Venus Emissivity Mapper (VEM): Instrument status and detector qualification for EnVision and VERITAS

Abstract

We present the Venus Emissivity Mapper (VEM) onboard NASA's Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy (VERITAS) and ESA's (EnVision) Venus orbiter missions. The VEM instrument (on EnVision called VenSpec-M), is a multispectral imager for mapping of the Venus surface and its lower atmosphere. This is realized by observation through narrow-band atmospheric windows present in the near-infrared spectral region around 1 micrometer. For the first time, VEM will provide a global Venus coverage of >70% with a high signal-to-noise ratio on the order of 100 to detect thermal emissions like volcanic activity, surface rock composition, water abundance and cloud formation. Since VEM for VERITAS and VenSpec-M for EnVision are being developed almost simultaneously, the instrument development approach can be made very efficient. By tailoring the science level, interface and environmental requirements of both missions to a joint requirements baseline, a single instrument design can be established. Our presentation will focus on the current status of the VEM design and development, with a particular emphasis on detector qualification. Following the ion qualification test at the Radiation Effects Facility in Finland (RADEF), where heavy-ions were used to evaluate Single Event Effects (SEE) performance, we conducted a comprehensive proton irradiation test campaign at Helmholtz-Zentrum Berlin (HZB). This campaign included assessments for Total Ionizing Dose (TID) and Displacement Damage Dose (DDD) to quantify radiation-induced noise and proton-induced SEE susceptibility. Our imaging sensor demonstrated robust performance under these challenging conditions. We will also detail the instrument's software architecture and on-board data processing. Notably, we will discuss how a single on-board software can efficiently serve two distinct missions. The instrument software comprises a Boot Software (BSW) and application Software (ASW). The BSW's primary responsibility is to load and initiate the ASW from local Non-Volatile Memory (NVM). The Field-Programmable Gate Array (FPGA) executes nearly the entire science data processing, including Time-Delay Integration (TDI) and pixel binning to enhance the Signal-to-Noise Ratio (SNR). Due to the initial eccentric Venus orbits, regular on-board processing parameter reconfiguration is necessary to uphold the defined science performance. Once the final nearly circular orbits are achieved, constant binning will be possible, simplifying operations. The VEM/VenSpec-M project is transitioning into its detailed design phase. The in-strument preliminary design reviews (PDR) were held in 2025 for VERITAS and EnVision. Two flight models (FMs) are currently scheduled for delivery to the VERITAS S/C and one FM to the EnVision S/C. First VEM/VenSpec-M data obtained from Venus orbit is expected after launch of the two missions currently scheduled in 2031.