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The Ma_MISS miniaturized spectrometer is integrated within the Drilling System of the ExoMars Rosalind Franklin Rover for Mars exploration. Here we focus on the on ground calibration campaign to obtain radiometric and linearity calibrations of the Ma_MISS instrument, while the first paper dealt with the spectral calibration [De Angelis et al., Rev. Sci. Instrum. 93, 123704 (2022)]. The experimental setup used to carry out radiometric calibration is described, as are the methods used for data processing and key parameter retrieval. In particular, the Spectrometer Transfer Function (Responsivity), Signal-to-Noise Ratio, and detector linearity are determined. In a third paper [De Sanctis et al., Planet. Sci. J. 3, 142 (2022)], validation of the Ma_MISS calibration results through spectral measurements performed on rock and synthetic targets during the radiometric calibration campaign is described., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

The STereo imaging Channel (STC) is the first push-frame stereo camera on board an European Space Agency (ESA) satellite, i.e., the ESA-Japan Aerospace eXploration Agency mission BepiColombo. It was launched in October 2018, and it will reach its target, Mercury, in 2025. The STC main aim is to provide the global three-dimensional reconstruction of the Mercury surface. STC, the stereo channel of spectrometer and imagers for Mercury Planetary Orbiter BepiColombo-Integrated Observatory System, is based on an original optical design that incorporates the advantages of a compact unique detector instrument and the convenience of a double direction acquisition system. In fact, STC operates in a push-frame imaging mode and its two optical sub-channels will converge the incoming light on a single focal plane assembly allowing to minimize mass and volume. The focal plane of the instrument is housing six different filters: two panchromatic filters in the range 600-800 nm and four broadband filters with central wavelengths in the range 420-920 nm. In this paper, the geometrical calibration of the instrument, including the optical setups used, will be described. The methods used to derive the focal lengths, the boresights, and the reference systems of the different filter models are presented, and the related distortion results are discussed. The STC off-axis configuration forced to develop a distortion map model based on the RFM (rational function model). In contrast to other existing models, which allow linear estimates, the RFM is not referred to specific lens geometry, but it is sufficiently general to model a variety of distortion types, as it will be demonstrated in this particular case.

Before integration aboard European Space Agency BepiColombo mission to Mercury, the visible and near infrared hyperspectral imager underwent an intensive calibration campaign. We report in Paper I about the radiometric and linearity responses of the instrument including the optical setups used to perform them. Paper II [F. Altieri et al., Rev. Sci. Instrum. 88, 094503 (2017)] will describe complementary spectral response calibration. The responsivity is used to calculate the expected instrumental signal-to-noise ratio for typical observation scenarios of the BepiColombo mission around Mercury. A description is provided of the internal calibration unit that will be used to verify the relative response during the instrument's lifetime. The instrumental spatial response functions as measured along and across the spectrometer's slit direction were determined by means of spatial scans performed with illuminated test slits placed at the focus of a collimator. The dedicated optical setup used for these measurements is described together with the methods used to derive the instrumental spatial responses at different positions within the 3.5 ° field of view and at different wavelengths in the 0.4-2.0 μm spectral range. Finally, instrument imaging capabilities and Modulated Transfer Function are tested by using a standard mask as a target.

The Visible and near Infrared Hyperspectral Imager (VIHI) is the VIS-IR spectrometer with imaging capabilities aboard the ESA BepiColombo mission to Mercury. In this second paper, we report the instrument spectral characterization derived by the calibration campaign carried out before spacecraft integration. Complementary measurements concerning radiometric and linearity responses, as well as geometric performances, are described in Paper I [G. Filacchione et al., Rev. Sci. Instrum. 88, 094502 (2017)]. We have verified the VIHI spectral range, spectral dispersion, spectral response function, and spectral uniformity along the whole slit. Instrumental defects and optical aberrations due to smiling and keystone effects have been evaluated, and they are lower than the design requirement (<1/3 pixel). The instrumental response is uniform along the whole slit, while spectral dispersion is well represented by a second order curve, rather than to be constant along the spectral dimension.

The typically dark surface of the dwarf planet Ceres is punctuated by areas of much higher albedo, most prominently in the Occator crater. These small bright areas have been tentatively interpreted as containing a large amount of hydrated magnesium sulfate, in contrast to the average surface, which is a mixture of low-albedo materials and magnesium phyllosilicates, ammoniated phyllosilicates and carbonates. Here we report high spatial and spectral resolution near-infrared observations of the bright areas in the Occator crater on Ceres. Spectra of these bright areas are consistent with a large amount of sodium carbonate, constituting the most concentrated known extraterrestrial occurrence of carbonate on kilometre-wide scales in the Solar System. The carbonates are mixed with a dark component and small amounts of phyllosilicates, as well as ammonium carbonate or ammonium chloride. Some of these compounds have also been detected in the plume of Saturn’s sixth-largest moon Enceladus. The compounds are endogenous and we propose that they are the solid residue of crystallization of brines and entrained altered solids that reached the surface from below. The heat source may have been transient (triggered by impact heating). Alternatively, internal temperatures may be above the eutectic temperature of subsurface brines, in which case fluids may exist at depth on Ceres today.

The SPectral IMager (SPIM) facility is a laboratory visible infrared spectrometer developed to support space borne observations of rocky bodies of the solar system. Currently, this laboratory setup is used to support the DAWN mission, which is in its journey towards the asteroid 1-Ceres, and to support the 2018 Exo-Mars mission in the spectral investigation of the Martian subsurface. The main part of this setup is an imaging spectrometer that is a spare of the DAWN visible infrared spectrometer. The spectrometer has been assembled and calibrated at Selex ES and then installed in the facility developed at the INAF-IAPS laboratory in Rome. The goal of SPIM is to collect data to build spectral libraries for the interpretation of the space borne and in situ hyperspectral measurements of planetary materials. Given its very high spatial resolution combined with the imaging capability, this instrument can also help in the detailed study of minerals and rocks. In this paper, the instrument setup is first described, and then a series of test measurements, aimed to the characterization of the main subsystems, are reported. In particular, laboratory tests have been performed concerning (i) the radiation sources, (ii) the reference targets, and (iii) linearity of detector response; the instrumental imaging artifacts have also been investigated.