Drone a useful tool for measuring polar ice sheets

Scientists studying the behaviour of the world's ice sheets successfully tested the use of a small, lightweight unmanned aerial vehicle (UAV) with integrated, light-weight radar to look through the ice and map the topography underlying rapidly moving glaciers.

Such measurements would be far too expensive and technically challenging to carry out with manned aircraft, but the light weight and small size of the vehicle and sensor enable them to be easily transported to remote field locations and the airborne manoeuvrability enables the tight flight patterns required for fine scale imaging.

"We're excited by the performance we saw from our radar and UAS (unmanned aircraft system) during the field campaign. The results of this effort are significant, in that the miniaturized radar integrated into a UAS promises to make this technology more broadly accessible to the research community," said Rick Hale, associate professor of aerospace engineering and associate director of technology for the Center for Remote Sensing of Ice Sheets (CReSIS) at the University of Kansas.

In a paper published in the journal IEEE Geoscience and Remote Sensing Magazine, researchers at the CReSIS report how they successfully tested the UAV at a field camp in West Antarctica, with support from the National Science Foundation's Division of Polar Programs and the State of Kansas.

The measurements were the first-ever successful sounding of glacial ice with a UAV-based radar and if further tests in the Arctic prove as successful, the vehicle could eventually be routinely deployed to measure rapidly changing areas of the Greenland and Antarctic ice sheets.

The drone has a takeoff weight of about 38.5kg and a range of approximately 100km, while the compact radar system weighs only two kilograms, and the antenna is structurally integrated into the wing of the aircraft.

The UAV can be used to collect data over flight tracks about five meters apart to allow for more thorough coverage of a given area.

Shawn Keshmiri, an assistant professor of aerospace engineering, said: "A small UAS also uses several orders of magnitude less fuel per hour than the traditional manned aircraft used today for ice sounding."

This advantage is of great benefit, the researchers point out, "in remote locations, such as Antarctica, [where] the cost associated with transporting and caching fuel is very high."

Concerns about global warming causing the vast polar ice sheets to melt mean that scientists and engineers are seeking quicker, less expensive ways to measure and eventually predict exactly what they are doing and how their behaviour may change in the future.

Until now, the lack of fine-resolution information about the topography underlying fast-flowing glaciers, which contain huge amounts of freshwater and which govern the flow of the interior ice, makes it difficult to model their behaviour accurately.

"There is therefore an urgent need to measure the ice thickness of fast-flowing glaciers with fine resolution to determine bed topography and basal conditions," the researchers write.

"This information will, in turn, be used to improve ice-sheet models and generate accurate estimates of sea level rise in a warming climate. Without proper representation of these fast-flowing glaciers, advancements in ice-sheet modeling will remain elusive."

With the successful test completed in the Antarctic, the researchers will begin analyzing the data collected during this field season, miniaturizing the radar further and reducing its weight to 1.5kg or less, and increasing the UAV radar transmitting power.

In the coming months, they will also perform additional test flights in Kansas to further evaluate the avionics and flight-control systems, as well as optimize the radar and transmitting systems.

In 2014 or 2015, they plan to deploy the vehicle to Greenland to collect data over areas with extremely rough surfaces and fast-flowing glaciers, such as Jakobshavn, which is among the fastest flowing glaciers in the world.