Design and Manufacture of a Highly Reliable, Miniaturized and Low Mass Shutter Mechanism

This paper describes the development, manufacturing and testing of a lightweight shutter mechanism made of titanium for the MERTIS Instrument. MERTIS is a thermal infrared imaging spectrometer onboard ESA's future BepiColombo mission to Mercury. The mechanism is built as a parallelogram arrangement of flexible hinges, actuated by a voice coil. In a first test run, it was shown that the selected EDM processing led to the generation of titanium oxides and an oxygen-enriched surface layer on the substrate (so called α-case layer). In the revised version of the shutter, it was possible to manufacture the complex geometry by micro-milling and an adjacent pickling procedure. The adequacy of this approach was verified by lifetime and vibration testing. Introduction and Requirements The MERTIS instrument is a thermal infrared imaging spectrometer onboard ESA's future BepiColombo mission to Mercury. For the spectrometric data acquisition, a calibration signal that contains information about the instrument background radiation is required. This is performed by periodical acquisitions while the targets scene (i.e., planet radiation) is blocked. Therefore, a mechanical shutter is required to block the optical path from the planet view of the instrument. The main requirements for the shutter mechanism are specified in Table 1. Table 1: Shutter main requirements