Description of the Rhea SPC Shape Model and Assessment Products bundle V1.0 =========================================================================== Bundle Generation Date: 2025-08-22 Peer Review: 2025_Asteroid_Review Discipline node: Small Bodies Node =============================================================================== We provide the shape model, also known as a global Digital Terrain Model (DTM), of the Saturnian satellite Rhea, along with assessment data. This is the first Rhea model submitted to the PDS, and is generated using the Stereophotoclinometry (SPC) software suite. The shape model is provided in a variety of formats. To aid the data user, filenames end with a letter to designate the format. These letters are “i”, “c”, “g”, “p”, and “o”, respectively. "i" - ICQ - Implicitly Connected Quadrilateral format, one of the smallest data size formats. It is defined in icqmodel.asc of Gaskell (2020). "c" - ISIS - The native cube format for the United States Geological Survey (USGS) Integrated Software for Imagers and Spectrometers. "g" - GeoTiff format, an expanded version of TIFF images that maintains physical geometric information, which is especially useful by GIS programs like ArcGIS. “p" - Plate vector format, an older format used by the Planetary Science community. "o" - OBJ, a plate vector format, and an Object Vector format, created by Alias Wavefront but is currently one of the most common formats for 3D models. This format is the native format for the Small Body Mapping Tool (SBMT). We also provide quality assessment data for the shape model to include the best image resolution, number of images, best maplet resolution, and the sigma value. The quality data is presented in 1 degree bins using the USGS ISIS cube format. The assessment data show that the radius of the global DTM is everywhere good. Higher resolution regional models could be generated everywhere, even at the poles. Details about the products are given in document/productdescription.pdf, while the assessment and thumbnails of the assessment data are given in document/rheashapeassessment.pdf. The shape assessment PDF is particularly important. The SPC shape model is compared against an example Cassini image in document/rheavisualcmp.pdf to show compatibility with the limb profile. The model was constructed using the CASSINI Imaging Science Subsystem (ISS) Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) images. Images were used irrespective of the filter. Calibrated 32-bit images are used, and a correction for geometric distortion is used for all images. The image list for the global model, as well as the kernel list, are included as text documents. The shape model is provided in two resolution versions for the ICQ, PLT, and OBJ. One version has a higher resolution of 2.15 km Ground Sample Distance (GSD), and the other has a lower resolution with a 8.6 km GSD since many software programs cannot read the higher resolution version. The cubes and geoTiffs of the global model have a single version, that of a GSD of 2.15 km. Since the maplets that make up the shape model everywhere have a higher resolution than the global model, a good rule of thumb for the global uncertainty is to base it off the shape model GSD. The uncertainty is then one to two times the shape GSD. This gives 2.15 to 4.3 km uncertainty. Caveats to the data user ======================== None.