Mars Rover Colour Vision: Generating the True Colours of Mars

Mars rover colour vision typically employs multi-spectral imaging to generate natural-colour images that allow a planet to be viewed as if a human was present on the surface. As surface colour is dependent upon both surface reflectance/absorption properties and the surface illumination, getting the surface solar spectrum irradiance correct is vital for planetary colourimetry. Associated with a solar spectral power distribution (SPD) is its correlated colour temperature (CCT) which determines the reference white point for the colour image processing. If the CCT is wrong, the the white point will be wrong, and hence the colours will be wrong. New methods are being deveooped whereby a 'typical' Mars sol-light spectral distribution can be computed based upon the actual or desired CCT. Knowledge of the CCT allows the application of new chromatic adaptation transformations, whereby the martian surface can be viewed as if it had been illuminated by other terrestrial light sources as opposed to just Mars sol-light. The paper presents early results towards generating 'typical' Mars illuminants, and provides examples of CCt-based natural-colour image generation, and chromatic adaptation