ESA GNC Conference Papers Repository

AstroTerra programme, encompassing the SPOT 6 and SPOT 7 satellites, ensures continuity of the services provided since 1986 by the SPOT family in the areas of maritime surveillance, agriculture, mapping, defence and environmental conservation, with improved agility, reactivity, and imaging performances. This self-funded system is owned by Airbus Defence and Space, who is also the satellite commercial operator. Its space segment consists of two identical satellites, SPOT 6, launched in September 2012, and SPOT 7, planned to be launched in June 2014. Both satellites form a constellation of Earth-imaging satellites characterized by 1.5 m resolution, 60 km swath, and geolocation better than 15 m. AstroTerra programme also complements Pléiades Very High Resolution data services, being operated jointly by CNES and Airbus DS on the same orbit and encompassing the Pléiades 1A and Pléiades 1B satellites, launched in December 2011 and December 2012. Pléiades is the highest resolution civilian Earth observation system ever developed in Europe, offering imaging performances such as 0.5 m resolution, 20 km swath, and geolocation better than 10 m. The four satellites acquire worldwide data, with one panchromatic and four multispectral bands. SPOT 6 and SPOT 7 satellites draw on technological and operational innovations designed for Airbus DS product lines, but also inherited from the Pléiades constellation. Both satellites are in particular based on the versatile AS250 new generation avionics product, allowing to serve a wide range of LEO missions. AS250 Avionics offer multiple options for the AOCS, among which mainly the choice of the inertial actuators: classical Reaction Wheels or a cluster of 4 Control Momentum Gyroscopes (CMG). The CMG, developed by Airbus DS for Pléiades, enable very high agility performances. AS250 Avionics offers also the possibility to select a gyrowith or gyroless attitude estimation solution depending on the required system performance. The high level of system geolocation accuracy is ensured by using 4 fiber-optic gyroscopes (FOG from Airbus DS) and Star Trackers (STR from Sodern). The new generation of HYDRA APS-based STR has been flight proven onboard SPOT 6. Orbit determination and time tagging are calculated on board with a metric accuracy by the Doris navigator in the case of Pléiades, and with a 10 m class accuracy by the MOSAIC GNSS receiver from Airbus DS, in the case of SPOT satellites. After more than 5 cumulated years, the in-orbit performances exceed expectations. This paper gives a status of the CMG-based AOCS performance observed in flight on the three satellites Pléiades 1A, Pléiades 1B and SPOT 6 and focuses on the in-orbit performances of key technologies developed for these programmes, such as the CMG and the high performance FOG, as well as the in-orbit qualification of the AS250 Avionics achieved in the frame of SPOT 6 In-Orbit Tests, including gyroless attitude estimation.