Abstract DGP2026-53

A Laboratory Imaging Emulator for the MERTIS Instrument in preparation for BepiColombo Mission: MIMIC

Akin Domac (1), Solmaz Adeli (1), Jörn Helbert (1,2), Christian Althaus (1), Alessandro Maturilli (1), Mario D'Amore (1), Oceane Barraud (1), Stephen Garland (1), Jörg Knollenberg (1), Ingo Walter (1), Nimisha Verma (1), Aurelie Van den Neucker (1), Giulia Alemanno (1), Andreas Lorek (1), Christopher Hamann (3), Kai Wünnemann (3), Harald Hiesinger (4)

(1) Institute of Space Research, DLR, Rutherford Str. 2, 12489 Berlin, Germany (2) European Space Research and Technology Centre, ESA, Keplerlaan 1, 2200 Noordwijk, The Netherlands (3) Leibniz Institute for Evolution and Biodiversity Science, Museum für Naturkunde, Invalidenstraße 43, 10115 Berlin, Germany (4) Institut für Planetologie (IfP), Universität Münster, Wilhelm-Klemm Str. 10, 48149 Münster, Germany

The MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument aboard the ESA–JAXA BepiColombo mission is designed to characterize Mercury’s surface mineralogy using thermal infrared spectroscopy in the 7-14 µm range [1,2]. During BepiColombo’s fifth Mercury flyby on 1 December 2024, MERTIS acquired the first spatially resolved mid-infrared spectra of Mercury’s surface, collecting more than 1.4 million spectra at spatial resolutions of approximately 26–30 km per pixel [3,4]. These observations revealed spectral variations associated with impact craters, bright and dark deposits, and other geological features, providing an important preview of the global dataset that will be obtained after Mercury orbit insertion in late 2026.

However, interpreting thermal infrared spectra of Mercury is challenging due to the planet’s extreme surface temperatures (~100–700 K) and strong thermal gradients, which produce non-isothermal conditions within individual MERTIS pixels. These conditions obscure mineralogical features by blending them with multiple temperature-dependent Planck radiation, making accurate determination of the emissivity a central challenge [1,5,6]. In addition, thermal infrared spectral features are influenced by physical surface properties such as grain size, porosity and surface roughness, further increasing interpretation uncertainties [7,8,9]. Robust analysis of the upcoming global MERTIS dataset therefore requires laboratory reference measurements under comparable conditions.

To support ongoing laboratory studies, we developed the MERTIS Imaging Model for Instrument Characterization (MIMIC), a dedicated laboratory emulator that reproduces the imaging geometry and spectral behavior of MERTIS. MIMIC is designed as a complementary approach to established bulk emissivity measurements acquired with Fourier-transform infrared (FTIR) spectroscopy, extending these methods by enabling spatially resolved thermal infrared imaging under Mercury-like thermal conditions at DLR’s Planetary Spectroscopy Laboratory (PSL). Through a mid-infrared transparent window mounted on a high-temperature, evacuated emissivity chamber, MIMIC produces imaging data that are comparable to MERTIS observations. This capability allows systematic investigation of how surface physical properties, such as grain size, grain shape (angularity and sphericity), porosity, and surface roughness, affect thermal emission at the pixel scale. By bridging laboratory spectroscopy with orbital observations, MIMIC offers a unique platform to improve the interpretation of MERTIS data and our understanding of mid-IR emission processes on airless planetary bodies.

[1] Hiesinger, H., et al., 2010, Planetary and Space Science [2] Helbert, J., et al., 2013, SPIE [3] Hiesinger, H., et al., 2025, LPSC [4] Adeli, S., et al., 2025, EPSC-DPS [5] Wohlfarth, K., et al., 2023, Astronomy & Astrophysics [6] Tenthoff, M., et al., 2025, EPSC-DPS [7] Maturilli, A., et al., 2006, Planetary and Space Science [8] Morlok, A., et al., 2016, Icarus [9] Martin, A.C., et al., 2025, JGR Planets