Thermal infrared imaging of Mercury - MERTIS - a new remote sensing technology

Abstract

MERTIS (MERcury Thermal infrared Imaging Spectrometer) is an advanced infrared remote sensing instrument that is part of the ESA mission BepiColombo to the planet Mercury. The scientific goals of MERTIS science are surface composition analyses, identification of rock-forming minerals, mapping of the surface mineralogy, and studies of surface temperature variations. MERTIS combines a push-broom IR grating spectrometer (TIS) with a radiometer (TIR), which operate in the wavelength region of 7-14 μm (TIS) and 7-40 μm (TIR), respectively. The instrument represents a modular concept of the sensor head, electronic units and power/calibration systems. The integrated instrument approach allows the subsystems TIS and TIR to share the same optics, instrument electronics and in-fight calibration components. The instrument is designed to achieve a signal-to-noise ratio above 100 in the 7-14 μm wavelength range with a spectral channel width of 90 nm. The TIS optical design combines a three mirror anastigmat (TMA) with a modified Offner spectrometer. The spatial resolution will be about 500 m globally and better than 500 m for 5-10% of the Mercury's surface. With an uncooled microbolometer detector, the instrument can be operated in the hot environment of Mercury without the need for a cryogenic cooling system. We are reporting on the measurement requirements, the status of the instrument development, and ongoing qualification efforts.