U.S. scientists use flying radar system to study earthquakes

The device, the Uninhabited Aerial Vehicle Synthetic Aperture Radar is currently being used on a human-piloted plane, mounted on the plane shoots long-wavelength radar beams at features on the ground and measures the reflections.

After the tragic earthquake that hit the picturesque valleys of Azad Kashmir and Kaghan, succeeding the tremors that shook the capital resulting in crumbling down of Margalla Towers in Islamabad, the people learnt that the areas fall directly on the fault line.

The consequent loss of human life and damage to almost everything important for sustaining life in affected areas, the Pakistanis learnt for the first time what a terrible earthquake can do to us. Accordingly an interest arose in the hitherto unknown or scantly known field of seismography.

It is said that the knowledge of seismography has seen lot of advancement in last few decades, yet it’s still not possible despite the advances in the science and technology of these fault lines, to predict or forecast an occurrence of earthquake / s in a particular city, region or a country.

But efforts indeed have been going on involving experiments using different techniques to enable us predict the possibility of an earthquake in a particular topographic area or zone.

UAVSAR is such project, which is funded and managed by the Earth Science Technology Office. It 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, remote-piloted aircraft such as the Northrop Grumman Global Hawk. Currently, it is being flown on demonstration and science flights aboard the NASA Gulfstream III, a piloted airplane.

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 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 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. The system is also well-suited for use as an airborne test bed for future radar technologies and algorithms.

Scientists are now using the new radar imaging system on the belly of a Gulfstream jet to track California’s earthquake faults.

Flying over California’s complicated network of faults, the system has started collecting some of the most detailed images yet of the Earth’s surface shifting and straining with seismic energy, says the Los Angeles Times, quoting scientists at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Los Angeles.

“This will show us where the faults are active,” said Andrea Donnellan, a JPL geophysicist who is one of the project’s principal investigators. “Where the ground is moving tells us what’s going on at depth.”

The data from this project could help scientists figure out where the risk of earthquake activity is highest, though the data will never be so specific as to predict a day, location and magnitude of a quake, she said.

“This will help us with the five- to 10-year time horizons,” Donnellan said. “We can see hot spot maps and … figure out whereto target our retrofitting.”

Based at NASA’s Dryden Flight Research Center at Edwards Air Force Base, the plane flies about 45,000 feet above the ground along GPS-guided trajectories.

The project will map faults across about 70 percent of California, including a wide swath of Southern California, said the project’s chief scientist, Scott Hensley.

It also will fly for other projects, such as studying glacier motion in Greenland. The first images were collected in December, but have not yet been fully processed.

Developing the technology, modifying the plane and collecting data for the first year will cost about 30 million dollars, Hensley said.

Satellites operated by other countries have collected radar data on surface deformation for years, but most don’t use the long-wavelength radar that enables the NASA device to penetrate vegetation and focus more on the hard ground surface, said Paul R. Lundgren, another principal investigator on the project.

A plane is also able to fly much closer to the ground than a satellite orbiting in space, improving the resolution by a factor of 10, he said.

Source: Mathaba.net

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