Time and frequency domain characterisation of the Metis: Solar Orbiter coronagraph

Metis is the ultraviolet–visible coronagraph on board the ESA Solar Orbiter mission, designed to image the solar corona simultaneously in polarised visible light and in the Lyman-α ultraviolet emission. The instrument can acquire full-frame images on both channels at a very high rate, with a minimum cadence of one second. This capability enables detailed investigations of coronal variability and fluctuations, but also requires an accurate characterisation of the instrument response in both the time and frequency domains. In this work, we present the methodology adopted to assess the temporal and spectral variability of the response of the Metis detectors. In particular, we identify and analyse the main sources of signal variability due to instrumental effects, with the aim of quantifying their impact on the measurements and decoupling them from the intrinsic physical fluctuations of the solar corona.