An Earth-bound asteroid or comet could still kill us but thanks to powerful telescopes slated for addition to the worldwide detection effort, we may be able to actually see it coming.

In Japan, a telescope at the Bisei Spaceguard Center (BSGC) came online in February. Its mirror is only 20 inches (a half meter) in diameter, but scientists plan to upgrade to a larger 40-inch (1-meter) diameter scope in September. And a couple months ago, the long-running Near-Earth Asteroid (NEA) Tracking project at NASA's Jet Propulsion Laboratory upgraded to a larger telescope that also makes monthly observations three times more often than before.

Syuzo Isobe of the Japan Spaceguard Association (JSA) described to SPACE.com the $7 million Bisei Center, operated by the JSA and funded by the Japanese Space and Technology Agency (STA).

"It will have two telescopes and six full-time staff," Isobe said. "The running cost this fiscal year is about $600,000. The center also would find space debris that could pose a hazard to Japan's STA's science satellites currently orbiting Earth."

Bisei Spaceguard Center in Japan. Credit: Syuzo Isobe

The Bisei Spaceguard Center's second telescope will have similar capabilities to the Lincoln Near-Earth Asteroid Research (LINEAR) asteroid-detecting telescopes in New Mexico.

LINEAR, which also uses two 1-meter telescopes, is by far the most successful asteroid search program to date. According to NASA, during 1999 LINEAR accounted for more than 70 percent of the discoveries of large asteroids.

Discovery of large asteroids by the major observatories Credit: NASA

LINEAR now faces tougher competition from Bisei, Spacewatch and NEAT (Near Earth Asteroid Tracking), which upgraded from a 1-meter telescope to a 4-foot (1.2-meter) telescope at the Maui Space Surveillance Site in Hawaii. (NEAT temporarily closed during 1999 and this boosted LINEAR's proportion of discoveries).

The entry of Japan into the search for killer rocks helps geographically, said Don Yeomans, manager of NASA's Near-Earth Asteroid (NEA) program office.

"The entry of the Japanese search effort is a very welcome one for a couple of reasons," Yeomans said. "It will add longitude diversity for the ongoing search efforts so that weather problems in the U.S. Southwest (where most U.S. search programs are based) will not be such a problem.

"Also, a discovery of a near-Earth object (NEO) [from] the [continental] U.S. or in Hawaii could be followed up easily by the Japanese site, which is several hours to the west," he said. "A very close, fast moving object can be quickly lost unless followed up immediately."

Follow-up observations are needed to track an asteroid over several days or weeks. They enable the orbit to be calculated. In 1998 a "potentially hazard asteroid" called 1998 OX-4 was detected by the Spacewatch team, but was lost due to the lack of follow-up observations.

Another benefit of a non-U.S. search team is "political diversity," Yeomans added. "NEOs are an international problem and they require an international solution. The more international partners that are involved, the less the entire effort need depend upon NASA-supported programs."

In his 1973 novel Rendezvous with Rama, Arthur C. Clarke describes a fictitious asteroid impact in Europe in 2077. This event forces Earthlings to create a "Spaceguard" system to detect and deflect Earth-threatening asteroids and comets. So far, most scientists and politicians, not to mention the public, have embraced such an approach.

For now, NASA has embraced the recommendations of the Spaceguard Report, named for Clarke's vision, and is aiming to find most of the large rocks.

The report identified asteroids 1 kilometer or larger as the main risk to civilization. The group acknowledged that comets and small asteroids also posed a threat but felt that less priority should be given these objects.

Spaceguard efforts have had ups and downs in other countries. Jin Zhu runs the Schmidt CCD Asteroid Program (SCAP) asteroid search project at Beijing Observatory in China. He told SPACE.com that the time allocated to asteroid detection at the observatory had reduced considerably during 1999.

In Australia Rob McNaught reports that he plans to have the 0.6-meter Uppsala telescope operational early in 2001. McNaught runs the only professional search program in the southern hemisphere and this is regarded as particularly important for follow-up observations.

The project is mostly funded under NASA's NEO Observations Program and is associated with the Catalina Sky Survey in Arizona. Between 1990 and 1996 McNaught was part of the "Spaceguard Australia" team looking for NEOs from the Anglo-Australian Observatory in Australia. That search effort found 30 percent of all new NEOs up to 1996, when the Australian government withdrew funding.

The news from Europe is not good. The OCA-DLR Asteroid Survey (ODAS) asteroid tracking project, located near Nice in France, stopped observing in April 1999 so it could be refurbished. Alain Maury, ODAS' technical project manager, told SPACE.com that, following management changes the telescope had closed down. "I am currently looking for a new job," Maury said. "I don't think the Schmidt telescope will reopen anytime soon."

Still, assuming that the latest systems can be configured to detect sufficiently faint objects, only one more dedicated telescope with a diameter of 1 meter or larger would be required to achieve the Spaceguard goal within a decade.

However, given the uncertainties with near-Earth asteroid search programs in recent years, perhaps it would be wise to have a few more telescopes spread around the world. Arthur C. Clarke may prefer to be known as a visionary rather than a prophet of doom.

Magnitude is essentially a measure of the faintness of an object. The higher the magnitude, the fainter the object. Magnitude 21, which is a typical upper limit for the above surveys, is exceedingly faint. Background light such as the Milky Way or moonlight will swamp any objects of this magnitude. A typical 1-kilometer asteroid would have a magnitude of 18 when observed about 100 million miles (160.9 million kilometers) from Earth, in the opposite direction to the sun. Spaceguard scientists need to detect these objects at larger distances and at less favorable angles, where they will appear fainter. Magnitude 20.5 has been suggested as an appropriate limit for reaching the Spaceguard goal of detecting 90 percent of these large asteroids within a decade.

All the above systems use CCD detectors for recording the images. These are similar to the devices used in camcorders to collect light digitally. To eliminate the effects of random bright spots in the images (mostly caused by cosmic rays) the usual procedure is to take between three and five shots of the same portion of sky. Sophisticated computer programs have been developed to scan the resulting images for signs of NEOs.