PROTEUS PLATFORM : JASON1 FLIGHT RESULTS, DESIGN EVOLUTION FOR FUTURE MISSIONS, NEXT APPLICATIONS

In collaboration with the French National Space Agency CNES, ALCATEL SPACE has developed PROTEUS (plate-forme reconfigurable pour l'Observation, les telecommunications, et les usages scientifiques), a multipurpose LEO platform in the range 500 kg. PROTEUS AOCS has been designed to comply with any kind of pointing: inertial, solar, Earth, anti-Earth or nadir. JASON1 satellite, a CNES/NASA-JPL oceanographic mission, is the first PROTEUS application as follow-on of the TOPEX-POSEIDON mission. JASON1 was successfully launched on December 7th, 2001 from Vandenberg, California. JASON1 being on-station for 2 years, a large quantity of data has been collected allowing to present with some details the behavior of the PROTEUS AOCS during this period. Algorithms and equipment units are discussed, with a special focus on the STR. To cope with future missions, modifications to PROTEUS generic AOCS have been assessed mandatory. The main evolution of future missions is the increase of the payload size. This impacts mostly the safe hold mode which is based on magnetic actuation; convergence duration towards Sun pointing is a critical issue. In addition, taking experience of JASON1 flight results, a global discussion was engaged with CNES to improve the platform performances. Description and justification of these modifications are detailed. Following JASON1 success, new PROTEUS based missions have been ordered by CNES: (1) CALIPSO is a CNES/NASA mission devoted to Earth atmosphere observation. (2) COROT satellite (COnvection, ROtation et Transits planetaires), a CNES mission, is dedicated to asterosismology and research of exoplanets. (3) SMOS satellite (soil moisture and ocean salinity), a CNES/ESA mission, improves our understanding of climatic phenomena, particularly the water cycle at the Earth's surface. (4) JASON-2 is a follow-on mission of JASON1.