Study Cites Hazards of Space Junk

The main orbit for the world’s communications satellites--about 22,000 miles out in space--could become hazardous and unusable unless old, worn-out spacecraft are discarded into an orbiting junkyard deeper in space, a study suggests.

Orbiting spacecraft debris already presents a hazard in low Earth orbit, say experts, noting that the International Space Station was maneuvered Wednesday to avoid a potential collision.

Richard Crowther, a British expert on orbiting space debris, said the world could face an even more serious problem if spacecraft operators don’t clean up after themselves in geosynchronous orbit, the high station used by most international communications satellites.

Without action, said Crowther, “crowding will occur and collisions will be inevitable.”

Satellites that download television signals to dishes on the ground are stationed about 22,300 miles above the equator, an orbit that allows a satellite to remain in the same place in the sky relative to a fixed point on the ground. That’s why it is called a geosynchronous orbit. Communication dishes aimed at such satellites can remain stationary, pointing to the same place in the sky.

“Geo-sync is a unique global resource,” Crowther said. “There is no place to move to once you have polluted this region.”

If satellites in geo-sync are simply left where they are after they wear out, they could remain there for thousands of years. The biggest risk is that their batteries or fuel tanks would explode, creating a cloud of small particles, each of which could be lethal for other satellites.

“A small coin traveling at 10 kilometers a second [about 22,300 miles per hour] through space will have the same impact energy as a small bus traveling at 100 kilometers an hour [62 mph] on the ground,” Crowther said in Science.

The International Telecommunications Union, which allocates positions in geo-sync, recommended years ago that satellite operators send their worn-out spacecraft to a higher orbit where they will not present a risk to other satellites.

Not enough satellite owners are following the rules, said Nicholas L. Johnson, chief scientist and manager for the orbital debris program office at NASA’s Johnson Space Center in Houston.