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On-orbit Satellite Collision
ElkGroveDan
post Feb 11 2009, 09:35 PM
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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/


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OWW
post Feb 11 2009, 09:58 PM
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Two satellites collide in orbit

Ouch. How long before LEO becomes a dangerous thick cloud of debris?
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nprev
post Feb 11 2009, 11:25 PM
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Holy crap!

Man, I knew it was getting crowded, but still amazed that it happened; the odds have to be pretty long. Article quoted Johnson from NASA as saying that there's no 'ATC' in space; maybe it's time to start thinking about establishing one.


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Guest_Zvezdichko_*
post Feb 12 2009, 09:12 AM
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This is bad. I hope it's not too late...
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ugordan
post Feb 12 2009, 09:25 AM
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What puzzles me is how come this collision wasn't seen coming. Usually the threatened satellite performs a collision avoidance maneuver.


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nprev
post Feb 12 2009, 10:59 AM
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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.


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rlorenz
post Feb 12 2009, 11:27 AM
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QUOTE (ElkGroveDan @ Feb 11 2009, 04:35 PM) *
Two satellites collide in orbit


Since this was a defunct satellite that hit the Iridium, it may not be quite the first
event of its type - a catalogued object (Ariane fragment) impacted the Cerise
microsatellite in 1996, severing the gravity gradient boom.
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nprev
post Feb 12 2009, 12:17 PM
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True, Ralph. I think that the 'first' here is the collision of two previously intact spacecraft, though. Seems as if the LEO environment is getting crowded enough to justify some sort of regulation in addition to intensified tracking efforts.

People have been saying this for years, of course, but it's probably time to do something about it, esp. considering the fact that there are an increasing number of nations and private concerns beginning to launch stuff in addition to the existing players. Somebody's billion-dollar baby is gonna get whacked at some point, and whoever it is will doubtless scream bloody murder; best course of action is to start formulating policies & procedures to mitigate the risk.


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Geert
post Feb 12 2009, 01:35 PM
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QUOTE (nprev @ Feb 12 2009, 05:59 PM) *
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.
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ugordan
post Feb 12 2009, 01:39 PM
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QUOTE (Geert @ Feb 12 2009, 02:35 PM) *
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.

QUOTE (Geert @ Feb 12 2009, 02:35 PM) *
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


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AndyG
post Feb 12 2009, 01:52 PM
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There's a trillion cubic kilometres of space in LEO, up to 2000km. Less than ten thousand objects above 10cm across.

A miss is as good as a mile in vacuum: I'm utterly stunned that this could occur. Paint flakes and the like, impacting in lower orbits, yes - but to quote Harry Hill...

"What are the chances of that happening?"
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dvandorn
post Feb 12 2009, 02:08 PM
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I don't know, it seems to me that, with the number of objects in orbit, this kind of thing was bound to happen sometime. I'm a little surprised that the event wasn't predicted, since there are several agencies across the globe that skin-track everything in orbit. (Where do you think those predictions come from that result in all those collision-avoidance maneuvers?)

-the other Doug


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algorimancer
post Feb 12 2009, 03:19 PM
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Yes, considering that they (apparently) routinely track fragments the size of bolts and coins (at least in LEO), I find this a tad suspicious. Just how "dead" was that Russian satellite? Not to be going off on a conspiracy rant or anything, just finding my belief a little strained here -- particularly in light of the recent Chinese and US ASAT operations.
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tasp
post Feb 12 2009, 03:40 PM
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Not to make light of this occurrence, but tracking of the resulting debris' orbital evolution could be interesting and relevant to several phenomena in the solar system. Laplace might find this to be a fascinating (serendipituous) experiment . . .





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ngunn
post Feb 12 2009, 04:35 PM
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QUOTE (tasp @ Feb 12 2009, 03:40 PM) *
fascinating (serendipituous) experiment . . .


And now at last the truth about that equatorial ridge - it's the remains of all the satellites the Iapetan's had in orbit before the first accidental collision started the Laplace cascade.
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