SAN FRANCISCO — Every driver has occasionally heard the sharp thwack of a pebble bouncing off the car's windshield. But what is merely startling on the highway can be catastrophic in space, where clouds of debris — orbiting the Earth at thousands of miles per hour — have the momentum to destroy military and civilian communications satellites.

The danger posed by orbital debris was recently brought to the fore by the collision of a 1,980-pound decommissioned Russian military satellite and a 1,500-pound spacecraft belonging to the Iridium satellite phone network. The Feb. 10 crash — the first head-on debris collision in space — highlighted the absence of any effective governmental or corporate solutions to a problem that can only worsen as more nations and corporations venture into space.

The incident took place at an altitude of about 490 miles, in the heart of what is called Low Earth Orbit (LEO). This zone — which stretches from 100 to 1,000 miles above the surface — is ideal for satellite communications because its relative proximity to Earth shortens the amount of time it takes for signals to bounce from place to place. As a result, LEO has become increasingly crowded, and now contains more than 400 military and civilian satellites.

This week, in fact, a piece of debris forced the crew of the international space station to take shelter in its escape capsule, a rare close call for the orbiting platform.

In 1978, NASA scientist Donald J. Kessler theorized that each accident in LEO would create a cloud of space shrapnel, imperiling other satellites in a cascade effect now known as the Kessler Syndrome.

The Space Surveillance Network, part of the U.S. Strategic Command, is already tracking more than 18,000 pieces of space junk — from whole satellites, such as the Russian Cosmos craft, to fragments the size of a softball.

Shortly after the February collision, U.S. officials said they were “tracking 505 pieces from the Cosmos satellite and 194 pieces from the Iridium satellite in two separate debris clouds.” A senior Russian military space official reportedly said the crash sent new debris radiating out in orbits from 300 to 800 miles.

 Coincidentally, the collision occurred while the United Nations Committee on the Peaceful Uses of Outer Space was convening a technical meeting in Vienna. The Committee, formed after the launch of Sputnik, maintains a voluntary registry where space-faring nations can choose to reveal the basic orbital parameters of their satellites.

But the international body has no authority to create or regulate space lanes, much less the means to track or clear debris already in orbit. The meeting served mainly to give non-governmental organizations a platform to argue for some plan to bring order to the orbits.

“This collision underscores in a dramatic way the importance of instituting an international civil space situational awareness system as soon as possible,” said Ray Williamson, the executive director of the Secure World Foundation in Colorado.

Modest progress is being made. France has pushed for the creation of a satellite tracking system, and the European Union recently allocated 50 million euros (about $63 million).

But so far there hasn't been a clear effort to create a worldwide space traffic control system.

Meanwhile, a private sector effort called SOCRATES — operating under the auspices of the Colorado-based software firm AGI — already downloads and analyzes publicly available data on objects in orbit and issues twice-daily reports on potential collisions. But SOCRATES didn't foresee the recent collision: Nicholas Johnson, an orbital debris expert for NASA, told reporters that the Cosmos-Iridium crash did not make the warning list on the day of the collision.

Iridium said it would use a spare satellite already in orbit to replace the destroyed spacecraft, and its communications network suffered little disruption in service.

And shortly after the collision, NASA officials told reporters that the added debris posed little risk to the International Space Station, which orbits 220 miles above Earth, well below the 490-mile-high crash.

The station, which is maneuverable, has swerved eight times to avoid debris in more than 60,000 orbits. Let's hope it doesn't take a sharp and deadly crack on the space station's windows to take orbital debris seriously. As John Logsdon, chairman of aerospace history at the U.S. National Air and Space Museum, said at a conference after the crash: “Do we have to kill people to pay attention?”

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