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Design and qualification of the STREEGO multispectral payload

The increasing number of Earth Observation missions launched over the last decade has stimulated the development of a large number of satellite instruments able to acquire and deliver rich imageries suitable to support many different applications. Recent advances in electronics, optical manufacturing and remote sensing are now enabling the conception of smaller instruments that could enable new mission concepts at lower costs such as the adoption of satellite constellations for improved temporal resolution. In this paper we present the development of an innovative optical payload named STREEGO suitable for Earth Observation from Low Earth Orbit (LEO) microsatellites. STREEGO is an athermal, fully reflective telescope based on a three mirror anastigmat (TMA) design which features a 200 mm aperture, a focal length of 1.2 m and an across-track Field of View (FoV) of about 2°. Leveraging on a large format two-dimensional CMOS sensor with a pixel size of 5.5 μm, it delivers a nominal modulation transfer function (MTF) of 64% at Nyquist frequency and a ground sampling distance of 2.75 m from an altitude of 600 km. In the design of the instrument detailed stray-light and tolerance analyses were performed and a worst-case thermal model was also developed to ensure that optimal image quality is achieved under operational conditions. After preliminary tests on a Demonstrator Model (DM), an Engineering Model (EM) of the payload with a mass of 20 kg including its electronics and mounting interfaces has been integrated and tested in laboratory and it is now ready to start an environmental test campaign to increase its Technology Readiness Level (TRL). The qualification of the instrument and the results achieved are presented in detail.