They may be tiny, but at estimated speeds of 38,000 kilometers per hour size doesn't exactly matter.

Space debris, the refuse of exploded satellites, has been a major concern for international scientists and space flight officials sending manned spacecraft into orbit for years. Roughly 10,000 man-made objects are floating in orbit, according to NASA, only 5 percent of those being useable spacecraft.

The danger that those objects pose to other spacecraft has been confirmed on several occasions in recent years. NASA is still not ruling out the possibility that the Columbia space shuttle was damaged in-flight by some space debris, leading to its eventual disintegration as it re-entered the earth's atmosphere on Feb. 1, 2003. Seven astronauts died in the explosion.

"It is a real threat," said Dr. Frank Schäfer, a researcher at the Fraunhofer and Ernst Mach Institute in southern Germany. "(We are) constantly improving the individual subsystems and components of the shuttle to make it more impact resistant."

A shield against trouble

Three years ago, Schäfer and a design team finished a protective shield that will cover the European Space Agency's Columbus Laboratory, which will be attached to the International Space Station. The shield consists of a multi-layered protection "bumper" that would break up the particles as they hit, lessening the damage caused to the actual outer wall of the Columbus Laboratory.

Earthly materials such as Kevlar and a ceramic fiber created by Nextel are being used to dull the impact of the particles, most of which are no bigger than 3 mm. Rather than just Kevlar fabric, which adorns most other spacecraft, Schäfer and his team crafted Kevlar plates about 6 mm thick.

"In the Columbus shield, you have to shield large debris masses," he said. "You need added protection, and added layers. That's the recipe to produce a good shield and that's what we did."

Special danger for European lab

Technicians in the Astrium, in the port city of Bremen, are currently building the shield. The entire shield has been split into 80 plates measuring approximately one meter by one meter. Each plate is currently being attached to the laboratory, which is scheduled to be shot into orbit in either 2004 or 2005.

Inside, scientists will be able to conduct research on one of 12 research stations. The lab will attach onto the front of the space station.

"The positioning of Columbus, when it is completed, is different to that of the U.S. or Russian parts (of the station)," said Matthias Hill, of the Astrium in Bremen. "It will be the nose of the ISS and come into more contact with space debris and face more danger."

For larger pieces of space debris, the ISS astronauts will have to rely on the SSN's sensors to alert them.

The network keeps a watch on larger-sized space debris, allowing flight engineers to move spacecraft out of harm's way. In a close call last November, the network was able to alert the International Space Station before bits of an exploded Russian satellite passed by too closely. By firing one jet, the space station moved itself further away from the pieces of the exploded satellite.

U.N. seeks agreement

"There is still a real risk that a collision could cripple the shuttle or threaten the safety of the crew," Frederick Hauck, president and chief executive officer of AXA Space, following the release of a 1997 report on space debris.

The European Union reached a similar conclusion following a 1997 conference and the concern hasn't lessened since then. This week, scientists and officials from the United Nations Office for Outer Space Affairs are meeting in Vienna to set out international guidelines for reducing the amount of space debris. Among the proposals: putting satellites out of orbit, where they can break up without damaging other satellites or manned spacecraft.