NASA?s ICESat (Cloud and Land Elevation Satellite) quit working in 2009, but data collection is now being achieved by radar on IceBridge flights which survey Earth’s polar ice. Mapping bedrock beneath the Antarctica ice cap has proved to be a tricky maneuver for students, scientists, and engineers working together at the University of Kansas.
Radar comes in many different frequencies and finding the right one to penetrate ice to the subglacial rock and send the data back has been a challenge. The research is attempting to determine how terrain concealed below the deep ice pack affects how the ice moves and how that contributes to sea levels.
The action is taking place at the Center for the Remote Sensing of Ice Sheets (CReSIS), a National Science Foundation-funded center at the University. Maintaining the fondness for synonyms, the mapping radar the scientists are using is known as the Multichannel Coherent Radar Depth Sounder or MCoRDS.
Data from MCoRDS of ice surface, internal layering, and bedrock (jagged line at bottom of image) on last month?s IceBridge survey. Credit: Theresa Stumpf, CReSIS
Radar radio waves are sent out and their timed return functions unimpeded through air, but thicker materials such as rock act almost like mirrors. Capturing valid information takes know-how. The team determined that low frequency, between 120 and 240 MHz, not high frequency radio waves, work best when dealing with ice.
MCoRDS?s underwing radar antenna arrays mounted beneath the wing of NASA?s P-3 aircraft. Credit: George Hale, NASA
A 15 antenna array mounted on a NASA P-3 underwing surveys large areas and records several signals at once providing a relatively clear picture. MCoRDS?s array routes returning radar pulses to a receiver, then it is recorded on solid state drives on the plane. Up to two terabytes per flight can be recorded, then downloaded, archived, and backed up by personnel at the University of Indiana.
CReSIS researchers use tomography with specialized computer software to calculate the position and distance of signals returned from the bedrock. From this they can create a 3D look at it. New maps of Greenland illustrate a previously unknown 460 mile (750 kilometers) canyon under the ice sheet that reaches 2,600 feet (800 meters) deep.
Research will continue in the future, possibly via unmanned aerial vehicles similar to NASA’s Global Hawk, greatly increasing the amount of terrain that can be covered from the air.