = "MAG_CALIB_HIGHRES"
PRODUCT_TYPE = "DOCUMENT"
PRODUCT_VERSION_ID = "1"
PRODUCT_CREATION_TIME = 2003-03-07
START_TIME = 1995-12-07T15:30
STOP_TIME = 2003-11-05T05:45
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", "AMALTHEA"}
INSTRUMENT_NAME = "TRIAXIAL FLUXGATE MAGNETOMETER"
INSTRUMENT_ID = "MAG"
^ASCII_DOCUMENT = "MAG_CALIB_HIGHRES.TXT"
OBJECT = ASCII_DOCUMENT
DOCUMENT_NAME = "
GALILEO MAGNETOMETER LPW DATA CALIBRATION DESCRIPTION"
PUBLICATION_DATE = 2004-10-29
DOCUMENT_TOPIC_TYPE = "CALIBRATION DESCRIPTION"
INTERCHANGE_FORMAT = ASCII
DOCUMENT_FORMAT = TEXT
DESCRIPTION = "
This document includes the calibration matrices used in the processing
of the high resolution Galileo magnetometer data. The full calibration
process, including the application and derivation of the calibration
matrices is described."
END_OBJECT = ASCII_DOCUMENT
END
Overview
========
GALILEO MAGNETOMETER LPW DATA CALIBRATION DESCRIPTION
The following calibrations were used in the ground processing of the
data. For information on the onboard gains, offsets, and matrices
please see the MAG EVENTS table in this directory.
The Galileo Magnetometer must apply a calibration and 'despinning' algorithm
to the raw data in order to be able to produce non-zero averages of the
field in the optimal averager and RTS modes. A calibration consists of a
zero level (offset) correction, sensor gain correction, and an
orthogonalization matrix that aligns the sensors with spinning rotor
coordinate system.
Each component of the calibration is time variable. Sensor zero levels have
the greatest time variability. The sensor zero levels have two components:
electronics and spacecraft field. Galileo is a highly complex spacecraft.
Spacecraft fields are observed at the first 3 spacecraft spin harmonics and
at the frequency of the EPD stepping motor. The electronics component of the
zero levels was observed to have a large temperature dependence in the
Earth-Jupiter cruise phase. These changes stopped when the temperature
normalized to the jovian environment. There are still aging effects in the
electronics. The sensor gains have been quite stable but some variation is
indicated. The boom geometry also appears to be stable. The onboard
calibration parameters used are the best values available when the orbit
command sequence is being designed. These values are always improved in post
processing. This file provides the data necessary to post-process the data.
The first task in post-processing is removing the onboard processing. The
onboard processing parameters are stored in the MAG_EVENTS tables. The
following lines have been extracted from ORB00_MAG_EVENT.TAB:
INBRD_SENSOR_ON 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
INBRD_SENSOR_HI 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
DML:4E80(????) 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
SCALE:0002 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
CONST/CTL:0200_0001 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
GAINS:3F60_411E_405B 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
OFF:004B_0003_004B 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
MAT_1:00AA_8002_F8E7 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
MAT_2:7FFD_009A_FF65 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
MAT_3:0038_F90F_7FFD 95-12-07/13:30:54 9.151 -2.574 147.032 9.971 SYS3
The onboard parameters are provided in HEX, where individual components are
separated by underscores. The HEX should be converted first to integers (DN),
and then to floating point numbers. Convert DN to nT by dividing DNs by
the mode scale factor. Multiply the observed field vector by the inverse of
the onboard orthogonalization matrix to get the data back to sensor coords.
Then divide by the floating point gain factors and add back the offsets.
The offset/gain values are given in the order: sensor 1, sensor 2, sensor 3.
Using the naming conventions and scale factors described below, we find, for
example, that the gain for sensor 1 is 3F60 = 16224 = 0.99613 and the offset
for sensor 1 in ILHR mode is 004B = 75 = 37.5. Once this process is
performed, the data are in sensor coordinates and units and are ready to
have the calibration applied.
The calibration technique that is used for inflight calibrations is
described by KEPKOETAL1996. This is a spectral method that does not
distinguish between gains and geometry when computing the coupling matrix.
To apply the new calibration, multiply by the coupling matrix to get the data
into rotor coordinates, i.e:
Rotor Coords Coupling Matrix sensor coords/units
[m11 m12 m13] [s1]
(Bx',By',Bz') = |m21 m22 m23| * |s2|
[m31 m32 m33] [s3]
The primes indicate that the process is not yet complete. To complete the
process, offsets must be subtracted. The spin aligned sensor offsets (Oz)*
are provided with the coupling matrices below. The spin plane sensor offsets
(Ox, Oy) should be computed by taking integral spin period averages of the
spin plane components in spinning rotor coordinates. The next step is to
remove the offsets from the values:
Bx = Bx' = Ox; By = By' - Oy; Bz = Bz' - Oz;
The final steps involve despinning the data and transforming the data to
geophysically meaningful coordinate systems.
* The spin aligned sensor offset must be determined by using other techniques.
Mode Naming
===========
Each instrument mode has its own calibration. The instrument has two sensor
triads (Inboard and Outboard). Each sensor has two possible orientations or
flip states (Left, Right) and two fixed gain states (high gain = low field
and vise versa). Mode names are constructed to describe the instrument state
in the order above using:
U/I = Outboard or Inboard
L/R = Left or Right flip position
LR/HR = Low range (high gain) or High Range
(i.e. ILLR = Inboard sensor, flip left, low range). Please refer to
KIVELSONETAL1992 for additional details about the instrument (available in
the DOCUMENT/MAG directory).
Scale Factors (DN to nT conversions)
====================================
Orthogonalization Matrix 1 nT = 32678 DN
Gains 1 nT = 16384 DN
Mag Vectors and Offsets
IxHR 1 nT = 2 DN
IxLR, UxHR 1 nT = 64 DN
UxLR 1 nT = 1024 DN
MAG Calibration Parameters for High-Resolution MAG Data
=======================================================
Whenever possible the same calibration has been used in ground processing for
all recordings in a given mode. It was not, however, always possible to find
a single calibration which worked for each mode. The below table contains a
listing of all of the recordings for which there is high-resolution MAG data.
The table includes the recording ID and date, instrument mode used, a
calibration ID, and finally the total z-sensor offset. Calibration ID's
follow the naming used during MAG data processing. They are provided here in
order to identify the orthogonality matrix that has been applied to the data.
The orthogonality matrix elements for each calibration identified in this
table are given below. The total z-sensor offset is the full zero-level
correction applied to the raw, uncorrected MAG data. Unlike the lower
resolution data, with LPW data it is possible to remove the effects of the
onboard zero-level correction so that the full correction may be determined.
---------------------------------------------------------------
Table 1. MAG High-Res. Observation Calibration Information
---------------------------------------------------------------
Obs. ID Date Mode Calibration ID Z-Offset Note
---------------------------------------------------------------
I00-IO 1995-12-07 ILHR CD96152 (ILHRK1) 37.5 a
G01-GAN 1996-06-27 ILLR ILLR02 5.96
G01-PSX 1996-06-30 ILLR ILLR02 5.96
G02-GAN 1996-09-06 ILLR ILLR02 6.26
1996-09-06 ILHR ILHR03 41.5 b
G02-PSX 1996-09-11 ILLR ILLR02 4.06
C03-CALL 1996-11-04 IRLR IRLR_C3_U3 -0.85
E04-EUR 1996-12-19 ILHR ILHR03 37.5
G07-PSX 1997-03-30 ILLR ILLR02 5.06
G07-GAN 1997-04-05 ILLR CD97014 (ILLRK1) 6.06
G08-QRS 1997-05-06 IRLR CD99283 (IRLRK1) -1.55
G08-GAN 1997-05-07 IRLR CD99283 (IRLRK1) -1.55
C09-CALL 1997-06-25 IRLR IRLR03 -2.05
C09-TAR 1997-06-28 IRLR IRLR03 -4.05
C09-DSK1 1997-07-04 URLR URLR01 -1.40
C09-DSK2 1997-07-14 URLR URLR01 -0.50
C09-DSK3 1997-07-23 URLR URLR01 -0.50
C09-APJ 1997-08-07 URLR URLR01 -0.33
C09-DAWN 1997-08-23 URLR URLR01 -0.30
C10-CALL 1997-09-17 IRLR IRLR03 -2.65
C10-EQU 1997-09-18 IRLR IRLR03 -2.65
E11-EUR 1997-11-06 ILLR ILLRE2 5.96 c
E12-EUR 1997-12-03 ILLR ILLRE2 7.56
E14-EUR 1998-03-29 ILLR ILLRE2 6.46
E15-EUR 1998-05-31 ILLR ILLR02 6.36
E18-PSX 1998-12-10 ILLR ILLR02 6.96
E19-EUR 1999-02-01 ILLR ILLRE19_01 6.56
C20-PJOV 1999-05-03 ILLR ILLRC20_03 7.26
C21-PJOV 1999-07-01 ILHR ILHRC21_01 44.5
C22-PJOV 1999-08-12 ILHR ILHR03 47.0
C23-PJOV 1999-09-14 ILHR ILHR03 46.5
I24-TOR 1999-10-11 ILHR ILHRI24_01 48.5
I25-TOR 1999-11-25 ILHR ILHRI25_01 44.0
E26-EUR 2000-01-03 ILLR E26_ILLR03 8.06
ILHR E26_ILHR03 47.5 d
I27-TOR 2000-02-22 ILHR ILHRI25_01 47.5
I27-IO 2000-02-22 ILHR ILHRA34_01 47.5
G28-GAN 2000-05-20 ILLR ILLRE2 7.66
G29-GAN 2000-12-28 ILLR ILLRG28_02 7.66
C30-CALL 2001-05-25 ILLR ILLR02 7.51
I31-IO 2001-08-06 ILHR ILHR03 46.7
I32-RAMP 2001-10-15 ILHR ILHRA34_01 49.0
I32-TOR 2001-10-15 ILHR ILHRI32_03 47.5
I32-IO 2001-10-16 ILHR ILHRI32_03 49.0
A34-PSX02 2002-11-03 ILLR ILLR02 7.66
A34-PSX06 2002-11-04 ILLR ILLRG28_02 7.56
A34-PSX07 2002-11-05 ILHR ILHRI32_03 47.5 e
ILHR ILHRA34_01 47.5
A34-AMA 2002-11-05 ILHR
NOTES:
a - J0 PSX/IO used fixed spin plane offsets of Ox=-3.5 and Oy=41.2
b,d - G02-GAN and E26-EUR both contained mode changes during the
recording. As a result, both the ILLR and ILHR modes were used.
c - E11-EUR and E11-EQU were contiguous in time
e - A34-PSX07 has been processed using two different calibrations.
ILHRI32_03 has been used in the lower field region (where
time<2002-11-05 04:47:00), and ILHRA34_01 was used for the
higher field data (time>2002-11-05 04:47:00).
ILHR CALIBRATIONS
-----------------
calibration ID = CD96152 (ILHRK1)
matrix (nT) = 0.005252 -1.017174 -0.060191
0.984121 0.004677 -0.003778
0.000425 -0.060009 1.005252
calibration ID = ILRH03
matrix (nT) = 0.005267 -1.017428 -0.055148
0.986150 0.004557 -0.002166
-0.000532 -0.055533 1.005540
calibration ID = ILHRC21_01
matrix (nT) = 0.005267 -1.017428 -0.055148
0.986150 0.004557 -0.002166
-0.001174 -0.055571 1.006531
calibration ID = ILHRI24_01
matrix (nT) = 0.005256 -1.017486 -0.042983
0.985401 0.004540 -0.008211
-0.000530 -0.055864 1.006213
calibration ID = ILHRI25_01
matrix (nT) = 0.005267 -1.017433 -0.055329
0.986147 0.004644 -0.003147
-0.000544 -0.055434 1.005531
calibration ID = E26_ILHR03
matrix (nT) = 0.005267 -1.017428 -0.055148
0.986150 0.004557 -0.002166
-0.001174 -0.055571 1.006531
calibration ID = ILHRI32_03
matrix (nT) = 0.005266 -1.017464 -0.050153
0.986816 0.005319 -0.004621
-0.000532 -0.055533 1.005540
calibration ID = ILHRA34_01
matrix (nT) = 0.005266 -1.017464 -0.050153
0.986816 0.005319 -0.004621
-0.000499 -0.054972 1.005812
ILLR CALIBRATIONS
-----------------
calibration ID = ILLR02
matrix (nT) = 0.000026 -1.023087 -0.053138
0.997765 -0.000314 -0.003210
-0.000494 -0.055493 1.000596
calibration ID = ILLRE2
matrix (nT) = 0.000014 -1.023067 -0.051872
0.997064 -0.000198 -0.005052
-0.000272 -0.055929 1.000666
calibration ID = CD97014 (ILLRK1)
matrix (nT) = 0.000044 -1.022816 -0.056685
0.995676 0.003413 -0.003878
-0.000775 -0.060309 1.000405
calibration ID = ILLRE19_01
matrix (nT) = 0.000028 -1.023156 -0.056342
0.998263 -0.000215 -0.001755
-0.000503 -0.054302 1.000425
calibration ID = ILLRC20_03
matrix (nT) = 0.000026 -1.023124 -0.054113
0.998382 -0.000161 -0.003587
-0.000474 -0.054790 1.000544
calibration ID = E26_ILLR03
matrix (nT) = 0.000093 -1.023111 -0.064281
0.999541 -0.001156 0.008344
-0.000547 -0.055863 1.000241
calibration ID = ILLRG28_02
matrix (nT) = 0.000015 -1.023039 -0.051904
0.999684 0.000701 -0.006010
-0.000289 -0.056462 1.000666
IRLR CALIBRATIONS
-----------------
calibration ID = IRLR03
matrix (nT) = 0.000061 -0.030480 1.007506
1.000231 -0.005611 -0.004512
0.004580 1.006979 0.034500
calibration ID = IRLR_C3_U3
matrix (nT) = 0.000079 -0.037425 1.006929
0.996820 -0.002932 -0.004407
0.003249 1.007320 0.071185
calibration ID = CD99283 (IRLRK1)
matrix (nT) = -0.000044 -0.055709 1.007506
1.000231 0.001140 -0.005265
0.004418 1.005933 0.052680
URLR CALIBRATIONS
-----------------
calibration ID = URLR01
matrix (nT) = 0.000676 -0.126145 0.967596
0.972320 -0.002783 -0.005939
-0.005257 0.974088 0.098940
REFERENCES
==========
KEPKOETAL1996 Kepko, E.L., K.K. Khurana, M.G. Kivelson, R.C. Elphic,
and C.T. Russell, Accurate Determination of Magnetic
Field Gradients from Four Point Vector Measurements --
Part I: Use of Natural Constraints on Vector Data
Obtained From a Single Spinning Spacecraft, IEEE Trans.
on Magnetics, 32, 2, P. 377-385, 1996.
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.