After hunting asteroids for two centuries, astronomers achieved a minor milestone earlier this month when the tally of known space rocks whose orbits are well established surpassed 30,000, three times the total less than 3 years ago.

There was no press release. The people who do the counting are too busy for ballyhoo.

And soon they will be busier. The tally is expected to double in a matter of months and likely soar a startling six-fold or more within 3 years. And these are just the well-studied rocks. Roughly 150,000 more have been spotted but need further study before their orbits can be known well enough to put them in the books.

Why the bounty? Telescopes are getting bigger and better, and the high-tech electronic cameras that record the observations are able to see things that were invisible just a few years ago.

Several leading asteroid researchers interviewed by SPACE.com warned of a looming bottleneck in the worldwide network of computers and researchers who determine the future paths of thousands of asteroids that are detected every month. One crucial link in the process depends mostly on amateur astronomers who help to put together painstaking details of an asteroid's path after it has been first spotted.

"The increasing number of new asteroids will eventually overwhelm observers who do the follow-up," said Benny Peiser, an expert on the threat of asteroids at Liverpool John Moores University in the United Kingdom.

The flood of data also could overload the computers and staff of the primary international clearinghouse for asteroid information, the Minor Planet Center in Cambridge, Massachusetts.

The global asteroid monitoring system is a sometimes-loose collaboration of private institutions and government agencies, along with the amateur astronomers and several dozen professional asteroid researchers around the globe.

The amateur component has developed rapidly over the past decade, often on an ad hoc basis.

The professional side of things is marked by frequent disagreement between its most fervent and productive asteroid hunters. They argue over how much information should be provided to the public and how quickly it should be released. They debate definitions, procedures, and the fine points of risk assessment.

But the scientists all agree on one thing: Earth will one day be targeted by a potentially devastating asteroid, and they aim to avert disaster by spotting it in advance.

The most worrisome rocks are the big ones: Asteroids larger than 1 kilometer (0.62 miles) across suspected of hitting Earth every 100,000 to 300,000 years, says Michael Paine, a volunteer with Planetary Society in Australia. Paine tracks the varying estimates of asteroid impact risks made by several research groups. A collision from an object this large would rock the planet, disrupt the global climate for years and could render some species extinct.

Asteroids 100 meters (328 feet) across or larger slam into the planet every 1,000 to 3,000 years, Paine says. Such an event could eliminate a city or create a tsunami that might inundate shore communities and even large cities along multiple coastlines.

If and when such a calamity is foreseen, precautions could include evacuating areas to avoid any local disaster that might be rendered by a small asteroid. In the future, a spacecraft might be sent to destroy or deflect a larger incoming object, saving the planet Hollywood style.

The first priority of business on everyone's list is to find more space rocks. Lately, this is not a problem, and the success of asteroid hunters grows more stunning by the month.

The first asteroid, Ceres, was discovered in 1801. It took nearly 200 years -- until 1999 -- for astronomers to find and number the next 9,999 cousins of Ceres. But with advances in telescope technology and additional human and optical resources devoted to the task, the count has tripled since then. On Oct. 2, it reached 30,716.

"I'm guessing we ought to be up to 200,000 in 2004," said Brian Marsden, who serves in a part-time capacity as director of the Minor Planet Center, "assuming we can physically keep up with it."

The center, which operates under the auspices of the International Astronomical Union, processes the world's asteroid observations and connects major observing programs to the individuals who do follow-up observations.

The center processes more than 70,000 observations on a busy day, Marsden said. The tremendous amount of data stems from this fact: Although a nearby asteroid can often be recognized from data on a single night, some must be observed over several months, even years, to determine their ultimate path or destination.

In September, a record 1,642 asteroids were officially numbered by the Minor Planet Center. But there are many more asteroids that have been spotted. In all, some 150,000 are already known. Most of these have not been observed well enough to determine their orbits precisely. Only when an asteroid's path is pinned down with certainty does it get an official number.

To keep up with the growing workload, Marsden and his two colleagues frequently put in 16-hour days and work six or seven days a week, he said.

Most asteroids pose no threat to Earth, traveling around the Sun between the orbits of Mars and Jupiter. But the gravity of Earth and other planets can cause an asteroid's path to change with each orbit. Of greatest concern are asteroids 1 kilometer or larger that stray close enough to our neck of the solar system that they could one day cross paths with the Earth.

Researchers disagree on how many of these Near Earth Asteroids there might be, but the leading estimates range from 700 to 1,200. Roughly 500 have been found, none of which poses a threat anytime in the next century.

But smaller objects are tougher to spot, and some are discovered just days before they pass by Earth.

On Oct. 8 of this year, for example, an asteroid thought to be between 50 and 100 meters in diameter zoomed by our planet at little more than twice the distance to the Moon -- a whisker by the standards of our solar system's size. The object was first detected just two days prior. Its path was determined only the day before the close encounter.

Search programs "red flag" such nearby objects, which move more quickly against the background of stars as compared to more distant asteroids. Scientists say it is critical to note these fast-movers and quickly do follow-up observations to make sure Earth is not in their sights.

That's where the amateurs come in.

Around 100 highly qualified but unpaid astronomers are often well equipped and are viewed as every bit as capable as professional astronomers. But there simply won't be enough of them as the ability of professionals to spot smaller asteroids improves and the data load grows.

"Sooner or later things are going to come to a crunch," Marsden says.