The crash, which took place on Tuesday above Russia's Arctic north, involved a spacecraft of Iridium Satellite LLC and a Russian communications satellite, said Air Force Colonel Les Kodlick of the US Strategic Command.
"We believe it's the first time that two satellites have collided in orbit," he said, calling the debris potentially a problem that could require more debris-avoidance maneuvers among space-faring nations.
The crash occurred at roughly 485 miles (780 km), Kodlick said, an altitude used by satellites that monitor weather, relay communications and perform scientific observations.
"It's a very important orbit for a lot of satellites" and highlighted a need for improved awareness of events taking place in space, Kodlick said.
The command's Joint Space Operations Center is tracking 500 to 600 new bits of debris, some as small as 4 inches (10 cm) across, in addition to the 18,000 or so other man-made objects it previously catalogued in space, Kodlick said.
CONSTELLATION STILL OPERATING
Bethesda, Maryland-based Iridium operates the world's largest commercial satellite constellation made up of some 66 cross-linked satellites plus orbiting spares. It provides voice and data services for areas not served by ground-based communications networks.
The operation remained healthy, though some customers may experience brief outages pending a temporary fix expected to be in place by Friday, said Liz DeCastro, an Iridium spokeswoman.
She said Iridium planned to move one of its in-orbit spare satellites into the constellation to replace the lost craft within 30 days.
"This event is not the result of a failure on the part of Iridium or its technology," DeCastro added in a statement.
Iridium's craft, shaped like a box with wings and weighing about 1,300 pounds (600 kg), was launched in September 1997 aboard a Russian rocket, said Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics and space program historian.
The Russian craft, a barrel-shaped cylinder with a mass of 1,800 to 1,900 pounds (800 to 850 kg) known as Cosmos 2251, was launched in June 1993 and probably stopped working five to 10 years ago, he said.
The collision occurred in a polar orbit not far from that of a defunct Chinese weather satellite shot apart by a ground-based ballistic missile in a Chinese weapons test in January 2007. The United States used a missile from a Navy warship to blow apart a tank of toxic fuel on a defective US spy satellite last February.
Among the 18,000-plus objects being tracked in space by the US Strategic Command are operational and defunct satellites, spent rocket boosters and debris.
Nicholas Johnson, an orbital expert at Nasa's Johnson Space Center in Houston, said it was uncertain how much new debris had been created by the crash.
"It takes a while for the debris to spread out and for us to get an accurate head count," he said. Nasa receives orbital tracking services from the Defense Department and regularly maneuvers its spacecraft to avoid debris.
The top priority is guarding the International Space Station, which orbits at about 220 miles (350 km), substantially below the collision.
DeCastro said Iridium, which contracts with Boeing Co to maintain and operate its satellites, received information about the crash from the US government.
There was no indication that the collision was intentional on the part of anyone, said a US government source who asked not to be named.