Data Set Information
DATA_SET_NAME WHT S API ISIS RAW AND CALIBRATED RING PLANE CROSSING V1.0
DATA_SET_ID WHT-S-API/ISIS-1/3-RPX-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This dataset contains images and spectra of the Saturn system taken at the William Herschel Telescope (WHT) using the Auxiliary Port Imager (API) and the Intermediate Dispersion Spectrograph and Imaging System (ISIS) in early August, 1995. This period precedes the actual August plane crossing by some ten days. The viewing geometry was such that Earth and the Sun were on opposite sides of the ring plane, and the ring opening angle as viewed from Earth was approximately 0.2 degrees. Every 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. The WHT observing program whose results are included in this data set is: Proposal: GR/K94546 Title: Unknown PI: Carl Murray (Queen Mary, University of London) Objectives : There were two primary objectives for this set of observations: 1. Observe the inner Saturnian system. a. Attempt to detect suspected but unconfirmed small satellites [GORDONETAL1995] b. Reacquire small inner satellites for astrometry, especially Prometheus and Atlas following the questions arising from the April 1995 HST observations [BOSH&RIVKIN1996]. c. Attempt to detect the mysterious new features detected in the April 1995 HST observations [BOSH&RIVKIN1996]. d. Monitor the atmosphere of Saturn for disturbances. This was included since the planet would be in the field of view for all of the inner system observations and with a suitable filter would not be saturated except in the longest exposure images. A narrow band methane filter centered at 8920 Angstroms with Full Width at Half Maximum of 50 Angstroms was used for all of the inner system observations. 2. Obtain spectral observations of the E ring to determine if the ring does have a strong bias in the blue end of the spectrum as indicated in observations made during the 1980 ring plane crossing [LARSONETAL1982]. Observation summary and conditions : The primary instrument for these observations was the Intermediate Dispersion Spectrograph and Imaging System (ISIS). This is a narrow slit instrument; consequently, absolute spectra would not be obtained. The program called for also obtaining ISIS spectra of Enceladus, known to be spectrally neutral, then by subtraction obtain a relative spectrum of the E ring. At the outset, the seeing was too marginal to allow useful observations with ISIS due to partial cloud cover and Sahara dust in the upper atmosphere. Consequently, on each night a set of API images were obtained of the E ring using different filters as insurance. Late on the second night the seeing improved to approximately 0.1 arcsec and a good spectra for both the E ring and Enceladus were obtained with ISIS. As a consequence, the insurance observations were never fully processed. They are included as raw data only. Parameters : 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 processed using IRAF. This includes: analog bias correction, dark current correction, flat field correction, and sky correction. Spectra wavelengths were registered with a copper-argon reference source and compared to known absorption lines in the spectra. Data : The data provided here are images in FITS format and also in ASCII tables. For each data file, a detached PDS label is provided containing additional parameters. Most users will prefer to focus on the fully calibrated images and reduced spectra found in the DATA/IMAGES/CALIMAGE/ and DATA/SPECTRA/EASYISIS/ subdirectories respectively. The other potentially useful subdirectory is entitled DATA/IMAGES/BROWSE/, which contains easy-to-display GIF files showing the calibrated images at reduced resolutions. These files are especially useful when the user desires only a quick look at what the images contain. Subdirectory file name File contents DATA/SPECTRA/RAWISIS/ FxxxxxxR.IMG raw 2D spectrographs DATA/SPECTRA/CALISIS/ FxxxxxxC.IMG calibrated 1D spectra DATA/SPECTRA/EASYISIS/ aaaaaa.TAB ASCII table reduced spectra DATA/SPECTRA/RAWAPI/ FxxxxxxR.IMG raw filter sequence images DATA/IMAGES/BROWSE/ FxxxxxxR.GIF reduced resolution images DATA/IMAGES/CALIMAGE/ FxxxxxxR.IMG calibrated images DATA/IMAGES/RAWIMAGE/ FxxxxxxR.ZIP raw images Ancillary Data : Additional calibration files are provided to assist in the analysis and interpretation of the data. The appropriate subdirectories under the CALIBRATION subdirectory contain bias, flat field, sky, and spectral standard files as well as filter profiles for most of the filters used in this data set. 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 3 standards.
DATA_SET_RELEASE_DATE 2004-02-29T00:00:00.000Z
START_TIME 1995-08-01T04:00:00.000Z
STOP_TIME 1995-08-03T06:30:00.000Z
MISSION_NAME SATURN RING PLANE CROSSING 1995
MISSION_START_DATE 1994-01-01T12:00:00.000Z
MISSION_STOP_DATE 1997-01-01T12:00:00.000Z
TARGET_NAME SATURN
S RINGS
ATLAS
CALYPSO
DIONE
ENCELADUS
EPIMETHEUS
HELENE
JANUS
MIMAS
PANDORA
PROMETHEUS
RHEA
TELESTO
TETHYS
TARGET_TYPE PLANET
RING
SATELLITE
INSTRUMENT_HOST_ID WHT
INSTRUMENT_NAME AUXILIARY PORT IMAGER
INTERMEDIATE DISPERSION SPECTROGRAPH AND IMAGING SYSTEM
INSTRUMENT_ID API
ISIS
INSTRUMENT_TYPE CAMERA
SPECTROGRAPH
NODE_NAME Planetary Rings
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : Marginal observing conditions for much of this data limit the amount of good information; see 'Data Coverage and Quality' below. ISIS spectra were calibrated using a Copper-Argon reference standard and known absorption features in the spectra. API CCD scale and orientation were obtained by fitting relative positions of the available satellites from the set {Enceladus, Tethys, Dione and Rhea} in each with predictions based on [HARPER&TAYLOR1993], and [HARPER&TAYLOR1994]. Review : This data set passed peer review on January, 30, 2004. The members of the peer review panel were James ('Gerbs') Bauer, Imke de Pater, Douglas Hamilton, and Steve Larson Ron Joyner and Steven Adams represented the PDS Central Node at JPL. Data Coverage and Quality : At the outset, the seeing was marginal, and entirely unsuitable for the use of ISIS, throughout the first night and well into the second night. Consequently, several filter series of the E Ring were obtained with the API as insurance. As a result of improved seeing late on the second night, ISIS spectra were obtained and as a consequence, the API filter sequences were not processed. However, the raw images are included. For approximately the last two hours of the second night, the seeing improved to approximately 0.1 arcsec. The best images of the inner system begin with image F161225X.IMG. During this period good spectra were obtained with ISIS for the E ring and Enceladus (to be used to obtain relative spectral information for the E ring). E ring spectra were obtained near the east ansa in a region which was free of satellites. The field of view of the API imaging system is sufficient to allow a single main ring image to extend beyond both ansae including the satellite orbits to beyond the orbit of Dione. All four of the classically known inner satellites were imaged, including a sequence showing the eclipse of Mimas by the rings. In addition, several of the small inner satellites, including Prometheus can be identified in several images. A few features can be detected moving with the mean motion of the F Ring, including at least one detection that has been identified as a prediscovery detection of 1995/S6. With the exception of the longest exposure images, main ring images contain some details of Saturn's upper atmosphere.
CITATION_DESCRIPTION Murray, C.D., S.M. Larson, D.H.P. Jones, M.K. Gordon, and O. Munoz, WHT Observations of the August 1995 Saturn Ring Plane Crossing, WHT-S-API/ISIS-1/3-RPX-V1.0, USA_NASA_PDS_RPX_0101, NASA Planetary Data System, 2004.
ABSTRACT_TEXT Unknown
PRODUCER_FULL_NAME MITCHELL K. GORDON
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