'Learn to love the asteroids'

2002-08-03 11:57

Berlin - It is time to stop worrying and learn to love asteroids - or at least learn to love watching for them, according to scientists in Germany who have come up with an ingenious plan for spotting "invisible" asteroids long before they pose a threat to Earth.

These experts are self-confessed asteroid lovers, men and women who have devoted their scientific careers to the pursuit of these elusive cold clumps of stone tumbling through space.

Who else but someone who really loves asteroids would gather in Berlin for a scientific congress on near-Earth objects in the dog days of summer when everyone else in Europe heads for the mountains or the beaches?

What got these experts steamed up during their conference was not a summer heat wave which had Berliners panting, but rather tabloid headlines proclaiming that an asteroid was "on a collision course" and could wipe out a continent on Earth in the year 2019.

"This is just utter rubbish," said asteroid-ologist Alan W Harris, an asteroid studies researcher at Nasa's Jet Propulsion Laboratory (JPL), who was in town for the conference.

The asteroid, discovered July 9 and dubbed 2002 NT7, was not and is not "on a collision course", he and the other experts insisted, but rather it had a very, very small chance of being on a collision course. With scientific precision, they calculated that risk to be 3.9-in-a-million.

Frustrated and fuming, the people who know asteroids best call it misleading and unethical for the media to play up doom-and-gloom stories.

"The number of near-Earth asteroids larger than 1 kilometre in diameter is currently about 1 200. To date, almost half of them have been discovered," Harris told the conferees in Berlin. "Much less is known about the smaller objects."

'We could still be caught off guard'

Asteroids measuring only a few hundred metres in diameter could still pack enough punch to wipe out a major city, Harris warned. And one with a diameter of just a few kilometres could ultimately result in the extinction of most life forms on the planet.

"But if we are able to spot an asteroid sufficiently ahead of time, say 20 to 30 years in advance, we can take steps to avert catastrophe," Harris said.

"We could still be caught off guard," Harris warned, saying that "invisible" asteroids could come straight toward the earth from the direction of the sun - the solar glare making them "invisible" to us until it is too late. And such "Inner Earth Objects" are bound to be out there and heading toward us.

"The question is just how and when," he said.

And that is where the Earthguard I project comes in. Being launched this summer by the Munich-based aerospace company Kayser- Threde and the German Aerospace Center (DLR) in Berlin, Earthguard I is one of the studies the European Space Agency (ESA) has selected for the preparation of new space missions for the study of Inner Earth Objects, which the experts call IEOs.

While these objects can occasionally come very close to our planet, they are very difficult to detect from Earth because this particular observing geometry places them at small angular distances from the Sun for most of the time, making them invisible against the bright sky background.

The Earthguard I mission overcomes this problem by making use of a compact search telescope mounted on a spacecraft in a heliocentric orbit in the inner Solar System.

From this vantage point, not only would IEOs be more easily detected against a dark sky background, but they would also appear brighter due to the smaller solar phase angle, the same way the full moon appears much brighter than the crescent moon, says Stefano Mottola of the German Aerospace Centre.

In this way such an instrument could detect objects down to about 100m, accurately determine their orbits, estimate their size, and establish their orbital and size distribution.

"All these parameters are of crucial importance not only for their scientific interest, but also for better understanding the hazard those objects pose to our civilisation," according to Mottola.

"For this reason this space-based detection system is to be seen as integrating and complementing the activities performed by the ground-based search programs."

The mission could be aloft by the end of this decade, he says, either using a dedicated spacecraft, or, alternatively, flying "piggy-back" on a platform planned for other studies, as a Mercury or a Venus orbiter.

And with Earthguard 1 in place, asteroid-watchers will be able to scan the heavens to their hearts' content - giving us all a better chance at avoiding being blind-sided from space. - Sapa-DPA

- SAPA