PROSE: a low cost P band transponder radar satellite based on the SAIL concept

The SAR (P)ROSE satellite concept is based on the following principles: fixed transmit beam covering a wide elevation range, direct relay to ground of the echoes received by each antenna radiator, narrow receive beam formed on ground in all elevation directions (Digital Beam Forming). It provides a fixed and permanent wide swath (300 to 500 km) at low or medium resolution (>10 m) with a very simple communication transponder type payload stripped of signal, diagram control and of ground scheduling. The costs can thus be kept very low. The concept allows Radar Observation on Systematic (always on, no scheduling) and Economical way (ROSE). It fits applications requiring systematic and frequent (3 to 6 days) acquisition on large area with nevertheless rather good resolution (up to 20 MHz bandwidth) (e.g.: ice and navigation, ships and pollution, hydrology, biomass monitoring). Such combination of operational performance (huge swath/pixel ratio) and simplicity (transponder) is made possible by the use of the RADAR SAIL original satellite architecture, which, among other things, reduces the number of antenna radiators and thus the number of transponded return channels, and suppresses the nadir echo. Applied to P band, (P)ROSE becomes even more exciting since for the first time large swath become possible in P band, thanks to the ROSE approach and to the SAIL concept capability for very large antenna (50 to 100 m/sup 2/) under limited fairing size. This mission opportunity is all the more exciting that it is costly to attain with conventional means and difficult to achieve even with emerging technologies (such as inflatable antennae).