Talk:2009 satellite collision

Debris
I live in Kentucky, and for the last two days we have heard low, loud, and rumbling explosions every couple of hours over several counties. It is supposidly the debris re-entering the atmosphere.

Was wondering if anyone else had experienced this? Even makes you wonder what was on that satellite after two days...(66.156.138.35 (talk) 16:45, 14 February 2009 (UTC))
 * The news articles are as yet too speculative and new to include in the article, but reports of possible re-entering debris are cropping up. I spotted this on the Space.com news links on Yahoo news: Debris From Satellite Crash Possibly Fell Over Kentucky, Texas, Tariq Malik Senior Editor SPACE.com – Sun Feb 15, 5:45 pm ET. (This may be deleted once better information is in) Tomligon (talk) 03:39, 16 February 2009 (UTC)

NORAD was moments away from an emergency public broadcast in Canada re debris. I'm not sure why there is mention of 'radioactive' debris in this newspaper article either. Calgary is a major city (pop. 1 million) in the province of Alberta. http://www.calgaryherald.com/entertainment/Calgary+dodges+space+junk/1290211/story.html —Preceding unsigned comment added by 204.191.190.96 (talk) 05:20, 11 June 2009 (UTC)

Accidental?
Perhaps I'm reading this too literally, but nowhere in the article does it say that this was an accident. I assume it was, but it is entirely possible to read this article and assume that the satellites were forced to collide on purpose, without a reason given. Would it be agreeable to change it to include the words "accidental" or "unexpected?" —Preceding unsigned comment added by 216.54.22.188 (talk) 19:11, 12 February 2009 (UTC)


 * So... no one's willing to change it?


 * Oh, nevermind. Thank you.


 * I don't know. Actually, a case could be made that, if it was really an accident, then it is a very strange one. From the limited knowledge i have about orbital mechanics and how orbiting objects (both 'live' and dead, ie, retired satellites and debris) are handled, this collision should have been predicted with more than enough time to allow (at least) the Iridium to be raised into a slightly higher orbit temporarily. Could it be that the operators of the Iridium constellation had some incentive to purposefully damage one of their satellites? (For example, insurance coverage actually being more profitable than the working satellite itself; as far as i know, the Iridium is considered a constellation that far outgrew its potential market.) —Preceding unsigned comment added by 146.193.39.206 (talk) 20:01, 12 February 2009 (UTC)


 * True, but according to the wikipedia article on the Iridium network, the original owners are now bankrupt, so much of the original cost of the system is no longer a problem. Furthermore, it appears that a successor to the network is being planned, which seems to suggest that the current system is profitable enough for greater bandwidth to be required.

I don't know exactly how satellite tracking works, but it may be possible that since it was a defunct Russian satellite that it was only being tracked by Russia, not by NASA (i.e. cold war relic). As these satellites are in relatively low earth orbits, I don't know whether the cumulative effect of the atmosphere on the long lived Russian satellite may have caused this. Or alternatively it is possible (although it appears unlikely) that it was a deliberate attempt to test ways to knock other satellites out of orbit/ destroy them. —Preceding unsigned comment added by 86.131.102.102 (talk) 20:43, 12 February 2009 (UTC)


 * It is true that the original owners/builders of the Iridium satellite network went bankrupt. But economically, that would have no relevance to the argument of the second commenter (146.193.39.206) about the hypothetical possibility of an insurance policy payout potentially being of greater value than the return on investment of operating the sattelite by the present owner/operator of the Iridium network.  The present owner has an economic value (cost to acquire, maintain, etc. as well as revenue stream from having n satellites rather than n-1 satellites in orbit.  I am commenting only on the potential validity of the argument; not on the probability of this hypothetical being true. N2e (talk) 22:02, 12 February 2009 (UTC)


 * How is it not valid? If the Iridium network was largely redundant for its first owner, it might still be for the present owner. Presumably the present owner could not have bought just half the constellation (or perhaps he could, but since it was dirt cheap anyway, why not go for the whole thing). The point is, the current owner might have simply realized that he could comfortably do away with one or two satellites, and still make a very slim profit from a miscalculated insurance policy (of which examples abound). Note that, according to the news, the Iridium operators are apparently not having much trouble in replacing lost functionality using 'spare' satellites; perhaps they realized that their `spare capacity' is simply over-dimensioned. I'm not saying, of course, that this was some sort of planned event; but it leaves the impression that someone decided, well in advance, that it was OK.

BTW, i'm the same guy as the post from IP 146.193.39.206. —Preceding unsigned comment added by 89.152.245.176 (talk) 00:32, 13 February 2009 (UTC)


 * A few comments. ON the economic viability of Iridium.

There is a war on. As I understand it US and NATO/Coalition partners have been buying pretty much all the commercial satllite time they can get. I can't imagine that running those satellites in unprofitable at the moment - although Iguess the projected withdrawals from Iraq might make it so.

ON the subject of it the orbits could be predicted then why was the Iridum satellite not moved out of the way. Well may it had no maneuvering fuel left. Or maybe it had enough to move it away and not enough to put it back in a useul orbit. IN which case they are better of leaving it where it is an hoping for a miss.

Just a thought. (or two) 219.90.144.59 (talk) —Preceding undated comment was added at 13:26, 14 February 2009 (UTC).

"Well may it had no maneuvering fuel left." It does. Or at least Iridium claim they could have manoeuvred it.Nasa, whilst they tracked both objects, predicted them to miss each other by a large margin (were talking tens/hundreds of kilometres- i can't remember the exact value). For the record, the cost to maintain one less satellite is effectively zero, since they still have to track the other 71 or so and use them. Your point about the gain from the insurance is valid. I thought the implication was that the company weren't making money, and that a collision with one of there satellites was a way to recoup losses. 86.174.122.122 (talk) 23:45, 14 February 2009 (UTC)

The USSSN is of course tracking *all* objects it can detect, no matter who launched a particular object. For the reason why no evasive actions were taken, it might probably be that starting evasive maneuvers for every possible close encounter in LEO is simply not feasible: "At the time, Campbell said that Iridium was receiving an average of 400 reports per week of objects coming within 5 km of one of their satellites." and "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." --Cruncher (talk) 04:42, 19 February 2009 (UTC)

presumably this 584 metre prediction is attributable to the Intel Pentium floating point bug? 75.87.134.179 (talk) 19:00, 20 July 2009 (UTC)
 * Why would you assume that? 87.110.133.184 (talk) —Preceding undated comment added 00:54, 29 October 2010 (UTC).

Not really the first collision?
I started this article because the news said it was the first satellite collision, which I thought was noteworthy. If this is not the first such collision, then perhaps this isn't deserving of its own article. I will trust whatever a concensus of editors decides. Grundle2600 (talk) 02:23, 12 February 2009 (UTC)
 * It's still fairly notable. The other collisions were all low-velocity, so little debris was produced, and the spacecraft were still operable afterwards (although Mir sustained heavy damage). Also, they all occurred during rendezvous attempts. This is the first time the spacecraft have been in completely different orbits. -- G W … 02:29, 12 February 2009 (UTC)
 * OK. Thanks for explaining that. I agree with you. Yes, bumps during rendezvous attempts are a very different thing. Grundle2600 (talk) 02:33, 12 February 2009 (UTC)
 * Also see this, which clearly defines the notability: http://www.nytimes.com/2009/02/12/science/space/12satellite.html?ref=space 207.237.33.124 (talk) 05:37, 12 February 2009 (UTC)
 * Thank you for the link! Grundle2600 (talk) 12:53, 12 February 2009 (UTC)
 * FYI, this article is going to be on ITN very soon. I am just polishing it for the stage. --BorgQueen (talk) 13:07, 12 February 2009 (UTC)
 * Oh wow! Thanks! Grundle2600 (talk) 13:54, 12 February 2009 (UTC)

The "collisions" between DART and MUBLCOM and between Progress and Mir occured during deliberate attempts to bring two spacecrafts together slowly. So they were very different. The collision of Cerise, however, was quite similar. It too featured a functioning satellite colliding completely accidentally with space debris. The only difference is that in the 2009 event, the other object colliding was an old, "dead" satellite, so we have two real satellites colliding. In 1996 it was a satellite meeting a piece of debris that was not designed to be a functioning satellite. /129.142.71.166 (talk) 16:38, 12 February 2009 (UTC)
 * Thanks for explaining that. Grundle2600 (talk) 17:50, 12 February 2009 (UTC)

Ground track plots
For whoever is interested here are links to the ground track plots of both satellites at the time of collision, courtesy of Heavens-Above:

84user (talk) 15:23, 12 February 2009 (UTC)
 * Cosmos ground track plot
 * Iridium ground track plot


 * Ah, silly me, they already have better orbit tracks linked from the web site here:
 * top
 * side view
 * 84user (talk) 15:28, 12 February 2009 (UTC)

Damn, that's closer to a head-on collision than I would've imagined! Potatoswatter (talk) 21:34, 12 February 2009 (UTC)

Any legal/compensation consequences?
Are there likely to be any legal claims for compensation arising from this?

It seems like the Russian satellite was a derelict one, while the Iridum one was still operating. Had the russian orbit decayed from its' assigned path, or were they both still following their assigned orbital path? If one of them was off the assigned orbit, it seems like the other could claim damages against them. And probably for a large amount.

Or do such legal considerations even apply in space? What court would have jurisdiction to hear such a case? And what set of laws apply out there? Might be some precedents set here. T-bonham (talk) 17:21, 12 February 2009 (UTC)
 * That's up to the Siberian courts to decide - it happened in their jurisdiction. Grundle2600 (talk) 17:52, 12 February 2009 (UTC)


 * I would think that satellites are a "fly at your own risk" and the only compensation Iridum would get is if they have insurance on their satellites. There is a limit to a country’s jurisdiction before you enter space but different organizations place different upper bounds. Jojii (talk) 17:57, 12 February 2009 (UTC)


 * I was joking about the Siberian courts. Heh heh. Grundle2600 (talk) 19:47, 12 February 2009 (UTC)

"a recent spaceflight"?
Let the Recent Space Wars and Demolitions begin. --AaThinker (talk) 18:27, 12 February 2009 (UTC)

Weight of Russian satellite
According to the BBC the Russian satellite weighs 950kg (2,094lb). Not 900kg as stated. I haven't changed it, but can someone check which it is and correct it as appropriate

Link: http://news.bbc.co.uk/1/hi/sci/tech/7885051.stm?lss


 * So fixed. Btw, the BBC article has a nice graphic image. Can anyone make something similar? --BorgQueen (talk) 18:48, 12 February 2009 (UTC)

Gunther says 900 kg and I'd believe him over the numbers-challenged BBC. Also, it was presumably out of fuel and hence weighed less. Potatoswatter (talk) 21:30, 12 February 2009 (UTC)

Indeed. Apparently all the cosmos satellites weighed 900kg. I suggest we go with that figure. Although that figure doesn't include fuel usage, and more importantly, the Cosmos most likely wasn't out of fuel. 86.174.122.122 (talk) 23:49, 14 February 2009 (UTC)

Threats to lower orbit
The two satellites are said to have been travelling at almost perpendicular paths. This means that we can more or less add their velocities together to get the velocity of the debris. A satellite in a circular orbit (Iridium 33 had a nearly circular one) which gets one single boost, will settle into an elliptical orbit with the height of the original orbit as its lowest point. The danger to spacecraft and satellites should therefore be greater above the Iridium orbit than below. EverGreg (talk) 19:18, 12 February 2009 (UTC)


 * Don't drink and derive. Potatoswatter (talk) 06:30, 13 February 2009 (UTC)
 * ? :-) EverGreg (talk) 11:42, 13 February 2009 (UTC)
 * Oh well, this simulation shown at youtube predict two clouds of debris in perpendicular directions. :-/ EverGreg (talk) 13:14, 13 February 2009 (UTC)
 * Looks like the original source of that is http://www.agi.com/corporate/mediaCenter/news/iridium-cosmos/, which has multiple animations and graphics, in higher quality. I think this was worthy of an External Link, and made it so.  If anyone disagrees, discuss. TJRC (talk) 00:16, 14 February 2009 (UTC)

WTF?
How the hell could have this been permitted to happen? Stationkeeping, anyone? Even if the Kosmos was unmanoeuverable, certainly the Iridium could have been raised to a slightly higher orbit? Even if it took many orbits of advance notice, this isn't supposed to be a problem for tracking stations, right? They should be able to tell well in advance that this would happen. —Preceding unsigned comment added by 146.193.39.206 (talk) 19:40, 12 February 2009 (UTC)


 * They can greatly reduce the odds of a collision. But they can't reduce the odds all the way down to zero. Grundle2600 (talk) 20:51, 12 February 2009 (UTC)


 * They can. A robust tracking system is not necessarily meant to accurately pinpoint the exact position of every satellite through time; that would be real hard, and error-prone to some extent. What it should do is to maintain, for each satellite, a concept of an orbital corridor: A sort of tube that strictly contains the orbit of a satellite, even if the precise position of the satellite inside the tube is not known exactly. Then, as long as no two corridors intercept, there is zero chance of a collision. The parameters of each orbital corridor are updated by periodic readings of actual position obtained by the tracking station, with some safety margin added in. —Preceding unsigned comment added by 89.152.245.176 (talk • contribs)


 * Presumably the Iridium sat was in the orbit its operators wanted it to be in. If they made avoidance maneuvers every time some stray sat was expected to come close, how much would they shorten the station-keeping life of their bird?  They trade the risk of immediate destruction for a chance at longevity. (sdsds - talk) 23:06, 12 February 2009 (UTC)


 * Well, if you're not going to manoeuvre to stand clear of another satellite, then when are you going to do it? Your argument makes sense when applied to avoiding assorted debris, but whatever the importance scale that determines whether a satellite should be restationed, avoiding a collision with a bigger object with a predictable orbit (such as the Kosmos) must be on the very top. —Preceding unsigned comment added by 89.152.245.176 (talk • contribs)


 * You seem to be attributing to Iridium some sort of ignorant foolishness. It seems more likely they took a well-calculated chance, and lost their bet. One wonders what odds SOCRATES had given on the conjunction. And one wonders if Iridium 33 was insured, and if by collecting the insurance Iridium will be better off.... These both might give hints at Iridium decision not to maneuver. (sdsds - talk) 05:14, 13 February 2009 (UTC)

SOCRATESdid not have it's probability listed. Don't know if COMBO did? Problem is TLE's have such large errors in them as state vectors even the computed probabilities at celestrak are really not very accurate. --aajacksoniv 19:42, 19 February 2009 (UTC)


 * No, i'm not. Quite the contrary: I'm saying that there is absolutely no chance that they wouldn't know this was going to happen, and with more than enough time to make something about it. What i'm questioning is their apparent willingness to just let it crash. You talk about making a bet and losing it: Sure, but it is a very poor bet. Any decent tracking system would class the upcoming encounter as an extremely high probability impact; there is simply no way around it. Afterall, these are fairly large objects, not just random space junk, and they have completely predictable orbits, at least for a span of a few days (and i'm being conservative here). So if you're going to make a bet such as this, it can only be because you don't value your equipment that much. That is precisely my point. Iridium must have judged it would stand to lose nothing (or even gain) by allowing this to happen. Any operator which has any significant investment in its satellites would have restationed in this particular case, even if it meant completely exhausting manoeuvering fuel.89.152.243.222 (talk) 13:39, 13 February 2009 (UTC)


 * Are there enough tracking records to tell whether Iridium 33 executed any suspicious "stationkeeping"? For satellites at different altitudes, it seems a bit of a longshot to make them collide in one try. My bet is that Iridium laid off the navigators to save money, or that 33 was almost out of fuel and they simply bet nothing would happen. Potatoswatter (talk) 06:36, 13 February 2009 (UTC)


 * The only 'non-nasty' explanation i can think of is that Iridium 33 was actually already out of manoeuvering fuel (but otherwise operational) and that the owners of the constellation did not want that to be known, presumably to avoid having their assets regarded as unmantainable hardware. Perhaps most of the Iridium satellites (at least the older ones) have already almost lost their stationkeeping ability, and this unfortunate event just happened to be unavoidable.89.152.243.222 (talk) 13:39, 13 February 2009 (UTC)

Globalstar hypothetical
Suppose you were responsible for GLOBALSTAR M045. Would you maneuver to avoid the conjunction with COSMOS 2253 coming up on 2009 Feb 18? There are 3 chances in 1000 of a collision.... What percent of the sat's fuel would you be willing to burn to decrease that probability to 3 chances in 10,000? SThis article would be better if it somehow clued readers in to the idea that Iridium may have faced a decision just like that.... (sdsds - talk) 15:35, 13 February 2009 (UTC)


 * I doubt that the excepted collision chance for the Iridium was as low as 3/1000... But referring to your example, yes i would reposition M045. And if i somehow would be relunctant to do so, i should be pressured/compelled by some authority. Even if that chance of only 3/1000 of a collision occurring is accurate, one cannot afford such repeated trials over and over again. I mean, i have no idea how frequent such close encounters are supposed to be, but if there's another one only a week after, you can't afford to gamble like that. It may even be an acceptable risk for the satellite's operator, but any such collision severely degrades the quality of orbital space. Oh, and by the way, asking how much fuel you'd be willing to spend to reduce the collision risk tenfold is misleading, since any actual manoeuver taken would reduce the risk to zero. It just has to be initiated soon enough. —Preceding unsigned comment added by 146.193.39.206 (talk) 17:47, 13 February 2009 (UTC)
 * Maneuver might reduce the risk to zero but depending on the fuel state of the satellite it might make the satellite's utility also zero, i.e. if it did not have enough fuel to maneuver back to a useful orbit. IN which case 99% chance of ahit is still better than 100% chance that your satellite will survive and be useless.
 * Yes, the satellite might be left stranded in a useless orbit. And restationing might therefore be a pointless action for the satellite operator. But everyone else (ie, the rest of world's population) also has a stake in it. No operator should be allowed to knowingly permit the generation of orbital garbage. That's why i argued for him to be forced to take action by some authority. It would be a net loss for the operator? So what? The situation is completely alike environmental regulations on the planet's surface: Many industries would like (at least at first glance) to be allowed to pollute no matter what, but still there are regulatory/enforcing procedures to make them behave. Being on an economically disadvantageous position never permitted such industries from walking out of their responsibilities.89.152.251.92 (talk) 01:06, 16 February 2009 (UTC)

And why should someone make the operator take avoidance action? It is the operators satellite - who does it hurt more than the operator if it goes down? And how do we know that the iridium operators didn't try and manourver and that teh Russian sat didn't also manoeuver and hit it on purpose? Or that the Russian's hadn't agreed to maneuver their sat but their maneuver failed. No enough info for real debate amongst s non rocket sceintists. —Preceding unsigned comment added by 219.90.144.59 (talk) 13:36, 14 February 2009 (UTC)

"absolutely no chance that they wouldn't know this was going to happen" Load of rubbish. Nasa frequently publishes "warnings" of "possible" collisions. Iridium satellites frequently appear in this list, but up till now, haven't actually suffered a collision DESPITE that they haven't manoeuvred their satellite. And the Russian satellite hasn't been operational since 1995. I think it is unlikely that the Russians would have been able to power it up 14 years later just to take out a communications satellite.


 * Oh, i see. So since it is possible to go from one place to another driving on the wrong side of the road without actually hitting anyone, is it ok to do it? And if you do it once, or twice, does it mean it is now safe to drive on the wrong side? The fact that Iridium satellites frequently appear on such collision warnings should tell you that they have been pushing their luck for quite some time (they and everyone who has been cramming up low earth orbit). Your argument is real cute: 'Well, they get warnings all the time. Since it never happened before, all those warnings were clearly bogus!' To use the very fact that you frequently receive warnings as an excuse to never do anything is really something else.89.152.251.92 (talk) 01:06, 16 February 2009 (UTC)

"since any actual manoeuvre taken would reduce the risk to zero." No it doesn't. If you make the wrong manoeuvre, you could actually increase the chance of a collision (of course, you might not realise at the time). That's why it's a Probability. And you don't want to be making lots of manoeuvres. It can slow your satellite down, and change it's orbit, increase atmospheric drag and that sort of thing. And what's to say that you don't then run the risk of hitting something else. And all the Iridium satellites are designed to work so that you can always see at least one at any given time. If you keep mucking around with the orbits, they won't be able to do so. —Preceding unsigned comment added by 86.174.122.122 (talk) 23:58, 14 February 2009 (UTC)


 * And why would you do the wrong manoeuver? Since when did orbital mechanics stop being deterministic? If it's a problem of you not trusting your navigators or equipment enough, then don't send junk up there. Any decently built and operated satellite would still have some risk associated with manoeuvering, sure, but that risk would be much, much lower than just doing nothing in a head-on encounter and crossing your fingers.89.152.251.92 (talk) 01:06, 16 February 2009 (UTC)

You miss my point. The data that Nasa provide on likely collisions isn't accurate. They don't predict definite "collisions". They predict "potential collisions". Manoeuvres may lower the probability of being hit, but unless you do something drastic (which is obviously a bad idea because you want to keep it in that orbit), it only lowers the probability, not takes it to zero.

I suppose you could class this as 'not trusting you navigators enough', but bearing in mind this is the first incident between a working satellite and another satellite, I'd say they're good enough to risk 'putting the junk up there'. Sure this is a "Since it never happened before, all those warnings were clearly bogus" argument, but ever heard of 'The Boy Who Cried Wolf'? —Preceding unsigned comment added by 86.174.122.122 (talk) 20:34, 17 February 2009 (UTC)


 * T S Kelso is about as close to "expert" on this topic as any civilian in the world. New Scientist quotes him as saying, ""There's no reason looking at the data that was available [to think the Russian satellite] was an immediate threat." (sdsds - talk) 05:21, 19 February 2009 (UTC)

Debris Velocity/Damage
I think it should be mentioned in this article that the debris will be travelling around 25000 kph relative to the ground, and so if any of it happens to cross paths with another satellite it will cause significant damage.  - ARC Gritt TALK  20:31, 12 February 2009 (UTC)

Perhaps, but the speed relative to the ground isn't a particularly great measure when you bear in mind that other satellites are travelling at the same speed. Although it appears that the debris is going to take an orbit that is neither polar nor geostationary/equatorial, which means it is more likely to cause damage to other satellites as it will be going in a different direction. —Preceding unsigned comment added by 86.131.102.102 (talk) 20:48, 12 February 2009 (UTC)


 * Added link to Kessler Syndrome in """See Also""" to give a little more info about the general issue of debris generated from impacts and their consequences. Sleet01 (talk) 21:01, 12 February 2009 (UTC)


 * Okay, to the extent that some portion of the orbital vectors of the two satellites were opposing--as is stated above--would it not be possible that some amount of satellite deceleration occurred in the brief time before the mechanical deformation split them into hundreds/thousands of pieces? If this occurred to any significant extent, might not the decelerated (slower) pieces of debris now decay their orbits more rapidly than they would have previously, as intact satellites?  Are there any spacecraft scientists or orbital physics folk who might offer an opinion?N2e (talk) 22:13, 12 February 2009 (UTC)

I would love to see some discussion of the collision mechanics. The Iridium is physically large, with large solar panels. The Kosmos had only 40 W of solar capacity, implying around 1/2 square meter of solar panel. It would be possible the Iridium could be largely in one piece, missing a panel, and spinning (no doubt radar would soon verify this). The near-right-angle hit would not retard its orbital velocity, and would arguably impart some velocity to the right of its original orbit, an impulse leading to an elliptical orbit. However, it would seem to me conservation of momentum must apply. Can the debris cloud overall gain velocity? In the head-on case, bus to bus, I would expect considerable vaporization, and much of the debris would be either robbed of orbital velocity, or directed so vertically as to be almost certain to intercept the atmosphere quickly. Tomligon (talk) 22:46, 12 February 2009 (UTC)

merge Kosmos-2251, Iridium 33

 * The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section. 

The result of the proposal was withdrawn, no consensus (non-admin) -- G W … 00:49, 14 February 2009 (UTC)

There is nothing to say in the satellite articles except that they belonged to their respective classes and collided. Are there any objections to redirecting them here? Potatoswatter (talk) 21:24, 12 February 2009 (UTC)

Hmm, just to justify this a bit.
 * 1) The articles have various statistics and numbers which are more difficult to verify in multiple individual articles than this one. So information will be more timely and reliable with just this one article to build & verify.
 * 2) Neither sat article existed before.
 * 3) Commsats of a network are inherently indistinguishable aside from the launch date and longitude. Potatoswatter (talk) 21:39, 12 February 2009 (UTC)


 * Oppose. Satellites are notable as individual entities. They are fairly new articles, and have not yet been given time to develop and gain more content. -- G W … 21:30, 12 February 2009 (UTC)
 * Communication satellites are notable individually? What is a commsat even capable of doing individually? Potatoswatter (talk) 21:35, 12 February 2009 (UTC)
 * In the absence of any guidelines, the de facto standard is that all satellites are, by definition, notable. -- G W … 21:38, 12 February 2009 (UTC)
 * I'm not rummaging through the guidelines now, but WP:ONEVENT covers the issue pretty well for people. Are indistinguishable satellites somehow more interesting than people? Potatoswatter (talk) 21:44, 12 February 2009 (UTC)
 * Yes. But that is not the issue here. Under the de facto interpretation of notability guidelines, the satellite is notable because it is a satellite. -- G W … 21:49, 12 February 2009 (UTC)


 * Potatoswatter, yes, indistinguishable satellites are notable by default - considering their relative rareness compared to your indistinguishable human. Kingturtle (talk) 21:53, 12 February 2009 (UTC)
 * In response to the three points you have added, I can see no evidence to support #1, #2 is irrelevant, and #3 is incorrect. -- G  W … 21:43, 12 February 2009 (UTC)
 * Oppose. This article is about one specific event. The other articles are about specific things, which had relevant information before this event took place. Grundle2600 (talk) 21:36, 12 February 2009 (UTC)
 * The other articles did not have relevant information before this event took place. They were created in response to this event.  See their initial versions from yesterday,  and . TJRC (talk) 00:40, 13 February 2009 (UTC)
 * Oh wow! You're right - I was wrong. Grundle2600 (talk) 01:09, 13 February 2009 (UTC)
 * Oppose As above, the satelite was notable (ish!) on it's own, even if it took this event to get the article going. Extreme example, based on WP:ONEEVENT but I don't think we are going to merge Lee Harvey Oswald into JFK. (sorry, I know it's a bit of a strawman and it's a lazy example but it does get my point) M&spades;ssing   Ace  23:10, 12 February 2009 (UTC)
 * Oppose As Ace . I agree with your example and am pretty certain this first of its kind event is notable enough for its own article. Deethen (talk) 23:37, 12 February 2009 (UTC)
 * Oppose What Ace said. Articles in question have distinctly different purposes. One documents a satellite, another documents an event. Also, there will almost certainly information relevant to a general knowledge about the satellite that, although notable, will in no way be relevant to this event. Spacmanspif300 (talk) 23:51, 12 February 2009 (UTC)
 * In reality, the two that purport to document the satellites only document this event; and the satellite articles clearly do not have a different purpose than this article.TJRC (talk) 00:38, 13 February 2009 (UTC)


 * Merge I don't understand this opposition to merge. Both articles were created yesterday, solely to hold information about the collision.  It's got WP:COATRACK and WP:ONEEVENT all over it.  Every satellite is inherently individually notable?  I find that hard to swallow.  I find it particularly hard to swallow that, in the absence of a specific guideline, a thing is deemed notable.  There's a big " &#91;citation needed&#93;  " all over that one.  What does anyone seriously think either of those articles are going to become?  They're never going to have anything beyond a discussion of the collision that is the subject of this article.  TJRC (talk) 00:35, 13 February 2009 (UTC)
 * To elaborate (but hopefully not belabor) that last point, and at the risk of stating the obvious, nothing more is going to ver happen with either satellite, now that they're destroyed.  Not much chance of either article growing beyond a stub.  The only stuff worth putting in there is already there, and duplicative of what's here.  TJRC (talk) 01:27, 13 February 2009 (UTC)


 * Oppose The pattern seems to be that many individual stars, galaxies, and even asteroids each are getting their own article despite the fact that many of these are not particularly notable in themselves. Separate articles will also allow for the gathering of information specific to that satellite or the collision event as RS are found. With Iridium, a single article about all the satellites with a table would suffice except that Iridium 33 itself is now notable. --Marc Kupper|talk 00:39, 13 February 2009 (UTC)
 * Natural astronomical objects are each subjects of research. Each is unique, even if many have not "made the news." Commsats are mass produced. There should be articles for the types of satellites that these were (there unfortunately aren't), but the satellites themselves were not unique aside from their orbits (ie locations). This is like having an article on a plane which crashed, in addition to the article on the crash itself (ie both TWA Flight 800 plus Tail number N93119). Potatoswatter (talk) 06:03, 13 February 2009 (UTC)
 * MergeTrilobitealive (talk) 01:51, 13 February 2009 (UTC)
 * Oppose The satellites were notable before the incident, even if the articles were not created until after. I have no opposition to revisiting this issue if the articles have not expanded in 6 months. -MBK004 01:56, 13 February 2009 (UTC)


 * Merge or redirect:
 * 1) Iridium 33 was one of a constellation of 66 identical satellites (plus spares?). The constellation, the technology, the history, the project, etc.—that is, all encyclopedic content—is in a comprehensive article: Iridium (satellite). So far as I am aware, none of the other 65 Iridium satellites is the subject of its own Wikipedia article.


 * 1) Kosmos-2251 was a retired Russian Strela military communications satellite. The Strela satellites are the subject of a stub created 7 June 2008 with no edits until the crash: Strela (satellite). So far as I am aware, none of the other Strela satellites is the subject of its own Wikipedia article.


 * These facts show that (1) prior to the the collision, there was nothing that warranted a Wikipedia article on either satellite; and (2) they are notable now only because of the 2009 satellite collision, which is, beyond doubt, an historic event. It is in that (i.e., this) article that the stories of these two particular satellites belong. Indeed, from what I see, all the information in the Iridium 33 and Kosmos-2251 articles is a repeat of the information and source citations that is already in 2009 satellite collision, which is where the information about the collision participants belongs. There is no justification for repeating this information in other articles, and such repetition is contrary to Wikipedia's design: that's what wikilinks are for. If there is some content in Iridium 33 and Kosmos-2251 that is not in 2009 satellite collision—and if there is any, there isn't much—then that information can be merged into 2009 satellite collision. If there is none, then the two articles become redirects to 2009 satellite collision. While I agree with the remarks above that normally one would give a just-created article time to develop before proposing to merge it, in this particular case, it is clear that there is nothing more to develop about the two individual satellites other than as more information develops about the 2009 satellite collision. Finell (Talk) 02:39, 13 February 2009 (UTC)


 * Not that this we'll win this debate (for now) anyway, but I'm gonna preempt the other guys to point out that the 66+ satellites aren't necessarily all identical. However many of them are, and the best way to describe them would be in Iridium (satellite), after splitting off a new article Iridium Satellite LLC. Potatoswatter (talk) 06:12, 13 February 2009 (UTC)


 * Oppose, as they achieve individual notability. Tavix (talk) 04:03, 13 February 2009 (UTC)


 * Oppose Iridium 33 should merge to the model of Iridium satellite that this one is (or build an article on that model of satellite). And so should the Kosmos (to the Strela 2M article) 76.66.196.229 (talk) 06:02, 13 February 2009 (UTC)
 * Oppose per Tavix Kuralyov (talk) 06:07, 13 February 2009 (UTC)


 * Oppose Why would you want to merge it? A satellite of any kind is a technological piece worth of its own article..who came up with this guys?.--Camilo Sanchez (talk) 13:21, 13 February 2009 (UTC)


 * Question: Do those of you who argue that every individual satellite is unique and warrants its own article intend to:
 * Write an article on each of the other 65 Iridium satellites?
 * Write an article on each of the other (I don't know how many) Strela satellites?
 * Then, write an article on each individual satellite ever launched?


 * If not, then you aren't being consistent. Finell (Talk) 16:34, 13 February 2009 (UTC)


 * Another question: Please identify the specific content in the Iridium 33 and Kosmos-2251 articles that is not a repeat of content in 2009 satellite collision? Finell (Talk) 16:34, 13 February 2009 (UTC)
 * 1)Yes, 2)Yes, 3)Yes, 4)Descriptions of launch, orbit, operations, etc are more detailed, and there is room to expand when research is conducted into this satellite's operational history. -- G W … 18:03, 13 February 2009 (UTC)


 * Merge This is a short stub. Kilmer-san (talk) 17:20, 13 February 2009 (UTC)


 * Merge - No content in each individual article that isn't already here.  Grsz 11  17:35, 13 February 2009 (UTC)


 * Merge - Both articles duplicate all contents found here. More over, in the case of Irridium 33, if the accident hadn't of occured there would be nothing noteworthy whatever about that one; an article about the Irridium satlelight model in general would adequately describe all of them. (The Kosmos ones may have sub classes worthy of their own articles, but we don't certaintely don't need 2251+ of them either.) Jon (talk) 22:57, 13 February 2009 (UTC)


 * Potatoswatter seems to have withdrawn the merger request for now, so I have closed the poll. -- G W … 00:49, 14 February 2009 (UTC)
 * The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

smaller collision vs. major
What makes this major and the others smaller? Kingturtle (talk) 21:45, 12 February 2009 (UTC)
 * The fact that both satellites were completely destroyed, and the amount of debris produced. -- G W … 21:52, 12 February 2009 (UTC)
 * Can you make that answer more explicit in the article? Kingturtle (talk) 21:54, 12 February 2009 (UTC)

Proposed move
I am not a huge fan of the current name, 2009 satellite collision. First of all, we are assuming this is going to be the only satellite collision in this year, while although these events are rare, we can't be for sure this will be the case. Second, the name really isn't a good descriptor. Remember that "satellite" doesn't just mean man made satellites, they can also refer to as moons as well. So for example, someone could read the title and think two of Jupiter's moons collided or something of that nature. Because of this, I would like to suggest a new name for the article: something along the lines of Collision of Iridium 33 and Kosmos-2251. Thoughts? Tavix (talk) 04:10, 13 February 2009 (UTC)


 * I would tend to agree. We're only six weeks into the year, with another 46 to go. Unless the various satellite owners figure out a way to avoid each others paths, this could very well happen again. Perhaps sooner than later. Glenn L (talk) 05:05, 13 February 2009 (UTC)


 * I vote to move (over redirect) to Satellite collision. There isn't ambiguity as natural satellites are called moons. The unfortunate thing, which makes this historic, is that one such collision raises the probability of others. But for now, the specific information is what we have on the general topic. An encyclopedia covers general topics before adding an article for every specific event and item. Potatoswatter (talk) 06:21, 13 February 2009 (UTC)
 * I would oppose a move over satellite collision, and instead suggest that be made into a real article, on actual, predicted and theoretical satellite collisions and their effects. 76.66.196.229 (talk) 06:39, 13 February 2009 (UTC)
 * Theoretical, predicted are Ablation cascade, Kessler Syndrome respectively. Potatoswatter (talk) 06:43, 13 February 2009 (UTC)
 * IOW, a dab page should be built now, awaiting someone writing summary sections and using main 76.66.196.229 (talk) 07:25, 13 February 2009 (UTC)


 * I prefer Iridium 33–Kosmos-2251 satellite collision myself. Sceptre (talk) 13:02, 13 February 2009 (UTC)


 * When I created this article, I didn't know what to call it, so I called it what I did - I thought someone might later propose a different name. A move is fine with me, as long as the article is still exclusively about this one particular event. I'd like to suggest February 10, 2009 satellite collision as one possibility - the reason the link is already blue is because I had already created it as a redirect.Grundle2600 (talk) 15:14, 13 February 2009 (UTC)


 * Has anyone looked at WP:NAME for guidance? Satellite collision is definitely too broad; it does not indicate that the article is about one specific collision. Consider Satellite collision of February 10, 2009 or Iridium–Kosmos satellite collision. But above all, look at WP:NAME. Finell (Talk) 16:43, 13 February 2009 (UTC)


 * How about First major satellite collision? (sdsds - talk) 17:18, 13 February 2009 (UTC)


 * I would prefer leaving the exact date out of the title. I can't really see a problem with the current title at the moment - it fits with titles of similar titles such as 2009 Malagasy protests. If there is another collision, we can move it then. If we have to move it, would suggest either February 2009 satellite collision or Collision of Iridium 33 and Kosmos-2251. -- G W … 18:08, 13 February 2009 (UTC)


 * User:GW Simulations echoes my thoughts exactly. YAGNI.  We're worrying that, if there's a second collision in 2009, then this article title will be ambiguous.  In the first place, that's pretty unlikely, but if it happens, we can retitle it then.  If there's no second collision, then the current title remains perfect.  TJRC (talk) 19:24, 13 February 2009 (UTC)

Survey

 * The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section. 

The result of the proposal was no consensus to support move. JPG-GR (talk) 05:33, 20 February 2009 (UTC)


 * 2009 satellite collision →  — This was proposed at the talk page of the article and the general consensus is that "Collision of Iridium 33 and Kosmos-2251 is the best choice. —
 * I don't see a consensus on the talk page to move to that name. – ukexpat (talk) 22:10, 13 February 2009 (UTC)


 * Oppose per my post above, although the proposed title is better than the alternatives, I still prefer the current one. -- G W … 13:30, 14 February 2009 (UTC)
 * Oppose in preference of "Iridium( 33)—Kosmos( 2251) satellite collision". Sceptre (talk) 21:34, 14 February 2009 (UTC)


 * Oppose Sceptre-"Iridium 33–Kosmos-2251 satellite collision " Seconded. 86.174.122.122 (talk) 00:00, 15 February 2009 (UTC)
 * Oppose per my comment above. Name is correct as is.  This should be revisited if there's a second collision this year. TJRC (talk) 02:37, 15 February 2009 (UTC)
 * Comment - furthermore, I dispute the characterization that there is any consensus to move to "Collision of Iridium 33 and Kosmos-2251". TJRC (talk) 02:37, 15 February 2009 (UTC)


 * Oppose. Current name is more recognizable than proposed one. Dekimasu よ! 02:56, 16 February 2009 (UTC)
 * I'll point out that the current name is totally ambiguous. Besides assuming only one significant one of these impacts occurs this this year, collision is also a problem.  Collisions occur all of the time.  This article is specifically about the impact of two satellites that were earth launched with each other.  The title does not convey that point.  Satellites that experience impact from any object represent a satellite collision. Vegaswikian (talk) 18:10, 18 February 2009 (UTC)
 * That would be preemptive disambiguation. If there is any other article this title could be confused with right now (any notable collision an article could be written about?), let me know. Dekimasu よ! 03:41, 19 February 2009 (UTC)
 * Support move to Iridium–Kosmos satellite collision Iridium–Kosmos collision. I'm far from convinced that the current name is better known. Vegaswikian (talk) 07:19, 17 February 2009 (UTC)
 * Oppose. Once there is a second collision this year, we can discuss what to do. Deethen (talk) 23:10, 18 February 2009 (UTC)
 * Support a move, but oppose to the proposed title. The term "satellite collision" should definitely part of the page name, since that is what people will search for. The term "collision" by itself is by far too broad if you don't know what Iridium and Kosmos are. Something in the line of "Satellite collision Iridium–Kosmos", or "Satellite collision of Iridium 33 and Kosmos-2251", or "Satellite collision of February 10, 2009'", as already suggested above, sounds more reasonable. --Cruncher (talk) 05:23, 19 February 2009 (UTC)
 * Comment - Amazingly we now have HMS Vanguard and Triomphant submarine collision. Would there be benefit to consistency in naming between these two events? (sdsds - talk) 05:32, 20 February 2009 (UTC)
 * The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Strela 2M
A photo of the Kosmos model should be added. 76.66.196.229 (talk) 06:28, 13 February 2009 (UTC)
 * I've added the "in" feature to this template to make a point in somewhat of a jocular manner: where would we get a photo of the satellite? Nyttend (talk) 07:21, 13 February 2009 (UTC)
 * Astronautix.de as referenced here has some kind of pic. Potatoswatter (talk) 07:26, 13 February 2009 (UTC)
 * A press picture from . Whether that's accurate is the next question - this image looks different... --Cruncher (talk) 05:05, 19 February 2009 (UTC)

Computing Collision Speed
Computing estimated Collision Speed is not a research per se. It is basically using known mathematical formulas and constants (like Mass of the Earth and Gravitational constant) also collision angle is based computing orbits from NORAD TLEs. So I think this section should not be noted as Original Research. —Preceding unsigned comment added by Amoeba000 (talk • contribs) 22:25, 14 February 2009 (UTC)
 * Agreed. Some editors take select Wikipedia rules to an extreme, and ignore other conflicting guidelines that common sense says should have priority. The section on estimated collision speed is helpful for a wide variety of readers. DBrnstn (talk) 03:46, 16 February 2009 (UTC)

Would it be okay to present the English equivalents of the metric measures on this section of the article? --68.60.67.149 (talk) 23:08, 14 February 2009 (UTC)

That would be OK. —Preceding unsigned comment added by 92.55.98.115 (talk) 10:27, 15 February 2009 (UTC)

Thank you. --68.60.67.149 (talk) 16:39, 15 February 2009 (UTC)

Original Research
The article now shows Hugh Lewis's calculated collision speed of 42120 km/h which is exactly 11.7 metres per second and probably rounded. However, it is a big improvement on CNN's figure, and I am happy with the current approximation.

Meanwhile, for curiosity's sake, here is the Collision speed computation (removed from the article as Original Research). I have tweaked the numbers and added a few cites.

It assumes both satellite orbits are perfectly circular when they are in fact ellipses. It also assumes the Earth is spherical and homogenous (it's not). The first assumption will under-calculate collision velocities close to perigee. Using a 789 km collision altitude and 102.2 collision angle yields 11.62 km/s. But using 776 km collision altitude (from JSR) and 102.46 collision angle (from a physics forum) I get 11.65 km/s (which verifies BobG's calculation).



The approximate collision speed is based on the velocities of the satellites and the angle at which they collided. Estimated speed of each satellite at an altitude of approximately 789 kilometers above earth was v=7.467 m/s. This is computed by the formula for speed of a satellite in circular orbit which is $$v=\sqrt{\frac{G{\times}M}{r}}$$, where G is the gravitational constant (6.6726 E-11 (N-m2)/kg2), M is the mass of the combined planet/satellite system (Earth's mass is 5.9736 E24 kg), and r is the radius of the orbit measured from the planet's center in our case r=7,149 Km.

The angle at which the satellites collided was measured using Satellite tracking software (Simulation des GPS v2.41), and was approximately 102.2 degrees. Other sources have 102.46 degrees. The input data for the tracking software were from updated NORAD TLE.

The combined collision speed is as follows: $$V=2v{\times}{\sin{({\frac{angle}{2}})}}$$, which gives 41840 km/h (or 11.622 kilometres per second).

The Orlando Sentinel reports the event to have been, "what amounted to a 26,000 mph collision."

84user (talk) 03:21, 17 February 2009 (UTC)

Out of control
'Russia has not commented on claims the satellite was out of control.' The term 'out of control' suggests the russian satellite did something unexpected thereby being at fault, causing the accident. If there is no evidence for that unexpected move (reference) this statement should be removed since article&ref contain an unverifiable claim harming NPOV. 82.95.200.104 (talk) 23:34, 14 February 2009 (UTC)

Perhaps "There is no reason to suspect that any malicous action was involved, since the Russian satellite had been defunct since 1995 (I'll get the reference later). Russia has not commented on whether the satellite was out of control"

Although it's not really neutral, but it is a balance POV.86.174.122.122 (talk) 00:04, 15 February 2009 (UTC)


 * Out of control implies that the satellite was making random orbital changes. If it was a dead piece of space junk it should have a completely predictable orbit. Even if it wasn't "controlled"... 76.66.196.229 (talk) 05:50, 15 February 2009 (UTC)

The whole sentence should be removed because it is false. The head of the Russian Space Forces was quoted in the Moscow Times as saying they haven't used it since at least 1995. (An astronautix.com article actually says the Strela-2M's were superceded by a constellation of Strela 3-M's in 1994.) And BTW, orbits are not "completely predictable". There are lots of chaotic forces, gravitational moments, drag, the Moon, magnetic fields, etc. It fact, the Cosmos 2251 was actually INCREASING in altitude at the time of the collision. Rather strange for an unpowered craft, wouldn't you say? --Warren Platts 75.68.200.190 (talk) 18:31, 19 February 2009 (UTC)


 * The spacecraft was designed to maintain its orientation passively, i.e. with a gravity boom. Thus an ongoing process on the "inactive" satellite, such as a slow leak of residual pressurized gas, could have been causing a slight propulsive effect. This could explain a net increase in altitude. It also seems plausible that an orbit change could occur even without coherent spacecraft orientation if, say, a gasket failed thereby releasing a large amount of residual gas with an impulsive result. And too, the orbit of the spacecraft might have changed if, prior to colliding with the Iridium satellite, it had been hit by some other, smaller piece of space debris. All of this is speculation of course, but is the phrase, "no longer under active control" (as currently used in the article) consistent with all these possibilities? (sdsds - talk) 19:47, 19 February 2009 (UTC)

Has it not occured to anyone that the orbit is slightly elliptical, so when it is moving perigee to apogee, it's altitude will increase?86.150.129.117 (talk) 22:57, 23 February 2009 (UTC)


 * Yes, you are correct, and that explains an altitude that changes during the course of an orbit. It doesn't, however, explain a change in the orbit itself. A change in orbit would need to be caused by some other effect. Either something large, like the hypothesis listed above, or perhaps simply an unfortunate coincidence of small factors like uneven gravitation from Earth, or gravitational influences of the Moon, the Sun etc. (sdsds - talk) 01:44, 24 February 2009 (UTC)


 * The Moon itself is "gaining altitude"; if such a big rock can "fly" i wouldn't be surprised a relatively tiny man made object can as well. --TiagoTiago (talk) 15:02, 7 November 2011 (UTC)

Consistency
It appears that there are a number of inconsistencies in the exact data about the collision at the moment. (My) previous comment about the mass of the Russian satellite is a case and point. The (nice) picture depicting the point of collision claims that the collision was at a different altitude to that in the main article. I suggest that we should decide on a value for it and stick with that. I know this might seem to be nit-picking, but even if we are unsure of the correct value, I think we should at least be consistent. 86.174.122.122 (talk) 21:23, 15 February 2009 (UTC)

I have since found two sites that agree on a value of 789/790km: http://www.n2yo.com/collision-between-two-satellites.php http://www.space.com/news/090211-satellite-collision.html

I suggest we use this value. —Preceding unsigned comment added by 86.174.122.122 (talk) 23:16, 15 February 2009 (UTC)

In the interest of consistency, I have to support a title that refers to the actual satellites. If you go to the disambiguation page for satellite collisions: http://en.wikipedia.org/wiki/Satellite_collision. then you'll see the other 'collisions' are labelled by the satellites that collided.86.150.129.117 (talk) 21:15, 7 March 2009 (UTC)

impact
There should be something about the impact to the Iridium network, communications, risks, etc 76.66.196.229 (talk) 07:43, 17 February 2009 (UTC)

*Why* did they collide?
This entry doesn't explain *why* they collided. Was there some mistake in calculating the orbits? Did some equipment malfunction? --209.203.125.162 (talk) 19:04, 16 December 2013 (UTC)
 * There was no real "reason" that it happened. A lot of low-orbit communications satellites use ~800 km orbits with varying inclinations; if you stick enough of them up there eventually two are going to end up trying to occupy the same space at the same time. -- W.  D.   Graham  19:12, 16 December 2013 (UTC)

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Clarification Needed (perhaps)
"Space News listed the collision as the fourth biggest fragmentation event in history," - is that the biggest space fragmentation? what is a "fragmentation event"? I can believe this is the fourth biggest space fragmentation event, but surely at least four things in history have fragmented into more pieces...? — Preceding unsigned comment added by 165.225.50.89 (talk) 23:30, 22 February 2019 (UTC)