Spectralon diffusers used as in-flight optical calibration hardware

The medium resolution imaging spectrometer (MERIS), developed under European Space Agency (ESA) contract, for the Envisat 1 Polar Orbit Earth Mission belongs to a new generation of Ocean Color sensors which aim to improve the knowledge of some crucial processes of our planet. The instrument currently in the final stages of development is built by an international team led by AEROSPATIALE under ENVISAT prime contractor-ship of DORNIER. MERIS is a 'pushbroom' type instrument which measures the radiance of the Earth in 15 programmable spectral bands between 390 nm and 1040 nm over a 1150 km swath width. During the duration of the MERIS mission, radiometric in-flight calibration sequences are carried on a regular basis by the observation of Spectralon diffusers illuminated by the sun. The high accuracy required over the 4 years mission duration necessitates the precise knowledge of the calibration reference and the stability of the reference over the mission has to be controlled. This presentation details the influence of cleaning procedures on optical stability of the Spectralon flat plate diffusers calibration reference under space conditions and sun illumination. This paper will also define the BRDF characterization performances achieved with the Flight Model flat plate diffusers following implementation of the selected cleaning procedure.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.