Metis aboard the Solar Orbiter space mission: Doses from galactic cosmic rays and solar energetic particles

The aim of this work is to calculate the dose released by galactic cosmic rays (GCRs) and solar energetic particles (SEPs) in the polarimeter of the Multi Element Telescope for Imaging and Spectroscopy (METIS) coronagraph [1] aboard the Solar Orbiter. This investigation is performed with a Monte Carlo method by considering the role of SEP events of proper intensity at a heliocentric distance from the Sun averaged along the spacecraft orbit. Our approach can be extended to other space missions reaching short distances from the Sun, such as Solar Probe Plus. This study indicates that the deposited dose on the whole set of polarimeter lenses and filters during ten years of the Solar Orbiter mission is of about 2000.Gy. For cerium treated lenses, a dose of 10⁶.Gy of gamma radiation from a ⁶⁰Co source causes a few percent transmittance loss.