The problem is that the efforts are still in their infancy, all while these objects continue to be in the path of the Earth's orbit.
One such object struck the planet on October 8th over Indonesia. A report indicates that it struck with a force of 50,000 tons of TNT, or the equivalent of a medium-sized nuclear blast. The nuclear weapon that detonated over Hiroshima was smaller than the energy released by this:
No telescope spotted the asteroid ahead of its impact. That is not surprising, given that only a tiny fraction of asteroids smaller than 100 metres across have been catalogued, says Tim Spahr, director of the Minor Planet Center in Cambridge, Massachusetts. Yet objects as small as 20 or 30 metres across may be capable of doing damage on the ground, he says.Movies like Armageddon and Deep Impact warn of the threat of planet-killers, but those objects are easier to spot than the far more numerous smaller objects that could potentially ruin the day of a city or region.
"If you want to find the smallest objects you have to build more, larger telescopes," says Spahr. "A survey that finds all of the 20-metre objects will cost probably multiple billions of dollars."
The US Office of Science and Technology Policy, which advises the White House, must develop a policy to address the asteroid hazard by October 2010 under a deadline imposed by 2008 legislation. It is likely to be influenced by a report from the National Research Council on the asteroid problem, which is expected by year's end.