The High Resolution Imaging Channel of the SIMBIO-SYS instrument for the BepiColombo mission to Mercury.
Colangeli, Luigi ; Palumbo, Pasquale ; Marra, Gabriella ; ...Flamini, Enrico ; et al.
Jan - 2006

journal : Memorie della Società Astronomica Italiana Supplement

Volume : 9 ; Issue : 170
type: Article Journal

Abstract
The SIMBIO-SYS (Spectrometers and Imagers for Mercury Planetary Orbiter (MPO) Bepi- Colombo Integrated Observatory SYStem) instrument is a suite for imaging and spectroscopic investigation included in the scientific payload of the ESA BepiColombo mission to Mercury, planned at launch in 2013. SIMBIO-SYS is an international project led by Italy, with major contributions from France and Switzerland. The SIMBIO-SYS capabilities will allow an integrated investigation of the planet surface, providing information on the geology, topography and geo-chemical composition. The High Resolution Imaging Channel (HRIC) of SIMBIO-SYS, developed under ASI contract, has the main objective of characterising relevant Mercury surface features at very high spatial resolution (pixel scale of about 5 m at 400 km from planet surface) in the visible; this is a major challenge and improvement with respect to previous instruments observing Mercury. The high resolution images of selected regions will allow us to identify key surface features (e.g., craters, scarps, lava flows and plains) and to study their relation with internal processes, as well as the effect of external agents, such as meteor bombardment. In addition, HRIC images will be of paramount importance in support of experiments aiming to the identification of Mercury orbital parameters, such as the obliquity and the amplitude of the libration. Starting from the very stringent spatial resolution requirement, the optical design of the channel has been optimized in order to maximize the instrument performance, within mass and volume allocations. The HRIC optical configuration is catadioptric and is diffraction limited at 400 nm. It optimises radiometric flux and overall mechanical dimensions, guarantying a good balance of achieved optical performances and optimisation of resources (mainly, volume and mass). The corrected field of view will be covered by an innovative CMOS hybrid sensor of 2k x 2k pixels, with pixel size of 10 µm. The adopted configuration corrects and transmits well over the whole band of observation (400 - 900 nm). A panchromatic filter and three band-pass filters, to help in geo-mineralogical characterisation of local surface features, are foreseen. Operations have to be carefully planned to properly combine BepiColombo orbital characteristics with HRIC optical configuration in order to achieve the mail goals of the mission. For this purpose, a complete modelling chain including a radiometric model and an instrument simulation tool have been developed, capable to reproduce the expected image characteristics as a function of operative conditions

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