The ExoMars-Like Field Trials (ExoFiT): PanCam Emulator Multispectral Observations

Introduction: The search for life and habitable environments dominates the mission profile of many of the upcoming martian surface missions, including ExoMars2020 [1]. ExoFiT is the latest installment of martian surface simulation missions designed to test the response of the ExoMars Instrument suite in an analogue Mars location. This field trial aims to highlight the rover instrument capabilities, building upon the previous work of the MURFI trials, further information of which can be found here [2]. ExoMars Context instruments. The Context Instrument suite on the ExoMars 2020 rover will provide insight into the martian landscape, allowing for the selection of the most interesting geological features for further investigation and possible sampling. The Panoramic, wide angle, stereo imaging system (PanCam) [3] will take multispectral images in 12 narrowband channels in the visible to near-infrared range (from 440 nm to 1000 nm) [4], and will be imperative in understanding the geology of the landing site, as well as the mission planning and target site acquisition. The rover will also be equipped with the High Resolution Camera (HRC) to provide submillimetre textural information. Within the field of view of PanCam and HRC, the Infrared spectrometer for ExoMars (ISEM) takes point measurements of spectra in the range 1150 nm to 3300 nm [5]. The PanCam spectral range provides wavelength coverage of the identification features of Hematite and various ferrous minerals [3]), while the ISEM spectral range is more targeted for hydrous mineral signatures [5]. ExoSpec: To utilize the PanCam observations to best inform mission operations, the PanCam data must be analysed within the tactical planning time frame for inclusion in mission plans on subsequent sols. An ENVI extension has been developed to enable time effective analysis of ExoMars multispectral data, details of which can be found here [6]. The ExoSpec software first applies both flat field and radiometric corrections, followed by environment colour correction using an in situ image of the PanCam calibration target, located on the rover body. The reflectance values from the in situ image of the calibration target and previous lab measured values, are used to determine illumination coefficients to transform between a radiometrically corrected image and R* reflectance [7] images for analysis. Furthermore, ExoSpec contains multiple spectral parameters to aid in efficient analysis of PanCam images, with particular emphasis on Astrobiologically relevant features. EXOFIT Trial: The ExoFiT program consists of two field trials, the first of which was based in southern Spain in September 2018. The first trial consisted of a field team and rover platform with emulator instruments, including AUPE, the PanCam emulator used here. AUPE contains a similar 12 filter set to PanCam, within a few nm of PanCam’s central filter wavelengths [6]. The operations team, based in the Rover Control Centre (RCC) near Oxford in the UK, were given no location information except the data returned by instrumentation to guide the mission progress. This process provides insight into the data returned by PanCam and how best to utilise data within the strict time limit of the tactical planning phase, and best practices for meeting longer-term science goals. This first trial lasted for two weeks, with inclement weather at the field site limiting the mission to ~10 sols. Where possible, two sol missions were operated within one day to recover time lost due to inclement weather. Despite the compressed nature of the field trial, the overall goal was to follow the Reference Surface Mission (RSM) for ExoMars 2020 as closely as possible, including obtaining a deep drill sample.