Multi-band processing of observations of the polar regions of Mars with the Omega imaging spectrometer on board Mars Express

The Omega imaging spectrometer on-board the Mars Express ESA mission has observed the surface of Mars during more than 3 Martian years since orbit insertion in January 2004. The spectral cubes (352 spectels from 0.36 μm to 5.1 μm, IFOV from 0.3 to 5 km, swath width 16 pixels to 128 pixels) provide unique information on martian polar processes as there are very strong signatures of CO₂ ice and H₂O ice in the near IR spectral range. These two ices can be discriminated with multi-band processing, which can also identify the contribution of aerosol scattering when combined with a Monte-Carlo radiation transfer model. This made it possible to investigate the advance and retreat of seasonal caps, the composition of perennial caps and the presence of ices in aerosols. Work in progress with OMEGA focuses on two main issues: inter-annual variability (mainly observed for time-varying phenomena at high latitudes) and modeling of the impact of aerosols on observed spectra so as to retrieve the spectral characteristics of the surface while obtaining information on the composition, grain size and altitude distribution of aerosols. A 3-D model dedicated for observations at very high incidences has recently been developed and will be applied to high latitude observations.