MERTIS - BepiColombo

 MERTIS flight model ready for delivery
zum Bild MERTIS flight model ready for delivery

MERTIS (MErcury Radiometer and Thermal infrared Imaging Spectrometer) is part of ESA’s BepiColombo Mercury Planetary Orbiter mission to the innermost planet of the Solar system. MERTIS is designed to identify rock-forming minerals, to map the surface composition, and to study the surface temperature variations with an uncooled microbolometer detector in the hot environment of Mercury. MERTIS is an advanced IR instrument combining a push-broom IR grating spectrometer (TIS) with a radiometer (TIR) sharing the same optics, instrument electronics and in-fight calibration components for a wavelength range of 7-14 and 7-40 µm, respectively.

First results of the ongoing MESSENGER project at Mercury have shown a more complex geology and higher variability of features than previously thought. The MESSENGER studies have demonstrated the need to gain global high-resolution mid-IR spectral and temperature data to achieve a better understanding of the planetary genesis. The MERTIS measurements will acquire this currently missing data set. MERTIS will provide a global mineralogical map of the surface of Mercury at a spatial resolution of 500m and a temperature map at a spatial resolution of 2000m. MERTIS will be able to measure the nightside temperatures down to 80K with an accuracy of 1K which will allow to derive thermophysical properties of the surface including texture and grain size.

 Final calibration verification of the MERTIS flight model at PEL
zum Bild Final calibration verification of the MERTIS flight model at PEL

The MERTIS instrument is developed in collaboration between the University of Münster and DLR with Kayser-Threde as industrial prime contractor. MERTIS represents a highly miniaturized modular concept of the sensor head, electronic units and power/calibration systems within a mass budget of only 3.0 kg and power consumption of less than 12 W nominal. The instrument uses an uncooled microbolometer, developed under ESA contract at LETI and ULIS in France. This is the first space-qualified microbolometer developed and built in European. It is based on the commercial detector with 160 x 120 pixels with a pixel size of 35 µm. Sharing the same optical path a pushbroom micro-radiometer is implemented by an in-plane separation arrangement.

All science operations and the scientific data processing of the MERTIS instrument will be performed at our institute. From here data will be distributed to the whole MERTIS science team. The PEL as reference laboratory will provide spectral measurements under vacuum and at high temperatures essential for the analysis of the MERTIS data. MERTIS will produce large amounts of data which require automatic classification techniques. We are currently developing an array of clustering techniques and filtering algorithms based on neural network approaches. These techniques are tested on MESSENGER data as part of our participation in the mission.

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