VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy): A Discovery Mission

Deep understanding of planetary habitability requires identifying key factors that govern the surface environment over time. Venus is the ultimate control case for understanding how Earth developed and maintained conditions suited to life. Venus very likely had elements essential to habitability such as past surface water and a dynamo. Tectonism and volcanism, which create chemical disequilibrium, very likely persist today. What caused Earth and Venus to diverge down different evolutionary paths? VERITAS would create foundational, co-registered data sets of high-resolution topography, imaging, spectroscopy, and gravity, on par with those available for Mercury, Mars, and the Moon. VERITAS would answer outstanding fundamental questions about the evolution of Earth's twin. The VERITAS payload consists of the Venus Interferometric Synthetic Aperture Radar (VISAR) and the Venus Emissivity Mapper (VEM), plus a gravity science investigation. VISAR is an X-band radar that provides: 1) a global digital elevation model (DEM) with 250-m postings and 6-m height accuracy, 2) Synthetic aperture radar (SAR) imaging at 30-m horizontal resolution globally, 3) SAR imaging at 15-m resolution for $> \boldsymbol{25\%}$ of the surface, and 4) surface deformation from repeat pass interferometry (RPI) with 2-cm vertical precision for $> \boldsymbol{12} \boldsymbol{(\sim 200\ \mathrm{x}\ 200\ \text{km})}$ targeted areas. VEM covers $\boldsymbol{ > 70\%}$ of the surface in six near-infrared (NIR) bands sensitive to iron composition located within five atmospheric windows, plus eight atmospheric bands for calibration and water vapor measurements. VEM would provide near-global maps of mafic to felsic rock type and will search for active and recent volcanism. VERITAS would use two-way Ka-band uplink and downlink from a low circular orbit $\boldsymbol{(< 250\ \text{km})}$ to create a global gravity field with 3-mGal accuracy of 155-km resolution (degree and order 123). An onboard technology demonstration, the Deep Space Atomic Clock (DSAC-2), may support radio science and navigation with one-way tracking. VERITAS data would enable estimation of elastic thickness (a proxy for thermal gradient) and density differences due to subsurface structures, as well as constraining interior structure, including core size and state. Lockheed Martin builds the spacecraft. VISAR is built by JPL, with the Italian Space Agency (ASI) providing the low power electronics. ASI also provides transponders and a high gain antenna for the telecom system. CNES provides the Ka-band traveling wave tube amplifiers (TWTA). The German Space Agency (DLR) provides VEM and contributes algorithms for VISAR ground and onboard data processing.