Metis Coronagraph–Flight Model under Acceptance Tests

Metis, an inverted-occultation coronagraph, is one of the most relevant remote sensing instruments of the Solar Orbiter mission of the European Space Agency (ESA). Metisis the only coronagraph ever designed to acquire simultaneous images of the solar corona in two different wavelengths (visible light between 580 nm and 640 nm, and the Lyman-α line of Hydrogen at 121.6 nm). The visible channel also includes a polarimeter to observe the linearly polarized component of the K corona.The Qualification Reviews of the coronagraph under responsibility of the Italian industries OHB-I and Thales Alenia Spacein Italy(TAS-I) and of the visible and ultraviolet light detector assemblies (VLDA and UVDA) developed by the Max Planck Institute for Solar System Research in Göttingen, Germany, were successfully concluded in 2016. The main optics, in particular the mirrors that are under the responsibility of the Astronomical Institute of the Academy of Sciencesof the Czech Republic have beenalso qualified at sub-system level.The main elements (UVDA, VLDA, Mirrors, Polarimeter, etc.) have beenfinally integrated in the coronagraph along with the Metis Processing and Power Unit(MPPU), High Voltage Unit(HVU)and Camera Power Converter(CPC)in the OPSys facility at ALTEC in Turin, Italy.The entrance of the telescope will be protected bya sealing protection cap, designed under the responsibility of the Spanish company SENER to be compliant with the very stringent and challenging contamination requirements and to be ejected once in orbit. The vibrations,thermal-vacuum and EMC acceptance tests for the Flight Model of the integrated system have beensuccessfully completed. After thesetests, the activities of calibration of the instrumenthave beencarried out by the MetisScientific Team and TAS under the responsibility of the Principal Investigator, Prof. E. Antonucci.On May 2017, the flight model of Metis has been delivered for being integrated on Solar Orbiter.