MERTIS/BEPI COLOMBO Pointing Unit Mechanism—Pointing Accuracy Test Procedure, Setup and Results

The Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS) of the BEPI COLOMBO mission is dedicated to global mineralogical mapping and measurements of Mercury’s surface temperatures in the spectral range of 7–14 μm.MERTIS Pointing Unit (MPOI) is a mechanism situated in front of MERTIS spectrometer to orient the optical entrance of the instrument to 4 different targets sequentially. MPOI should fulfill very demanding requirements of pointing accuracy and repeatability in whole operating temperature range from −30 to +70 °C. To verify these requirements test set up and procedure of measurement were prepared. In this paper MPOI’s design and principles of operation will be presented. Moreover pointing accuracy test setup, test procedure and results will be showed.