MERTIS: from laboratory to Mercury

Abstract

MERTIS (MERcury Thermal infrared Imaging Spectrometer) is an advanced infrared remote sensing instrument that is part of the ESA mission BepiColombo to planet Mercury. The enabling technology that allows sending the first spectrometer for the thermal infrared spectral range to Mercury is an uncooled microbolometer. With this detector the instrument can be operated in the hot environment of Mercury without the need for a cryogenic cooling system. The challenge is the characterization and calibration of the instrument. We are reporting on the ongoing calibration efforts including laboratory measurements of analogue materials, end-to-end simulations and a detailed characterization of all components and discuss each of the three elements. The measurement of planetary analogue materials in grain sizes <25 μm and at temperatures up to 500°C relevant for Mercury's surface provide a realistic input signal for the end-to-end simulation. A radiometric and a spectroscopic breadboard model of MERTIS are used to derive all necessary parameters of the instrument, for example the spectral resolution or the wavelength registration on the detector. This parameters support setting up the end-to-end simulation which can then process the spectra of the planetary analog materials as input signal to create a realistic representation of the MERTIS output signal.