Accomodamento e prestazioni del payload ottico di bepicolombo, simbiosys, in relazione ai suoi requisiti scientifici

BepiColombo space mission (planned by European Space Agency in co-operation with Japanese Space Agency JAXA, launch scheduled for 2012), is intended for the study of planet Mercury, with two different spacecrafts: MPO (Mercury Planetary Orbiter) and MMO (Mercury Magnetospheric Orbiter). In order to analyze the geological and mineralogical characteristics of the Mercury surface and the exosphere, MPO module will have on board, among other instruments, SIMBIO-SYS (Spectrometers and Imagers for MPO BepiColombo – Integrated Observatory SYStem), an integrated package which has three different optical channels: - HRIC (High Resolution Imaging Channel), a high resolution camera operating in 400 – 900 nm spectral range (visible), - STC (Low Resolution Colour Imaging and Stereo Channel), a camera with stereoscopic and colour imaging capability, - VIHI (Visible and near-Infrared Hyperspectral Imager), a spectrometer in visible and near infrared spectral range. With the Monte Carlo ray tracing software Opticad, several simulations have been performed to evaluate the parameters influence on the design of a baffle: angle of incidence of the source, diameter of the aperture, number of vanes, thickness. Both a cylindrical baffle with plain vanes and a Stavroudis configuration has been considered. The results show that a reflecting Stavroudis baffle could be better than a plain vanes absorbing baffle for its natural rejection of rays (for construction this type of baffle traps very little rays). Also a thermal analysis has been performed, in order to complete the baffle evaluation: using the ESARAD software packet a model of the system under analysis was defined and then introduced in a simplified temperature distribution which approximately reproduces the thermal condition MPO payload will be immersed in.