A low-cost imaging radar: DRIVE on board ONERA motorglider

UAVs from different countries and with different payloads have proven their capabilities within military applications. Future UAV employment in the civilian areas of surveillance (pollution, natural risks prevention, fire prevention), monitoring (traffic control, environmental monitoring, earth observation) and communication relays becomes unavoidable. Many payload configurations may be used in UAV operations, but compared to systems working in other spectral regions (such as optical or infrared sensors), radar has the main advantage to be able to operate in all-weather condition. A concept of low-cost imaging Ka-Band radar is presented in this paper. This radar is integrated into under-wings pods that are fixed on a STEMME S10VT motorglider. This radar concept combines real aperture in the cross-track direction, by the antennas geometrical aperture, and synthetic aperture in the along-track direction, realized with the aircraft motion. Radar front-end uses FMCW technique which allows to reduce the power emission to a few Watts. In addition, the use of the millimeter band induces antennas size reduction, and makes possible the radar integration into pods. Thus, radar particularities are a low-size, a low-weight and a low-cost basis, making this radar suitable for future integration on board small vehicles, such as UAV. The radar definition and specifications will be detailed, together with the first results obtained on Fall 2006. Two ways of operating the radar will be presented: An application as vertical sounder, using horn antennas, and an application as SAR radar, using rectangular antennas. The two cases will be illustrated by samples of acquisitions results. The DRIVE radar has been developed and built to fly on board an UAV vehicle. Indeed, this radar is designed and will be used by ONERA as a UAV radar test bench. Current airplane used for testing applications is a STEMME S10-VT motorglider as the geometry of this airplane may be representative of a MALE UAV: wingspan is 23 m large and weigh is about 900 kilograms. DRIVE Project started at ONERA on January 2005, and first flights happened in the beginning of 2006. DRIVE radar uses FMCW techniques and operates in Ka Frequency Band: Central frequency is 35 GHz and bandwidth is about 800 MHz width.