Mars surface science results from the Emirates eXploration Imager (EXI)

The Emirates eXploration Imager (EXI) instrument onboard the Emirates Mars Mission (EMM) has a field of view (FOV) that is capable of capturing the full martian disk at periapsis. EXI has 6 band passes centered on 220, 260, 320, 437, 546, and 635 nm using two telescopes (ultraviolet, UV and visible, VIS) with separate optics and detectors. During the primary science mission full-disk images are acquired with a resolution between 2-4 km per pixel depending on orbit location (periapsis vs. apoapsis). Given the orbit of the EMM spacecraft, EXI is able to provide diurnal sampling over most of the planet on the scale of 10 days, which allows for the characterization of atmospheric constituents such as water ice clouds, ozone, and when present, monitoring of dust storms, on diurnal and seasonal timescales. Assessing the energy budget of the lower atmosphere is a science goal of EXI and EMM. It is critical to understand the contribution from the surface and as such, characterize its thermophysical properties (albedo and thermal inertia). Complimentary observations from EXI and the Emirates Mars Infrared Spectrometer (EMIRS) provide such capabilities. The work presented here includes initial results of EXI surface reflectance of 635 and 320 nm images spanning from orbit capture to early science phase. During orbit capture, the EMM spacecraft was much lower in altitude over several passes and EXI was able to acquire higher spatial resolution images. All images taken once the science orbit was achieved were of the full disk. In addition to providing new perspectives of the geology of Mars, the low altitude images help constrain the full disk albedo because they can be compared to previous datasets, such as the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) albedo, over similar observing conditions. Furthermore, we present initial EXI observations of contrast reversals. These are UV bright regions that typically correspond to low albedo features such as Syrtis Major, Acidalia Planitia, and Margaritifer Terra. These features have also been called ultraviolet reversal and were previously identified using Viking and Hubble Space Telescope observations.