METIS, the Multi Element Telescope for Imaging and Spectroscopy: an instrument proposed for the solar orbiter mission
METIS, the Multi Element Telescope for Imaging and Spectroscopy, is an instrument proposed to the European Space Agency to be part of the payload of the Solar Orbiter mission. The instrument design has been conceived for performing extreme ultraviolet (EUV) spectroscopy both on the solar disk and off-limb, and near-Sun coronagraphy and spectroscopy. The proposed instrument suite consists of three different interconnected elements, COR, EUS and SOCS, sharing the same optical bench, electronics, and S/C heat shield aperture. COR is a visible-EUV multiband coronagraph based on a classical externally occulted design. EUS is the component of the METIS EUV disk spectrometer which includes the telescope and all the related mechanisms. Finally, SOCS is the METIS spectroscopic component including the dispersive system and the detectors. The capability of inserting a small telescope collecting coronal light has been added to perform also EUV coronal spectroscopy. METIS can simultaneously image the visible and ultraviolet emission of the solar corona and diagnose, with unprecedented temporal coverage and space resolution the structure and dynamics of the full corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙, measured from Sun centre) at minimum (maximum) perihelion during the nominal mission. It can also perform spectroscopic observations of the solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region, and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125 nm spectral band.