Metis/Solar Orbiter Observation of Comets

The Metis coronagraph on-board the Solar Orbiter mission, focused on the study of the solar corona, has also detected also near-Sun comets in the first two years of observations. Metis observes comets passing into the field of view covering an annulus between 1.5° and 2.9° centered in the Sun direction, with a spatial resolution of 20 arcsec, the corresponding imaged heliocentric distance ranges from 1.6 to 12 Solar Radii depending on the spacecraft distance from the Sun. The two instrument channels, UV narrow band HI Lyman- at 121.6 nm, and the polarized broad-band visible light (580 - 640 nm) can be operated with high cadence, then, for the first time, Metis allows simultaneous observation of 2D comet images both in the visible and in the UV emission. These observations provide direct information on cometary parameters (e.g. water outgassing rate, coma and tail composition, fragmentation) and allow to constrain the physical parameters of the coronal plasma encountering the comet (e.g. electron density and solar wind velocity). Collaboration with currently operational missions (in particular SOHO and STEREO) allows to improve the stereoscopic description of observed comets and to determine more accurately the orbital parameters. Based on studies from SOHO observations, we expect to regularly observe comets. A project is underway to systematically research the comets detected by Metis. In this paper, we present the first results obtained with the observations of the long period comet C/2021 A1 (Leonard), and two sungrazing comets observed on September 2nd and December 24th, 2021.