A novel optical design for the stereo channel of the imaging system Simbiosys for the BepiColombo ESA mission

In this paper the design of a novel catadioptric optical solution for the Stereo Channel (STC) of the imaging system SIMBIOSYS for the BepiColombo ESA mission to Mercury is presented. The main scientific objective is the 3D global mapping of the entire surface of Mercury with a scale factor of 50 m per pixel at periherm in five different spectral bands. The system consists of two sub-channels looking at ±20° from nadir. They share the detector and all the optical components with the exception of the first element, a rhomboid prism. The field of view of each channel is 5.3° × 4.5° and the scale factor is 23 arcsec/pixel. The system guarantees an aberration balancing over all the field of view and wavelength range with optimal optical performance. For stray-light suppression, an efficient baffling system able to well decouple the optical paths of the two subchannels has been designed.