On-orbit Satellite Collision Options

[ElkGroveDan]

Two satellites collide in orbit
BY WILLIAM HARWOOD

Posted: February 11, 2009

In an unprecedented space collision, a commercial Iridium communications satellite and a presumably defunct Russian Cosmos satellite ran into each other Tuesday above northern Siberia, creating a cloud of wreckage, officials said today.

Iridium satellite
An artist's concept of an Iridium satellite orbiting the Earth. Photo: Iridium

The international space station does not appear to be threatened by the debris, they said, but it's not yet clear whether it poses a risk to any other military or civilian satellites.

"They collided at an altitude of 790 kilometers (491 miles) over northern Siberia Tuesday about noon Washington time," said Nicholas Johnson, NASA's chief scientist for orbital debris at the Johnson Space Center in Houston. "The U.S. space surveillance network detected a large number of debris from both objects."

MORE.....


http://spaceflightnow.com/news/n0902/11iridium/

[nprev]

I wondered that too, G. The Cosmos seemed to be dead already, but the Iridium's condition wasn't stated. All I can think is that the Russians weren't keeping tabs on the Cosmos anymore, and maybe the Iridium wasn't being tracked because it's a private spacecraft...?

There's obviously some sort of disconnect here, but not sure what it is.

EDIT: It seems that the Iridium was in fact still active, so this remains puzzling.

[Geert]

EDIT: It seems that the Iridium was in fact still active, so this remains puzzling.

Do the Iridium satellites have own maneuvering engines? The space shuttle and ISS have several times dodged potential close encounter situations, but other craft simply do not have the capacity for this (Hubble for instance...).

What surprises me is that this happened at 800 km, as far as I know there is a lot more traffic further down (ISS altitude) and/or higher up (stationary orbits). Also, what kind of orbit was the other satellite in, in other words how fast did they hit?

Worst case is a kind of chain-reaction, this has resulted in a large cloud of debris, which will slowly spiral down through all the other crowded orbits below, and it might hit other satellites in turn. Big satellites like Hubble, which can't steer themselves out of the way, are the most vulnerable, hope it stays clear!

Regards,

Geert.

[ugordan]

Do the Iridium satellites have own maneuvering engines?

I believe so, given that one of the 8 "spare" satellites will now be moved into Iridium 33's position.

Also, what kind of orbit was the other satellite in, in other words how fast did they hit?

Roughly polar orbits. They hit at almost a 90 degree angle and that comes out to something like 11 km/s relative velocity. Ouch.

http://spaceweather.com/swpod2009/12feb09/deak1.gif

[Geert]

They hit at almost a 90 degree angle and that comes out to something like 11 km/s relative velocity. Ouch.

http://spaceweather.com/swpod2009/12feb09/deak1.gif

That picture says it all, the more you think about it the more perplexed you are that this could happen, such a tremendously small chance...

Two satellites, each over 1 ton in weight, hitting at 11 km/sec, must have been quite some fireworks in the Siberian sky, some of the fragments might even have made it into solar orbit... Shape and progression of this debris cloud will indeed be an interesting mathematical experiment...

Regards,

Geert.