Multi Element Telescope for Imaging and Spectroscopy (METIS) coronagraph for the solar Orbiter mission

METIS, the “Multi Element Telescope for Imaging and Spectroscopy”, is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission to be launched in 2017. The unique profile of this mission will allow 1) a close approach to the Sun (up to 0.28 A.U.) thus leading to a significant improvement in spatial resolution; 2) quasi co-rotation with the Sun, resulting in observations that nearly freeze for several days the large-scale outer corona in the plane of the sky and 3) unprecedented out-of-ecliptic view of the solar corona. This paper describes the experiment concept and the observational tools required to achieve the science drivers of METIS. METIS will be capable of obtaining for the first time: ∙ simultaneous imaging of the full corona in polarized visible-light (590-650 nm) and narrow-band ultraviolet HI Lyman α (121.6 nm); ∙ monochromatic imaging of the full corona in the extreme ultraviolet He II Lyman α (30.4 nm); ∙ spectrographic observations of the HI and He II Ly α in corona. These measurements will allow a complete characterization of the three most important plasma components of the corona and the solar wind, that is, electrons, hydrogen, and helium. This presentation gives an overview of the METIS imaging and spectroscopic observational capabilities to carry out such measurements.