EnVision VenSAR Altimetry of Venus

The EnVision mission slated for launch in 2031, will revisit Venus decades after Magellan last made satellite measurements of Venus. In addition to hyper-spectral imagers (VenSpec Suite \cite{venspec}) for characterizing the Venus atmosphere, and ground penetrating radar (SRS \cite{srs}) for measuring subsurface structure, EnVision will characterize the surface Venus using VenSAR \cite{vensar}, a multi-mode S-band radar. VenSAR is designed for imaging Venus using Synthetic Aperture Radar (SAR) with repeat observations spread over several years to detect changes on the surface of Venus, characterizing Venus surface via polarimetric SAR and radiometry and for making high resolution topographic maps of Venus using Radar Altimetry and SAR Stereo. This article describes the VenSAR altimeter mode, its design, operation and expected performance.