| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This dataset includes the Galileo Orbiter Solid State Imaging data on the
asteroid 243 Ida. The raw data have already been archived in PDS with the
data set name 'Galileo Imaging (SSI) Asteroid, Earth and Moon Experiment
Data Records' and can be found by searching on the data set identification
'GO-A/E-SSI-2-REDR-V1.0'. Only those images in which Ida actually appears
have been included here. Images in both FITS and ISIS Cube format are
provided.
Processing of the ISIS Cube Format Files
========================================
The raw images were converted from VICAR format to FITS format using the
image reduction package IRAF. The image prefix tables, telemetry tables,
and bad data value headers were removed from the raw images. All relevant
label keywords describing the image have been retained in the raw image
labels.
The images in this archive were converted from FITS format to ISIS cube
format using GLLSSI2ISIS, and radiometrically calibrated using GLLSSICAL.
GLLSSICAL was the tool provided in the original, raw data delivery for
calibration of Galileo SSI images. GLLSSI2ISIS inputs were the raw image
file name and the output image file name for the ISIS format image.
GLLSSICAL inputs were image file name in the ISIS format created by
GLLSSI2ISIS, units = IOF, scale=1. The GLLSSICAL output was the file name
for the radiometrically calibrated image in ISIS cube format.
Description of the ISIS software can be found in:
Anderson, J.A., 2008. ISIS camera model design, 39th LPSC (Houston), p.
Abstract #2159, Lunar and Planetary Institute.
Anderson, J.A., Sides, S.C., Sotesz, D.L., Sucharski, T.L., Beker, K.J.,
2004. Modernization of the integrated software for imagers and
spectrometers, 35th LPSC (Houston), p. Abstract #2039, Lunar and Planetary
Institute.
Processing of the FITS Format Files
===================================
The raw images were converted from VICAR format to FITS format using the
image reduction package IRAF. The image prefix tables, telemetry tables,
and bad data value headers were removed from the raw images. All relevant
label keywords describing the image have been retained in the raw image
labels.
The images in this archive were converted from FITS format to ISIS cube
format using GLLSSI2ISIS, and radiometrically calibrated using GLLSSICAL.
GLLSSICAL was the tool provided in the original, raw data delivery for
calibration of Galileo SSI images. GLLSSI2ISIS inputs were the raw image
file name and the output image file name for the ISIS format image.
GLLSSICAL inputs were image file name in the ISIS format created by
GLLSSI2ISIS, units = IOF, scale=1. The GLLSSICAL output was the file name
for the radiometrically calibrated image in ISIS cube format. The
radiometrically calibrated ISIS cube format images were converted to FITS
format using the ISIS routine ISIS2FITS. ISIS2FITS inputs were the
radiometrically calibrated image file name (in ISIS cube format),
bittype=32, minpercent=0.5, maxpercent=99.5, info=Nominal (nominal fits
header). The ISIS2FITS output was the radiometrically calibrated image in
FITS format.
Description of the ISIS software can be found in:
Anderson, J.A., Sides, S.C., Sotesz, D.L., Sucharski, T.L., Beker, K.J.,
2004. Modernization of the integrated software for imagers and
spectrometers, 35th LPSC (Houston), p. Abstract #2039, Lunar and Planetary
Institute.
Radiometric Calibration Description
===================================
The GLLSSICAL program performs the following processing steps on each pixel:
1. The radiometric correction is applied:
e = z(d - dc)
where:
z is retrieved from the Radiometric File.
d is the DN.
dc is retrieved from the Dark-Current File.
2. The output pixel is scaled to I/F using the following equation:
S1 K
r = e * -------- * --- (D/5.2)2
A1(t-to) Ko
where:
S1 = filter-dependent conversion factor from ft-Lamberts to I/F
units for a reference distance of 5.2 AU from the Sun.
A1 = output picture scale factor.
t = commanded exposure time of the input image(msec).
to = line-dependent shutter offset.
K = system gain constant for the gain-state of the image.
Ko = system gain constant for the calibration file gain-state.
D = target distance from the Sun (in AU).
The output DN is usually in the range of 0.0 to 1.0. If the uneven bit
weighting correction is enabled, the input DN values (d) will be corrected
for uneven-bit-weighting due to the ADC. If the input dark-current file is
in byte format (i.e. an individual dark-current frame), then the correction
will be applied to the dark-current as well. The current correction table
was supplied by Herb Breneman, 2 Mar 89, and is based on 1975 calibration
data. This application outputs LRS for any negative I/F values that are
encountered.
Data
====
The data are included in a series of files with filenames of the form
*rcal_XXX.FIT, where * denotes the spacecraft clock start count, rcal
denotes the image has been radiometrically calibrated, and XXX denotes the
filter name where:
Filter Name XXX
CLEAR clr
RED red
GREEN gre
VIOLET vio
IR-7560 ir7
IR-8890 ir8
IR-9680 ir9
The filename of the original, raw files were the last four digits of the
spacecraft clock start count.
The general table, color-set_id.tab, denotes which images were acquired at
similar viewing conditions but in separate filters, thus constituting a
color image set. The table includes image file name, filter name, and a
designator for which color set the image belongs. Images with the same
designator value (A-F) belong to the same color image set.
Filter response curves taken from Klaasen et al. 1997 are included in the
document directory.
Both FITS and CUBE files are 2.6MB in size, giving 169MB each for the FITS
and CUBE file subdirectories. The corresponding image labels are 4 KB each,
giving 260KB each for the label subdirectories.
K.P. Klaasen, M.J.S. Belton, H.H. Brenenman, A.S. McEwen, M.E. Davies, R.J.
Sullivan, C.R. Clark, G. Neukum, C.M. Heffernan, A.P. Harch, J.M. Kaufman,
W.J. Merline, L.R. Gaddis, W.F. Cunningham, P. Helfenstein, T.R. Colvin.
Inflight performance characteristics, calibration, and utilization of the
Galileo solid-state imaging camera, Opt. Eng.36(11) 3001-3027 (November
1997).
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