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Friday, 25 May, 2001, 11:09 GMT 12:09 UK
Space debris warning
Swarms of objects circle the Earth, all man-made
By BBC News Online science editor Dr David Whitehouse

According to two private researchers more action needs to be taken to reduce space pollution by old satellites and rockets.

If nothing is done, they say, certain orbits, especially those used by manned spacecraft, could become more dangerous and remain so for hundreds of years.

Despite this dire warning, space agencies say that, while in the past they may have been responsible for a growing amount of space junk, they now have policies to minimise the hazard.

It is estimated that there are nearly 10,000 man-made objects larger that 10 cm (4 inches) in orbit and probably tens of millions of fragments less than 1 cm (0.4 inch).

Deliberate destruction

Space debris facts
Radar studies indicate that there are10,000 objects larger than 10 cm
100,000 objects between 1 and 10 cm
Tens of millions smaller than 1 cm
Donald Kessler, a private consultant, and Phillip Anz-Meador of Viking Science and Technology in Houston, US, gave their warning at a recent conference in Germany.

The researchers studied the deliberate destruction of a US military spacecraft in 1985.

In September of that year the P-78 satellite, weighing 850 kg (1874 pounds), was intentionaly struck by a 16 kg (35 pounds) projectile. From the collision 285 fragments were catalogued.

The researchers say that by studying the history of these fragments they can obtain a broad picture about how long space debris would remain in orbit.

Over the following years most of P-78's pieces burnt up in the Earth's atmosphere and by January 1998 only eight fragments remained in space.

'Too hazardous'

From this data the authors of the report conclude that even if nothing is done to reduce the number of satellites in orbit, there is the possibility that they could contribute to a growing cloud of space debris in certain orbits.

They say: "...the fragment population would become too hazardous to continue space operations in low Earth orbit."

Small objects regularly strike satellites and manned spacecraft but so far no manned mission has been seriously affected.

In its 14 years in space the Mir space station did not have its work hindered by space debris, even though its exterior was pitted with minute holes from collisions.

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