The UAVSAR project, funded and managed by ESTO, has developed a new remote sensing instrument to measure and monitor various changing features on Earth’s surface. Built at the Jet Propulsion Laboratory, UAVSAR was designed to fly on an uninhabited, remotely-piloted aircraft such as the Northrop Grumman Global Hawk (shown above).
Today, UAVSAR is flying on demonstration and science flights aboard the NASA Gulfstream III, a piloted airplane. Additional funds provided through the 2009 American Recovery and Reinvestment Act are helping to transition the instrument to the long-range, high endurance Global Hawk UAV aircraft.
How It Works
UAVSAR is a fully-polarimetric L-band (24 centimeter wavelength) synthetic aperture radar with an actively scanned antenna that can be electronically steered to point at its target. The instrument is flown on repeat pass missions over an area of interest and the images are compared to determine what has changed in the intervening time – a process called repeat pass interferometry.
The key challenge in obtaining repeat pass interferometry measurements is ensuring that the airplane and the instrument make the repeat trip as close to the original flight line as possible. The UAVSAR system utilizes real-time differential GPS to determine the aircraft’s position to within 30 centimeters. A precision autopilot developed at NASA’s Dryden Flight Research Center uses the GPS data to control the aircraft’s flight path to within 5 meters. The GPS / Autopilot system, coupled with the UAVSAR’s electronically steered antenna, enables repeated airborne measurements that can be used to detect millimeter-scale changes in the topography.
The UAVSAR instrument has the potential to measure and monitor a wide range of rapidly changing features on Earth – from rapidly moving glaciers and changes in ice thickness to seismic activity and vegetation. UAVSAR is also well-suited for use as an airborne test bed for future radar technologies and algorithms.