The Venus Emissivity Mapper (VEM) and the VenSpec-M on the NASA VERITAS and ESA EnVision missions, respectively, are multi-spectral imaging systems designed specifically for mapping the surface of Venus using near-infrared atmospheric windows around 1 μm. VEM/VenSpec- M will provide the first global map of rock types on the surface of Venus as well as constant monitoring for volcanic activity at global (VERITAS) and regional/local (EnVision) scales. The VEM/VenSpec- M verification plan ensures accurate performance and science return of the instrument and includes on-ground and in-flight instrument calibrations as well as supporting laboratory measurements for calibration and scientific data analysis. Pre-flight calibrations encompass geometric, spectral, and radiometric calibrations based on the MERTIS (on BepiColombo) calibration campaign and pipeline. Laboratory work involves the creation of spectral libraries of increasing complexity by measuring the emissivity of Venus analogs under Venus surface conditions. These data will distinguish between basalt and felsic rock types on the Venus surface and may enable the identification of intermediate compositions based on iron content. Data analysis uses machine learning models for classification between basalt and felsic rocks and regression to predict FeO content using laboratory calibration data. The data verification plan outlined here not only provides fundamental data needed for VEM/VenSpec-M, but can also be adapted to create data products suitable for calibration of the VenDi (Venus Descent Imager) instrument on the DAVINCI mission. Such use of an integrated calibration plan will benefit all three missions and produce coordinated results that can be directly compared.
Recently selected Venus missions, such as NASA's VERITAS, ESA's EnVision, and DAVINCI, are all equipped with instruments that focus on the 1 μm region in their payloads. Specifically, VERITAS and EnVision utilize the Venus Emissivity Mapper (VEM) as a multi-spectral imaging system. VEM is designed to provide global mapping of Venus's surface in all available spectral windows. Meanwhile, DAVINCI has a descent imager that obtains images of the surface around 1 μm. To support these missions, the Planetary Spectroscopy Laboratory (PSL) at DLR has a Venus spectroscopy setup consisting of a Bruker VERTEX 80V FTIR spectrometers with an attached vacuum chamber equipped with an induction heating system. PSL can measure emissivity spectra of Venus analogues at temperatures up to 1000K in the spectral range from 0.8 to 1.2 μm. Additionally, PSL has two hemispherical reflectance units available that can be mounted in the internal chamber of the Bruker VERTEX 80V spectrometer. PSL has already measured the emissivity of over 300 rock samples at Venus surface temperatures for calibration and verification efforts for VEM on VERITAS and the VenSpec-M channel on the EnVision mission. Hemispherical reflectance measurements are also taken for each sample. These data will be used for the basic and enhanced calibration datasets for the missions as well as all other Venus missions carrying similar instrumentation. Coordination and cross-calibration of the missions' instruments are crucial. Team members from VERITAS, EnVision, and DAVINCI are collaborating to establish a good cross-calibration between the missions. The data obtained by these missions will provide unique insights into the coupled surface-atmosphere system of Venus.
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