First-light Observations of the Metis Solar Coronagraph

Metis coronagraph is one of the remote-sensing instruments of the Solar Orbiter mission launched in February 2020. The mission profile will allow for the first time the remote-sensing observation of the Sun from as close as 0.28 Astronomical Units (AU) and from ecliptic latitudes as high as 30°. Metis, in particular, is aimed at the study and the overall characterization of the solar corona and solar wind. This instrument is an innovative inverted-occultation coronagraph that will image the solar corona for the first time simultaneously in two different wavelength band-passes: in the linearly-polarized visible-light (VL), between 580 and 640 nm, and in the ultraviolet (UV) HI Lyman-? line of hydrogen, at 121.6 nm. The visible channel includes a broad-band polarimeter to observe the linearly polarized component of the K corona. These measurements will allow a complete characterization of the physical parameters, such as density and outflow speed, of the two major plasma components of the corona and the solar wind: electrons (protons) and hydrogen. After a period of commissioning, by the summer of 2020, Metis has performed the First-light Science Observations during the "Remote-Sensing Check-out Window" (RSCW) that is a telemetry contact period, specifically allocated before entering the operational phase at the end of 2021. This paper reports the first-light science observations of Metis represented by the UV and polarized VL images of the corona. The resulting first-light maps of the coronal electron distributions are presented. These results are compared to the observations of the visible-light ground-based coronagraph K-Cor and the visibleligh coronagraph LASCO onboard SOHO mission orbiting on the Lagrangian-1 Point and therefore offering a different viewpoint of the solar corona with respect to Solar Orbiter.