Preliminary design of a combined Ka-band altimeter and dual frequency radiometer

In preparation of the post ENVISAT and Jason-2 altimetry missions, Alcatel is currently studying in phase A for CNES a new class of altimeter. A major objective is to propose a combined altimeter and radiometer at minimum cost, size and power consumption compatible with a micro-satellite (<100 kg class). The micro-satellite(s) would be used to improve the spatial/temporal sampling of the ocean which is not sufficient for current and future oceanographic missions. For a given antenna size, the Ka band (35 GHz) is more interesting than the Ku band for the altimeter since it improves the link budget and allows larger bandwidth (500 MHz). From the scientific point of view, Ka-band altimeter data would give access to a different part of sea surface roughness spectrum and thus would complement the C+Ku measurements available from other altimeters. The microwave radiometer, used for wet path delay correction, is a dual-frequency instrument (23.8 and 36.8 GHz). This paper presents the altimeter and radiometer required performances and the overall instruments design. Preliminary results from the breadboarding activities are also reported.