The Design of an Infrared Sensor for the Measurement of Martian Surface Temperature and Gas Concentration

Design considerations for a temperature sensor to be launched onboard the space mission MetNet precursor to Mars are presented. An IR multispectral sensor has been proposed to measure Martian surface temperature to an accuracy of plusmn1 K without knowing ground emissivity. Two methods for temperature retrieval have been assessed, both relying on comparative measurements at two wavelengths and/or two temperatures. Spectral calculations of surface emission and atmospheric absorption-emission have been made with a simple Martian atmosphere model, and signal to noise ratios have been estimated at transparent wavelengths for several temperatures. Temperature accuracy has been derived for the two methods, showing that bi-color pyrometry has in principle the ability to provide the desired temperature accuracy for reasonable values of sensor detectivity, field of view and spectral filter width, for T > 200 K. This sensor can be applied also to estimate CO₂ concentrations in the Martian atmosphere, by comparing signals measured at CO₂ absorption and transparent bands.