MERTIS seeing the Moon in the TIR: results from first BepiColombo

Kurzfassung

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is part of the ESA BepiColombo Mercury Planetary Orbiter (MPO) payload and consists of a push-broom IR-spectrometer (-TIS) and a radiometer (-TIR) [1]. MERTIS-TIS and -TIR make use of the same optics, electronics, and inflight calibration components [2, 3]. MERTIS-TIS operates at wavelengths of 7-14 µm, has 78 spectral channels, and a spectral resolution of λ/∆λ=78-156. The radiometer operates between 7 and 40 µm with 2 spectral channels. Depending on surface characteristics, MERTIS spectral resolution is adapted to optimize the S/R ratio. Thus, the instrument is capable of resolving weak spectral bands with less than 1% contrast. During the long cruise to Mercury, and before its arrival on December 5th 2025, BepiColombo will perform 9 flybys: among them, the Earth/Moon flyby on April 10 th 2020. Due to the flight configuration, not all the instruments onboard BepiColombo are able to operate during cruise and flybys. Among the instruments that can operate is MERTIS. The MERTIS imaging spectrometer will provide the first hyperspectral observation of the Moon in the thermal infrared (TIR) wavelength range from space. At the Planetary Spectroscopy Laboratory (PSL) of DLR in Berlin, a spectral library for lunar analog rocks in the TIR spectral range, measured under simulated Moon surface conditions, has been built to help the interpretation of MERTIS’ Moon spectra.