Data Set Overview : This dataset contains astrometric data for fourteen Saturn satellites. The data were obtained using the HST/WFPC2 over the period 1996-2005. The volume contains only derived products. PI: Richard G. French (Wellesley College)  Objectives : The observations from which these results were derived were part of a long term investigation of Saturn's rings prior to Cassini's arrival in 2004. The primary intent of this specific portion of the investigation was to refine orbital information for Prometheus and Pandora. Observations made during the 1995-1996 Saturn Ring Plane Crossing led to the unexpected finding that the positions of both satellites varied significantly from the predictions based on the Voyager observations (BOSH&RIVKIN1996, NICHOLSONETAL1996, MCGHEEETAL2001, SYNNOTTETAL1983). Sufficient observations to produce astrometrically meaningful data for nine other satellites were obtained incidentally in the Prometheus-Pandora observing campaign. The data for those satellites is also included in this data set.  Observation summary and conditions : For this investigation the primary new observations are from the ongoing HST WFPC2 campaign to observe the main rings of Saturn over the full range of ring tilt and phase angles visible from the Earth (1996-2005). These observations were made near opposition and quadrature. The overall quality of the images used is excellent.  Processing :  See FRENCHETAL2006.  Data : The data provided here are in ASCII tables. For each data file, a detached PDS label is provided containing additional information.  Most users will prefer to focus on the PDS compliant data files in the DATA/EASYDATA/ subdirectory. These files and their labels contain all of the information in the original files provided by R. French. The original files are included for completeness and can be found in the DATA/SORCDATA/ subdirectory.  In the all of the filenames we have incorporated a portion of the original filenames. The suffix 'REV8' refers to an internal revision number used by the primary investigator. Also, In the SORCDATA subdirectory, the files also have another suffix, 'GO', this refers to global offsets applied to the raw data. Details of this can be found in FRENCHETAL2006.  The satellites for which data are included in this volume are: Calpso, Dione, Enceladus, Epimetheus, Helene, Hyperion, Janus, Mimas, Pandora, Prometheus, Rhea, Telesto, Tethys, and Titan.  Satellite positions have been determined and are recorded in the individual table files by satellite. The data include the WFPC2 image name, the midpoint UTC time of the observation, the arcsec offsets from the center of the planet (RA*Cos(Dec) and DEC), with their corresponding formal uncertainties. Details of the observations and reduction techniques may be found in FRENCHETAL2003.  Ancillary Data : Calibration data is not provided. SPICE SPK files containing ephemeris information for the HST during the period covered by this data set are included in the SPICE/ directory.  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. Although the satellite ephemeridies provided to the team for use in their calculations were in the International Celestial Reference System (ICRF), all calculations treated them as if they were in J2000.  Furthermore, all of the calculations are geocentric rather than 'HST-centric'. During peer review, Dr N. Cooper noted the difference is insignificant at the accuracy of this data. He performed multiple orbit fits to the data for each satellite. The resulting elements were effectivly the same whether using HST or the center of the Earth as the observation point. The differences in the derived orbital elements were much smaller than the associated errors.

Confidence Level Overview : High.  Review :These data completed peer review in June 2008. Members of thepeer review panel were: Nick Cooper, Mike Evans, Richard French,Robert Jacobson, Ron Joyner, Colleen McGhee.