A stormy night, a small plane crashes in the mountains. The search can't start until daylight, and the bad weather may cause more delays. Even when the search can begin, the plane may be hidden beneath trees or brush and almost impossible to spot from the air. Heavy vegetation and steep hillsides may limit ground searches.
In the future, NASA-developed radar may be able to help. JPL scientists and engineers are working with NASA's Search and Rescue Misson Office, based at Goddard Space Flight Center, Greenbelt, Md., to see if Airborne Synthetic Aperture Radar (Airsar) may be able to detect possible crash sites. If it can, then the technology could potentially be used to develop a smaller, less expensive sensor specifically designed for search and rescue use.
Designed and built at JPL, the two-ton Airsar instrument flies on NASA's DC-8, based at Dryden Flight Research Center, Edwards, Calif. Since 1988, it has been used for a variety of studies from measuring snow and ice in the Colorado Rockies to imaging volcanoes in the Pacific. The side-looking radar can penetrate through clouds and forest canopy and can operate both day and night.
Last month, the instrument, along with a crew of 20, flew a pre-determined path over a 579-square-kilometer (360-square-mile) area in California's San Bernardino National Forest as part of an experiment arranged by the NASA Search and Rescue Mission Office in conjunction with the county sheriff's department. On the ground, ten 1.8 meter (6-foot) and 2.4 meter (8-foot) high aluminum corner reflectors served as targets, which will appear as bright man-made objects in the processed radar data. Other targets were damaged airplane parts placed under trees in the flight path.
In addition to the known targets, researchers are also very interested to see if they will be to detect the wreckage of a small plane lost in the area in May 2001. Though extensive air and ground searches were conducted, the plane has not been found. The radar data is still being processed, so the results won't be known for several weeks.
In an earlier experiment, Airsar flew over a 161-square-kilometer (100-square-mile) area in the mountains of Montana where another small plane had been lost and never found. After processing the radar data, the Search and Rescue Mission Office identified fourteen potential crash sites. A search team found the wreckage near one of the locations.
NASA's Search and Rescue Mission Office is investigating several kinds of search and rescue technology. One includes improvements to the beacons that are detected and located by the successful Cospas-Sarat satellite system. Another is putting compatible equipment on future global positioning system (GPS) satellites so that it may be possible to locate a distress beacon almost instantly.
However, satellite systems work only when distress beacons survive a crash. The Search and Rescue Mission Office is studying remote sensing, such as synthetic aperture radar, as an alternative search method in remote areas when no distress beacon is operating. Because it can "see" through trees, brush and cloudy weather, it may be able to find a crash site when a visual search cannot. Someday, radar could be carried aboard a search aircraft, an unmanned aerial vehicle or even a satellite.
"Airsar is NASA's testbed for demonstrating and testing new radar technology," said JPL's Dr. David Imel, principal investigator for the instrument. "While Airsar is not the right sensor to do operational search and rescue missions -- it's not typically available on a moment's notice, it doesn't have a real-time search and rescue processing capability, and its radars are not designed optimally for search and rescue -- it may serve as an invaluable tool for the design and development of a successful operational system."