Battlefield awareness" is critical to the success of future military operations. Existing and new sensor platforms will provide the necessary surveillance data; DARPA is developing the systems needed to turn the sensor data into meaningful information for the commanders. A central thrust of these efforts exploits the synergistic relationship between SAR and MTI radar. Used together, they offer comprehensive coverage of the battlefield. THE REQUIREMENT FOR WIDE-AREA SURVEILLANCE To prevail in the diverse arenas of future conflicts, the United States and its allies must achieve "dominant battlefield awareness" which means, simply stated, a knowledge of everything occurring on the battlefield [1]. To apply their assets optimally, the commanders in the theater must know the locations, identities and, ideally, the intentions of the enemy forces. The challenge to the R&D community is to develop the systems and technologies to provide battlefield awareness [2]. Sensors, of course, generate the data about events on the battlefield, and radar, in particular, must play a major role because of its day-and-night, all-weather capability [3,4]. Synthetic Aperture Radar (SAR) can provide high-resolution imagery of stationary objects. Moving Target Indicator (MTI) radar can detect and locate moving targets. Working together, they offer the potential for comprehensive coverage of vehicle targets on the battlefield. The primary distinctions between the historical use of sensors, in reconnaissance roles, and tomorrow's surveillance needs are: (1) the size of the areas that must be searched; (2) the sensor resolution required; and (3) the rapidity and frequency with which the search must be done. To support battlefield awareness, sensors will be asked to cover regions larger than 400 km on a side at high resolution, with a revisit time of significantly less than an hour. We label an operation of this scale "wide-area surveillance". During Desert Storm, the U.S. and its Coalition allies stressed the limits of existing sensor systems by attempting to perform wide-area surveillance of the vast Iraqi desert. The U-2 and Joint STARS 1 were employed in the theater to gather the needed information. Although significant intelligence needs were met by the surveillance operation, serious deficiencies were
