In-situ Spectral Acquisition in NIR as Analog to Venus Emissivity Mapper (VEM)

Abstract

Little is known of Venus. A massive atmosphere obscures the surface, and extreme conditions prevent landers from gathering sufficient data. Although the atmosphere cannot be penetrated within the visible wavelength range, it has long been understood that a series of windows exists in the NIR, at a range of around 1µm, through which the surface emissivity can be observed. The VenSpec-M on board EnVision and the Venus Emissivity Mapper (VEM) on board VERITAS are two near future missions to Venus that will use this 1 µm spectral range to map the surface through emissivity of the night-side. In order to better understand the spectral data from these future missions, a VEM emulator (VEMulator 1.0) has been set up and brought to the island of Vulcano in the south of Italy to image volcanic materials as analogue to Venus’ surface. The data will be used to understand what calibration and analysis techniques will be needed to understand data collected from future emulators. The main goal is to characterize the spectra from the fresh and old volcanic rocks with different compositions, using a broad 1 µm spectral range. Following the data acquisition, spectra have been extracted from the VEMulator images and compared to spectra derived from laboratory spectroscopy (at PSL-DLR-Berlin). Flat field corrections were applied for calibration. Results for calibrated spectra of known objects have proven to be comparable, if not immediately recognizable. Several alteration minerals were detected using data from PSL and VEMulator, providing proof of concept. Future improvements to the VEMulator 2.0 will increase accuracy of measurements and results.