PRISMA calibration based on natural targets

PRISMA is the hyperspectral mission from the Italian Space Agency (ASI) launched in 2019. It samples the solar irradiance reflected and diffused by the earth-atmosphere system between 400 nm and 2500 nm with a spectral distance better than 11nm and a 30m Ground Sampling Distance. To answer the demanding need of hyperspectral applications, a high absolute radiometric accuracy is required and reached through the combination of on board and natural targets based calibration. This paper describes PRISMA mission and focuses on the natural targets based calibration methods used to assess the instrument sensitivity. Two methods are used: - PICS (Pseudo Invariant Calibration Sites) allow to cross-calibrate PRISMA with SENTINEL-2 and 3 ESA missions. - Gobabeb and La Crau Instrumented sites known as RadCalNet sites which provide a BOA spectral BRDF through a dedicated acquisition protocol and processing as well as atmospheric parameters simultaneously to the satellite pass. The adaptation of these methods to hyperspectral sensors calibration is presented. The calibrations results which show the very good temporal stability of PRISMA instrument are discussed as well as the methods and in situ instrumentation evolutions planned to improve the calibration of hyperspectral sensors using natural targets.