RADAR "SAIL" satellite concept and design

The RADAR SAIL concept is based on the use of a rectangular antenna lying i n the dawn-dusk orbital plane with the length (along speed vector) smaller than the height. Such geometry makes it possible to place the solar cells o n the back of the antenna, to use gravity gradient stabilisation, and (opti onally) to implement multipath-free GPS interferometric measurement of the antenna deformation thus allowing structural relaxation. Less obviously, th e geometry favours the RADAR design too, by allowing grating lobes and ther efore a lower density of built-in electronic in the active antenna. The ant enna can be thin and packed for launch inside a cylinder-shaped bus having pyrotechnic doors for the antenna deployment and bearing the rest of the pa yload and the service equipment. With respect to a standard design of high performance missions, cost savings come from the bus, whose functions (AOCS , power supply) are simplified, from the launch since the mass budget and t he stowing configuration become compatible with medium size rockets (LLV2/3 , DELTA-LITE, LM-4...), and from the active antenna built-in electronics. M oreover, long satellite life-time can be achieved (10 years instead of 5). The RADAR SAIL concept is ail the more cost effective when the mission requ ires a large, high and short antenna, i.e. high resolution (< 5 m), low fre quency band (L or S or even P), high revisiting, multiple frequencies. Miss ion implementation and funding can be favored by the new capability to shar e the satellite between autonomous regional operators. Combined with ground DBF (digital beam forming) technique, the concept allows extremely simple and low cost missions providing a fixed wide swath (10 to 15 m resolution w ithin 500 km to 1000 km swath) For systematic surveillance or monitoring. ( C) 2000 Elsevier Science Ltd. All rights reserved.