Improved determination of Europa's long-wavelength topography using
stellar occultations
Abstract
Europa Clipper will arrive at Jupiter at the end of this decade and will
explore Europa through a series of flybys. One of its many goals is to
characterize Europa’s topography and global shape using the EIS and
REASON instruments. In addition, Europa Clipper’s UV Spectrograph will
observe stars pass behind (be occulted by) Europa. The spectrograph has
sufficiently precise timing, corresponding to a topographic precision of
order meters, that these occultations can also serve as altimetric
measurements. Because of gaps in the REASON radar altimeter coverage
imposed by the flyby geometries, the addition of ~100
occultations results in a substantial improvement in the recovery of
Europa’s long-wavelength shape. Typically five extra spherical harmonic
degrees of topography can be recovered by combining occultations with
radar altimetry.