A few solar observation satellites have been launched in retrograde orbits [it requires a lot of energy]. Normally, a polar orbit satellite colliding with a low inclination one is the closest you get to a 'head-on' collision.

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What brings us together is stronger than what pulls us apart

According to BBC, about six thousand sats put in orbit...and as reliable as your source, Josh! Don't know about ones in decaying orbits

1. http://news.bbc.co.uk/1/hi/sci/tech/7885051.stm ....about these two colliding, and
2. http://news.bbc.co.uk/1/hi/sci/tech/7885750.stm ....about the general threat in space

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If you want to make an apple pie from scratch, you must first create the universe. CARL SAGAN

Mak: Pass the pepperoni please.
Fazor: "Hail, Bautainia! We pledge our hearts to thee! Science and woo, some babbling too, and astron-oh-meee!"
slang: And it made ash out of yew and tree.
Nicolas: ......you get somebody to yell "two engines, moron" at you... :D

I missed this post earlier (I was posting at the same time).

Thanks, NEO & Argos. I'm smarter now.

<I>A few solar observation satellites have been launched in retrograde orbits [it requires a lot of energy]. Normally, a polar orbit satellite colliding with a low inclination one is the closest you get to a 'head-on' collision.</i>

Not necessarily. Consider the case of a satellite constellation like Iridium where there are six planes of satellites, all with the same inclination but different RAAN (right ascention of ascending node) values (30 degrees between each plane). The difference between plane 1 and plane 6 is 150 degrees. That's not quite head on but close. Now, suppose another satellite was in an orbit with a RAAN 180 degrees out from one of the Iridium planes. In theory, they could hit head on.

Point taken.

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What brings us together is stronger than what pulls us apart

That's a good link - the drawing showing the six orbits makes the Iridium setup clear. I see they have a spare in each orbit.

I wonder if several more collisions happen as a result of this one, the chances for a runaway stream of collisions.

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"Toward no crimes have men shown themselves so cold- bloodedly cruel as in punishing differences of belief." - James Russell Lowell

Yep; not a safe place to let your kids play any more...

Might have to start designing on-board radar avoidance mechanisms for satellites., but at these speeds I don't know how that is possible.
..

On some of our dredge vessels, we mount turtle deflectors. (all those who laugh now, the Aussies are the ones to blame). Why don't we just put a high-speed variant of a turtle deflector on satellites? The principle is identical, the only design parameter that changes is the difference in relative velocity between a dredge vessel vs a sleeping turtle on one hand, and 2 satellites in earth orbit on the other hand. Easy.

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To the regular visitor of internet bulletin boards it is clear that it's an excellent idea your parents get to choose your real name.

I just found a website today that gives what I believe are reliable numbers. There are 3,323 payloads on orbit and 2,781 decayed* for a total of 6,104.

http://celestrak.com/satcat/boxscore.asp

*I don't know if there is a difference between decayed and the "decaying" you mention above, mahesh.

Nasa alert as Russian and US satellites crash in space:

Dysfunctional satellites? Do they come from broken homes?

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"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

I'm still wondering about the last line.
"Several times"? I know of one, were there others?

"Shot out of the sky"? Into where?
"Prevent them crashing to Earth"? I thought the idea was to intentionally crash them to the Earth quicker.

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haha...good idea ..we could call it the Cosmos deflector. In America we have "cow catchers" on the front of our trains....We could design a "Cosmos catcher" and have a compettition with the Aussies.....

The problem is these are very fast 'turtles' ; this collision took place at a relative speed of about 15,000 mph. The other design problem with the 'cow catcher' method is knowing from which direction the incoming IS COMING. Apparently these 2 collided at about a 90 degree angle to their trajectories.....

Nevertheless, I still think we should challenge the Aussies engineers with live real time tests....Aussie "turtle deflectors" vs. American "cow catchers"...slamming each others satellites and placing bets on E-bay on which one survives. Kidda like real time Space-bot competition.


BTW; Here's a You Tube video of the trajectories.. http://www.youtube.com/watch?v=_o7EKlqCE20

and debris trajectories from AGI.... http://www.agi.com/images/redlaf/cor...eakUp_3hrs.jpg


G^2

Has it occurred to anyone that this might not be an accident? It happened over Siberia. . . .

Yes, Warren; I was just about to add that to my last post...that this "accident" and is sure to open up a whole new world of "plausable deniability" among nations.

Next month ...US to Russia:
"Oh, your spy satellite had a crash, too?...well, hope you had insurance ....you really can't be too safe these days with all that space junk flying around out there".

well, if they predicted it we could have watched the impact or even filmed it. not much else you could do, but at least we could have learned something.

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"I will do my best to understand and explain the universe from big to small without invoking miracles, unrepeatable events, or divine intervention. In place of those things I will use observations, mathematics, and science."


-Cross
My travel blog

Some of my Astrophotography


Those that lack education have a hard time understanding its value. - Cross

Iridium satellites are hardly worth destroying. Maybe you're suggesting we did it on purpose? The Russian satellite wasn't even functional.

__________________
"I will do my best to understand and explain the universe from big to small without invoking miracles, unrepeatable events, or divine intervention. In place of those things I will use observations, mathematics, and science."


-Cross
My travel blog

Some of my Astrophotography


Those that lack education have a hard time understanding its value. - Cross

The Russians could easily have motive. China flexed their muscle, the the USA did the same thing. Thus, it's conceivable that the Russians wanted to get in on the act as well. The attack (if it was an attack) demonstrated an important assymetric antisatellite capability that the Russians possess. That is, they have so many satellites in orbit, they don't really need a sophisticated surface-to-space capability: all they have to do is steer a bunch of their satellites into other satellites. Do this a few times, and you get the chain reaction going, and you can deny the use of space to everyone. Since the US and NATO rely on space more than they do, it would hurt us more than it would hurt them if the cockadoodie ever really hit the fan.

As for evidence, I think there is circumstantial evidence that the collision was intentional. You say the Russian satellite was "defunct"; but there are levels of defunctedness. Do we really know for sure that the satellite was utterly incapable of receiving any sort of radio communications or any sort of maneuverability? Or had they simply stopped using it because they ran out of money or had something better to use? Can we reasonably expect the Russian military to be entirely truthful with respect to such knowledge?

For that matter, even if the Russian weren't behind the collision, we can't be sure that some group of hackers in Shenzhou or Berkeley didn't do it.

Consider the following from New Scientist:

Using a collision prediction program to perform a retroactive analysis of the satellites' orbits, aerospace analyst T.S. Kelso found that the Pentagon's public data showed that the two satellites would have missed each other by 584 metres.

But he says the uncertainty in that distance could be several kilometres. "There's no reason looking at the data that was available [to think the Russian satellite] was an immediate threat," says Kelso, who has been working with Iridium to assess the risk that the debris could collide with other satellites in the firm's fleet (see image above right).

Could Iridium have predicted a collision?

. . .

Iridium was receiving an average of 400 reports per week of objects coming within 5 km of one of their satellites. The reports were issued by the US Strategic Command's Joint Space Operations Center. "The ability actually to do anything with all the information is pretty limited," he said at the time, putting the risk of a collision from the close approaches at "about 1 in 50 million."

But an Iridium spokesperson told Reuters that the company did not get a warning before Tuesday's collision: "If the organisations that monitor space had that information available, we are confident they would have shared it with us."

In other words, they shouldn't have collided. Unless the rocket scientists were totally off base with their 1 in 50 million risk estimate. (Surely, that can't be the case! )

And like I said above, it also happened over Russia itself, where the event could be easily observed by the Russians themselves.

you need to take this to another forum. I think Conspiracy theories would be more appropriate.

__________________
"I will do my best to understand and explain the universe from big to small without invoking miracles, unrepeatable events, or divine intervention. In place of those things I will use observations, mathematics, and science."


-Cross
My travel blog

Some of my Astrophotography


Those that lack education have a hard time understanding its value. - Cross

Um.... I agree with Crosscountry.... this is not the place to speculate about a conspiracy... there is no evidence for it, and it is not the simplest explanation.

This event is very interesting and may have implications for future processes and policies... lets keep this thread on track.

I don't think this is something that can be derisively dismissed as a 'conspiracy theory'.

You cannot apply Occam's Razor, because the probability of an accidental collision on this scale is so remote that the currently popular explanation is at least as incredible as shadowy government agencies engaging in clandestine space warfare.

Of course that doesn't mean abandoning evidence and grasping at straws; what would likely settle the matter is the status of Kosmos 2251 before the collision; how 'dead' was it - just because it was no longer operating as a military communications satellite doesn't mean it had no fuel, power or communications capability.

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The idea that this was a deliberate act is unlikely in the extreme. The old Russian satellite died well over 10 years ago. Since it was dead, there was no way it could be controlled, so how could it possibly be blamed for causing the collision? As for hacking into Iridium, the idea might be possible in theory but unlikely. Command links are routinely encrypted to prevent such things.

Second, if you go to Heavens-Above.com and click on the top view link of the collision, you'll see that this was a near-broadside impact. The Russian satellite was inclinded about 70 degrees and the Iridium 86 degrees, so the relative angles of the velocity vectors is about 106 degrees. In terms of timing, this would require millisecond accuracy to cause an impact. Had either satellite arrived at the impact location even a millisecond early or late, they would've missed each other by several meters. That's a level of accuracy that's extremely hard to achieve.

In terms of producing debris, this impact was about as bad as you can get. The energy involved was amazing. It might take weeks or even months to catalog all of the pieces just as it did with that Chinese ASAT test two years ago.

Is this story connected with the stuff seen
falling in Texas yesterday?

Not according to US Strategic Command.

Early speculation was that it might have been debris from two satellites -- one American, one Russian -- that rammed into each other in space a week ago.

But the U.S. Strategic Command, which tracks satellite debris, said it was not. "There is no correlation between those reports and any of that debris from the collision," command spokeswoman Maj. Regina Winchester told CNN Monday.

So what was it? "I don't know," she responded. "It's possible it was some kind of natural phenomenon, maybe a meteor."

Meteor fireballs bright enough to be seen in the daytime are rare but not unheard of. Two of the most recent fell in October in the Alice Springs region of Australia and last June just west of Salt Lake City, Utah.

Well, the BA doesn't think so.

http://blogs.discovermagazine.com/badastronomy/2009/02/16/texas-fireball-update-the-video/


--Dennis

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Your theory is crazy, but it's not crazy enough to be true. -- Niels Bohr --

Ipsa scientia potestas est. ~ Knowledge itself is power.---- Bacon
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Ad eundum quo nemo ante iit.


Hint: this is at heart a scientific forum, and underneath the fooling around there are some diamond-hard minds hanging about, ready to tear you to shreads. -- mike alexander --

I think Occam would argue for an accident over a Russian plot. Heck they can't hit Mars half the time and that's a lot bigger target.

I wonder if any video exists of the controllers on watch in Strategic Command when this happened. I bet they wet their pants.

Just caught something on the news about a
meteor as big as a van. Looking forward to
the finders photos.

Don't count on it. I'll bet had had way more important things to do than wetting their pants.

__________________
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Your theory is crazy, but it's not crazy enough to be true. -- Niels Bohr --

Ipsa scientia potestas est. ~ Knowledge itself is power.---- Bacon
--------
Ad eundum quo nemo ante iit.


Hint: this is at heart a scientific forum, and underneath the fooling around there are some diamond-hard minds hanging about, ready to tear you to shreads. -- mike alexander --

I wonder if any video exists of the controllers on watch in Strategic Command when this happened. I bet they wet their pants.

This was their first satellite collision but it isn't their first breakup. Judging from the graphic I linked above, the collision happened outside of Space Surveillance Network (SSN) sensor coverage. Odds are some of the pieces were seen by different sensors at different times. Some of them might've been first detected by the Cobra Dane (my old stomping grounds), others by Clear, some by PARCS, all by the Air Force Fence, and some by Eglin. Each sensor site would see a bunch of uncorrelated targets (space objects that don't automatically correlate to a known satellite) and handling them is part of the job. As time passes, the pieces spread out so more debris can be detected as unique objects instead of a blob. It takes time to add each of the objects to the satellite catalog. The orbital analysts have to be able to uniquely and repeatedly identify each detectable piece. That can take weeks to months to complete. It's a pain.

That's right, but there was another station just looking in the right direction.