The Russian satellite was a Cosmos telecoms bird launched in 1993 and no longer in service. The other sat dated from 1997 and was an active part of the Iridium network, which was originally intended to be the world's first global mobile phone system.
Iridium Holdings LLC has a system of 65 active satellites that relay calls from portable phones that are about twice the size of a regular mobile phone. It has more than 300,000 subscribers. The U.S. Department of Defense is one of its largest customers.
Iridium does have advantages over other satcomms systems, however, as it requires only a small antenna rather than a dish or other directional apparatus. It is critical to many specialist applications today - many of them involving the military and intelligence communities, perhaps giving a clue as to why the US government was so keen to revive the system.
The Iridium Satellite corporation told AFP that it expected only minor outages as a result of the collision.
"This satellite loss may result in very limited service disruption in the form of brief, occasional outages," the firm said, adding that the company expects to have a network solution in place by Friday, and will move one of its in-orbit spares to permanently replace the destroyed satellite within 30 days.
NASA officials said that the ISS was not thought to be in significant danger as it orbits at an altitude of 220 miles, well below that of the satellite wreckage clouds. Should any debris threaten the space station, it has the ability to manoeuvre so as to avoid being struck: this has already happened on eight occasions.
The collision reportedly took place at 1655 GMT on Tuesday, at an altitude of 490 miles above Siberia.
Around 6000 satellites have been launched since 1957.
