DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains images of the Saturn system taken by the
Wide Field/Planetary Camera 2 (WFPC2) aboard the Hubble Space
Telescope (HST) through November 1995. This period includes all
images taken during the Saturn ring plane crossings of 1995. (No
WFPC2 images of Saturn were obtained during the last ring plane
crossing in February 1996 because Saturn was too close to the
Sun.)
Every WFPC2 image showing Saturn, its rings or the region of the
inner satellites has been included in this data set, regardless of
the original intended purpose. Note that some images were not
specifically intended for ring or inner satellite observations and
so are not optimally exposed for this use.
The HST observing programs whose results are included in this
data set are as follows:
Proposal: 5219
Title: Saturn's Aurora, Airglow, and Extended Atmosphere
PI: John Trauger (Jet Propulsion Laboratory)
Proposal: 5508
Title: Tracking Features in Titan's Lower Atmosphere and on
its Surface
PI: Peter Smith (Lunar and Planetary Laboratory)
Proposal: 5776
Title: Observations of the 1994 Spot on Saturn
PI: Reta Beebe (New Mexico State University)
Proposal: 5782
Title: Saturn Ring-Plane Crossing, May 1995
PI: Amanda Bosh (Lowell Observatory)
Proposal: 5824
Title: Occultation of GSC5249-01240 by Saturn: Atmospheric
and Ring Studies
PI: Amanda Bosh (Lowell Observatory)
Proposal: 5836
Title: Saturn Ring Plane Crossing Observations in August
and November 1995
PI: Philip Nicholson (Cornell University)
Proposal: 6030
Title: Clouds and Aerosols on Saturn and Uranus
PI: Martin Tomasko (Lunar and Planetary Lab)
Proposal: 6215
Title: Saturn's Aurora and Airglow
PI: John Trauger (Jet Propulsion Laboratory)
Proposal: 6216
Title: Saturn's Ring Atmosphere during Ring Plane Crossing
PI: John Trauger (Jet Propulsion Laboratory)
Proposal: 6295
Title: Imaging the Atmosphere of Titan and its Surface
PI: John Caldwell (York University)
Proposal: 6328
Title: Imaging and Spatial Scans of Saturn Near Ring-Plane
Crossing
PI: John Caldwell (York University)
In the specific case of the Titan proposals 5508 and 6295, some
images show Titan but not Saturn or its rings. These
particular images have not been archived in this data set;
however, they are obtainable from the HST Data Archive at:
http://archive.stsci.edu/
Files are distributed across this set of five CDROMs roughly
chronologically, as follows:
Volume Directory Proposal Dates # Images
RPX_0001 199410XX/U2IQXXXX 5219, Trauger 1994-10-09 7
199410XX/U2IZXXXX 5508, Smith 1994-10-05 6
1994-10-06 6
199412XX/U2KRXXXX 5776, Beebe 1994-12-01 9
199505XX/U2OOXXXX 6216, Trauger 1995-05-22 7
RPX_0002 199505XX/U2ONXXXX 5782, Bosh 1995-05-22 48
RPX_0003 199508XX/U2TFXXXX 5836, Nicholson 1995-08-09 8
1995-08-10 42
1995-08-11 4
RPX_0004 199508XX/U2OOXXXX 6216, Trauger 1995-08-10 4
199508XX/U2QEXXXX 6030, Tomasko 1995-08-06 8
199510XX/U2VIXXXX 6295, Caldwell 1995-10-01 8
1995-10-09 8
199510XX/U2WCXXXX 6215, Trauger 1995-10-15 4
1995-10-31 4
199511XX/U2QEXXXX 6030, Tomasko 1995-11-17 16
RPX_0005 199511XX/U2OOXXXX 6216, Trauger 1995-11-20 3
199511XX/U2TFXXXX 5836, Nicholson 1995-11-21 20
1995-11-27 8
199511XX/U2ZNXXXX 6328, Caldwell 1995-11-18 10
199511XX/U2ZYXXXX 5824, Bosh 1995-11-21 2
1995-11-22 4
Parameters
==========
WFPC2 observations record the image brightness of Saturn and or
its rings and moons in a particular filter for the specified
exposure time.
The PDS label for each file contains a broad variety of
additional parameters enabling the user to determine image
geometry and to convert pixel values to physically meaningful
quantities.
Processing
==========
The calibrated images have been passed through the Space
Telescope Science Institute's processing 'pipeline' which
includes: analog-to-digital conversion, bias level correction,
bias correction, dark current correction, and flat field
correction. For a detailed outline, see [BIRETTAETAL1993].
Data
====
The data provided here are images and tables in FITS format, as
provided by the Space Telescope Archive. For each data file, a
detached PDS label is provided containing additional
parameters.
Most users will prefer to focus on the fully calibrated images
found in the CALIMAGE subdirectories of these volumes. Such
files have been through the full HST processing pipeline and so
are relatively straightforward to interpret both geometrically
and photometrically. The detached PDS label files contain the
key parameters needed to perform this interpretation.
The other especially useful subdirectories are those entitled
BROWSE, which contain easy-to-display GIF files showing the
images at compressed scale and with the four fields of view
(PC1, WF2, WF3, WF4) mosaicked into a single image. These
files are especially useful when the user desires only a quick
look at what the images contain.
Additional files are as follows:
Subdirectory STScI file File contents
extension
CALMASK .c1f quality mask for calibrated image.
ENGDATA .x0f extracted engineering data.
ENGMASK .q1f quality mask for engineering data.
HEADER .shf standard header containing
observation parameters.
RAWIMAGE .d0f raw image.
RAWMASK .q0f data quality mask for raw image.
See Chapter 25 of the HST Data Handbook for more information
about these files.
Ancillary Data
==============
Additional geometry and calibration files are provided to
assist in the analysis and interpretation of the data.
On each volume, the CALIBRATION subdirectory contains filter
profiles for (most of) the filters used in this data set. It
also contains a model solar spectrum.
The first volume of this set contains a GEOMETRY subdirectory,
containing ephemeris files for Saturn and its satellites, plus
the Sun, Earth, and Moon. These files are provided in SPICE
format for a variety of platforms. For more information about
SPICE data and toolkits, consult the PDS Navigation and
Ancillary Information (NAIF) Node at:
http://pds.jpl.nasa.gov/naif.html
Coordinate System
=================
All geometric quantities appearing in the labels are in J2000
coordinates. In this coordinate frame, the z-axis points
northward along the Earth's J2000 rotation axis and the x-axis
points toward the First Point of Aries.
Media/Format
============
This data set is archived on compact disc (CDROM) media.
Organization and formats are according to PDS and ISO 9660
level 1 standards.
Files are in FITS format, with detached PDS labels. The FITS file
standard is described in 'Definition of the Flexible Image Transport
System (FITS) Standard', from the NASA/Science Office of Standards
and Technology. Specific information about STScI's usage of FITS
keywords is found in the HST Data Handbook.
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CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
The well-known problems of HST's mirrors and the corrections
for the WFPC2 are discussed in [BIRETTAETAL1996]. Filter
characteristics, calibration procedures and a description of
the methane filter are also included in this reference.
Review
======
This data set passed peer review on September 30, 1999. The
members of the peer review panel were Amanda Bosh, Richard French,
Lyle Huber, Stephen Larson, Claude Roddier, and Philip Nicholson.
Ron Joyner represented the PDS Central Node at JPL.
Data Coverage and Quality
=========================
Saturn was imaged continuously during the hours surrounding
Earth's crossings of the ring plane on May 22, 1995 and August
10, 1995. Saturn was too close to the Sun for observations on
February 11, 1996. Nearly-continuous imaging also occurred
during the ring 'sunset' on November 21, 1995. During these
periods of ring-targeted observing, images are of extremely high
quality.
Naturally, images intended for observations of Saturn and/or
Titan are not always exposed optimally for ring and ring-moon
science.
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