Poseidon altimeter--a satellite-based radar altimeter compatible with small-satellite missions: features and in-orbit performances

ALCATEL ESCAPE, France, has designed, developed and manufactured a radar altimeter for CNES, the French Space Agency. This altimeter was integrated onto the TOPEX POSEIDON satellite as part of a cooperative program between CNES and NASA. TOPEX POSEIDON was successfully launched on 10 August 1992 by an ARIANE-4 rocket and the CNES/ALCATEL ESPACE altimeter turned on 21 August for the first time. Since then, the altimeter has been operated 15% of the time, the remaining 85% being dedicated to the NASA supplied APL altimeter (both altimeters share the same antenna and operate at the same frequency). Analysis of collected data have demonstrated exceptional performances of ALCATEL ESPACE altimeter. This paper includes the presentation of the altimeter objectives, the altimeter basic characteristics, and the in-flight measured performances. The low weight, low power, low TM rate and low cost altimeter was specifically designed to be flown on any satellite platform, including small satellites. A project of a small satellite using the ALCATEL ESPACE altimeter is also presented.