Washington, Dec 31 (IANS): A group of researchers has sent radio signals into space with the purpose of bouncing them off a 500-feet asteroid to learn about its interior.

The High Frequency Active Auroral Research Programme (HAARP), a powerful transmitter in remote Alaska, aimed its antennas at asteroid 2010 XC15, a space rock categorised as a near-Earth potentially hazardous asteroid, to send long wavelength radio signals.

The results of the experiment could aid efforts to defend Earth from larger asteroids that could cause significant damage.

"We will be analysing the data over the next few weeks and hope to publish the results in the coming months," said Mark Haynes, lead investigator on the project and a radar systems engineer at NASA's Jet Propulsion Laboratory in Southern California.

This experiment was the first time an asteroid observation was attempted at such low frequencies.

"This shows the value of HAARP as a potential future research tool for the study of near-Earth objects," he added.

Several programmes exist to quickly detect asteroids, determine their orbit and shape and image their surface, either with optical telescopes or the planetary radar of the Deep Space Network, NASA's network of large and highly sensitive radio antennas in California, Spain and Australia.

Long wavelength radio signals can reveal the interior of objects.

HAARP, using three powerful generators, began transmitting chirping signals of long wavelength this week and continued sending them uninterrupted until the scheduled end of the 12-hour experiment.

Data analysis is expected to take several weeks.

The experiment also served as a test for probing an asteroid larger than 2010 XC15.

Asteroid Apophis, discovered in 2004, will make its closest approach to Earth on April 13, 2029. It will come within about 20,000 miles of Earth, closer than the many geostationary satellites orbiting the planet.