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Larry Jacks
2009-Feb-11, 09:32 PM
So much for the "big sky" theory of collision avoidance.

US And Russian Satellites Collide (http://www.cbsnews.com/stories/2009/02/11/tech/main4792976.shtml)

A commercial Iridium communications satellite collided with a Russian satellite or satellite fragment, Tuesday, creating a cloud of wreckage in low-Earth orbit, officials said Wednesday. The international space station is not threatened by the debris, they said, but it's not yet clear whether it poses a risk to any other satellites in similar orbits.

"Everybody is saying the risk is minimal to NASA assets," said an agency manager who asked not to be identified.

Once source said U.S. Space Command was tracking about 280 pieces of debris, most of it from the defunct Russian satellite. A spokesman for U.S. Space Command was not aware of the incident but he said he would try to track down additional details. Calls to Iridium Satellite LLC were not immediately returned.

Other than the part about US Space Command (which has not existed for years), the article is correct.

ToSeek
2009-Feb-11, 09:35 PM
Two satellites collide in orbit (http://spaceflightnow.com/news/n0902/11iridium/)


Asked which satellite was at fault, Johnson said "they ran into each other. Nothing has the right of way up there. We don't have an air traffic controller in space. There is no universal way of knowing what's coming in your direction."

NEOWatcher
2009-Feb-11, 09:35 PM
So much for the "big sky" theory of collision avoidance.
Ouch;
It's going to be interesting to see some of the details, like expected orbit decays and satellite details.
(which entry in Heavens-Above do I ignore now?)

jfribrg
2009-Feb-11, 10:45 PM
Here (http://news.yahoo.com/s/ap/20090211/ap_on_sc/satellite_collision) is another article about the same event. They give more info about the Russian sattelite:

The collision involved ...a Russian satellite launched in 1933 and believed to be non-functionningThose Russians really were way ahead of us in the space race.

No doubt the typo will be corrected within a few minutes of me posting this.

Larry Jacks
2009-Feb-11, 10:53 PM
It's going to be interesting to see some of the details, like expected orbit decays and satellite details.

Due to my job, I know more about this event than I can say. The satellites were high enough that many pieces will be up there for decades, perhaps as long as a century. The Iridium is in a near polar orbit. That means the pieces will sweep across many other orbits, increasing the chances of further collisions. This most definitely is not good.

AGN Fuel
2009-Feb-12, 02:15 AM
Asked which satellite was at fault, Johnson said "they ran into each other. Nothing has the right of way up there. We don't have an air traffic controller in space. There is no universal way of knowing what's coming in your direction."

They needed to find out though to sort out who was going to lose their No-Claim Bonus.

Josh
2009-Feb-12, 02:37 AM
Isn't this the first collision of two satellites in space? Not bad considering the number of satellites that are wherring around up there (I read it's about 8000 in orbit ... not including those in decay - can anyone clarify?).

schlaugh
2009-Feb-12, 02:52 AM
Apparently satellites have collided before, but none this large. From the NY Times:


“This is a first, unfortunately,” Nicholas L. Johnson, chief scientist for orbital debris at the National Aeronautics and Space Administration (http://topics.nytimes.com/top/reference/timestopics/organizations/n/national_aeronautics_and_space_administration/index.html?inline=nyt-org), said of the collision.It happened some 490 miles above northern Siberia, at around noon Eastern time. Two communications satellites — one Russian, one American — cracked up in silent destruction. In the aftermath, military radars on the ground tracked large amounts of debris going into higher and lower orbits.
“Nothing to this extent” has ever happened before, Mr. Johnson said. “We’ve had three other accidental collisions between what we call catalog objects, but they were all much smaller than this,” the objects always very small and moderate in size.

Full story (http://www.nytimes.com/2009/02/12/science/space/12satellite.html?hp)

Solfe
2009-Feb-12, 04:10 AM
Clicking the first link, does anyone else see the irony in the headline "U.S. And Russian Satellites Collide"? There is a picture of the ISS at the just below that. :)

Solfe

eburacum45
2009-Feb-12, 07:18 AM
The Kessler Syndrome springs to mind;
http://en.wikipedia.org/wiki/Kessler_Syndrome

NEOWatcher
2009-Feb-12, 01:24 PM
It's going to be interesting to see some of the details, like expected orbit decays and satellite details.

Due to my job, I know more about this event than I can say. The satellites were high enough that many pieces will be up there for decades, perhaps as long as a century. The Iridium is in a near polar orbit. That means the pieces will sweep across many other orbits, increasing the chances of further collisions. This most definitely is not good.
Yes; I remember a chart of altitude vs decay.
I was thinking more about how the angles of impact could affect the trajectories and elongations of the orbits of some of the pieces possibly bringing perigee to or near the atmosphere.

Buttercup
2009-Feb-12, 01:30 PM
This article puts the blame on the Russians:

http://news.yahoo.com/s/ap/satellite_collision


NASA said it will take weeks to determine the full magnitude of the unprecedented crash and whether any other satellites or even the Hubble Space Telescope are threatened.

The collision, which occurred nearly 500 miles over Siberia on Tuesday, was the first high-speed impact between two intact spacecraft, NASA officials said.

"We knew this was going to happen eventually..."

NASA believes any risk to the ISS and its three astronauts is low. It orbits about 270 miles below the collision course.

And look at that artist's impression of all the space junk around Earth. :( They estimate this collision has created perhaps HUNDREDS of bits of debris. :(

NEOWatcher
2009-Feb-12, 01:45 PM
This article puts the blame on the Russians:
They went as far as excusing Iridium, but didn't go as far as putting blame on the Russians either. It still infers no-fault.
But; the natural tendency of a conclusion will be to blame the derelict. In reality, the only way to blame someone is if the non-derelict could have maneuvered to avoid it. I doubt that would be a common case, but it would be the tracking authority itself that is to blame.


And look at that artist's impression of all the space junk around Earth. :(
That doesn't even show the higher orbits. Look at the one on the wiki page for space debris (http://en.wikipedia.org/wiki/File:Debris-GEO1280.jpg). Not as good resolution though.

Buttercup
2009-Feb-12, 02:15 PM
Thanks NEOWatcher.

I'm wondering at what point/how swiftly the atmosphere will become so junked up it'll begin seriously interfering with manned spaceflight [and especially beyond LEO].

We should have maintained the Apollo momentum, but thanks to Pres. Nixon...[will defer mini-tangent].

NEOWatcher
2009-Feb-12, 02:20 PM
We should have maintained the Apollo momentum, but thanks to Pres. Nixon...[will defer mini-tangent].
I absolutely agree with you, but how does that relate to the space debris problem?
It's the un-manned and commercial applications that are mostly causing the problem.

Buttercup
2009-Feb-12, 03:17 PM
I was just blowing off a bit of steam, NEO. :)

Here's more from www.spaceweather.com [today's date/site archives daily]:


The expanding cloud of debris contains more than 300 fragments...

The US Air Force Space Surveillance Radar in Texas reportedly detected echoes from the debris cloud when it passed over the facility on Feb. 11th. Spaceweather.com is streaming live audio from the radar, and it might be possible to hear echoes the next time the cloud passes overhead.

Try listening on Thursday, Feb. 12th, between 4:14 pm and 4:24 pm CST (2214 - 2224 UT). That's when Kosmos 2251 would have passed over the radar intact had the satellite not been shattered. More listening opportunities will be posted when the location of the debris is better known.

Live audio link: http://wowzaweb.streamguys.com/%7Espaceweather/

A map of the collision [also courtesy spaceweather.com]:

http://tinyurl.com/czhtjl

If it weren't for the space debris issue, it'd be like "Oh cool!" :D But it's not cool. :(

NEOWatcher
2009-Feb-12, 03:30 PM
I was just blowing off a bit of steam, NEO. :)
Sometimes it's good to let it out. Sometimes not. This time just confused me.


Here's more from www.spaceweather.com (http://www.spaceweather.com) [today's date/site archives daily]:
I know it's correct, but there's something about "listening" to radar that just sounds funny to me.

Buttercup
2009-Feb-12, 03:37 PM
I know it's correct, but there's something about "listening" to radar that just sounds funny to me.

Yeah. :) I might try it [if this computer will allow].

Same goes for meteor showers; never "listened" to one of those either [the site posts live audio of them as well]. Would rather watch. Back on topic...

Gigabyte
2009-Feb-12, 04:20 PM
February 6, 2007

For decades, space experts have worried that a speeding bit of orbital debris might one day smash a large spacecraft into hundreds of pieces and start a chain reaction, a slow cascade of collisions that would expand for centuries, spreading chaos through the heavens.

In the last decade or so, as scientists came to agree that the number of objects in orbit had surpassed a critical mass — or, in their terms, the critical spatial density, the point at which a chain reaction becomes inevitable — they grew more anxious.
http://www.nytimes.com/2007/02/06/science/space/06orbi.html?_r=1

Why do I have a bad feeling about this?

Chuck
2009-Feb-12, 04:45 PM
Yet another explanation for the apparent absence of alien civilizations. Their planets are encased in spheres of satellite debris.

Argos
2009-Feb-12, 04:47 PM
It is obvious that something has to be done about it. And the obvious thing that comes to mind is

a) establishing international agreements demanding that satellites be equipped with some kind deorbiting capability and/or

b) establishing expiration dates for all kinds of satellites, with compulsory deorbiting.

geonuc
2009-Feb-12, 05:08 PM
Help me understand some things about satellites.

The altitude a satellite orbits the earth is determined by it's velocity, right? Low altitude stuff like the ISS are really zipping along, and geo-stationary (geo-synchronous?) satellites, are, well, stationary.

So, for a collision to occur, it must be between two non-geo-stationary satellites, and further, travelling at the same speed.

I would think the Iridium satellites would be stationary. If so, how did it collide with anything?

Argos
2009-Feb-12, 05:25 PM
Help me understand some things about satellites.

The altitude a satellite orbits the earth is determined by it's velocity, right? Low altitude stuff like the ISS are really zipping along, and geo-stationary (geo-synchronous?) satellites, are, well, stationary.

AFAIK, Iridium satellites are not geosynchronous. They orbit at about the same altitude the collision occurred. Two satellites at the same speed and altitude can collide if their orbital inclinations are different.

Geo-stationary satellites are only stationary relative to the surface. They have orbital velocity as any other satellite.

Gandalf223
2009-Feb-12, 05:44 PM
This article puts the blame on the Russians:

http://news.yahoo.com/s/ap/satellite_collision

There's no blame-placing that I can see, nor can there be. Blame must be shared equally among all parties who put stuff up into orbit without a driver...

NEOWatcher
2009-Feb-12, 05:45 PM
Help me understand some things about satellites.
...and geo-stationary (geo-synchronous?) satellites, are, well, stationary.
To expand on Argos' comment.
the "geo-" means relative to the earth. The earth spins, so naturally the satellites move to compensate.
Geo-stationary means stationary to one point on the earth.
Geo-synchronous means in synchronization to the earth. This one only means that the satellite will be above the same place once a day.

Geo-stationary is about 22000 miles up, or travel a circumference of (4000+22000)*2*pi = ~165000 or around 6800mph.


I would think the Iridium satellites would be stationary. If so, how did it collide with anything?
That might come to mind when you're thinking communication satellites, but these are not directional in the same manner as having to direct the signal toward them. You lock on to whatever satellite is passing, and the signal will be passed from sat to sat as they pass (like travelling past cell towers)
GPS is kind of the same thing.

geonuc
2009-Feb-12, 05:45 PM
AFAIK, Iridium satellites are not geosynchronous. They orbit at about the same altittude the collision occurred. Two satellites at the same speed and altittude can collide if their orbital inclinations are different.

Geo-stationary satellites are only stationary relative to the surface. They have orbital velocity as any other satellite.
Yeah, that's what I meant - stationary relative to the earth's surface.

So, these two satellites must have been on different trajectories.

Do any satellites orbit in the opposite direction? Are head-on collisions a risk?

NEOWatcher
2009-Feb-12, 05:52 PM
Do any satellites orbit in the opposite direction? Are head-on collisions a risk?
When you are talking about a circular orbit, the concept of opposite direction can get a little tricky.
You would need at least one in a retrograde orbit for it to be truly opposite. Polar orbits might be a possibility, they do cross, but actual proximity might be rare.

Pretty much any angle is going to be a disaster.

Head on, might actually be preferable. You have a much better chance of some of the debris' velocity to be cancelled out.

NEOWatcher
2009-Feb-12, 05:57 PM
By the way. A visualization might help.

I've always found J-track 3d (http://science.nasa.gov/Realtime/jtrack/3d/JTrack3d.html) at nasa to be pretty cool and helpful for visualiztions.
You can speed up the refresh and timing to get a feel for what thier orbit looks like, and you can select the sats, and see how they track projected onto the earth's surface.

Gandalf223
2009-Feb-12, 06:01 PM
The altitude a satellite orbits the earth is determined by it's velocity, right? Low altitude stuff like the ISS are really zipping along, and geo-stationary (geo-synchronous?) satellites, are, well, stationary.

Geostationary satellites only appear to be stationary; in fact they are zipping along at exactly the right speed to remain above the same point on earth's equator.

Geostationary satellites are moving about 6,800 MPH or so, compared to around 18,000 MPH for low earth orbits.

NEOWatcher
2009-Feb-12, 06:04 PM
Geostationary...
Ok; that's twice you repeated me in this thread. :think:

Argos
2009-Feb-12, 06:07 PM
Do any satellites orbit in the opposite direction? Are head-on collisions a risk?

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.

mahesh
2009-Feb-12, 06:25 PM
Isn't this the first collision of two satellites in space? Not bad considering the number of satellites that are wherring around up there (I read it's about 8000 in orbit ... not including those in decay - can anyone clarify?).

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



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

geonuc
2009-Feb-12, 06:26 PM
To expand on Argos' comment.
the "geo-" means relative to the earth. The earth spins, so naturally the satellites move to compensate.
Geo-stationary means stationary to one point on the earth.
Geo-synchronous means in synchronization to the earth. This one only means that the satellite will be above the same place once a day.

Geo-stationary is about 22000 miles up, or travel a circumference of (4000+22000)*2*pi = ~165000 or around 6800mph.


That might come to mind when you're thinking communication satellites, but these are not directional in the same manner as having to direct the signal toward them. You lock on to whatever satellite is passing, and the signal will be passed from sat to sat as they pass (like travelling past cell towers)
GPS is kind of the same thing.
I missed this post earlier (I was posting at the same time).

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

Larry Jacks
2009-Feb-12, 06:54 PM
<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 (http://ccar.colorado.edu/asen5050/projects/projects_2000/redlin/) 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.

Argos
2009-Feb-12, 07:11 PM
Not necessarily. Consider the case of a satellite constellation like Iridium (http://ccar.colorado.edu/asen5050/projects/projects_2000/redlin/) 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.

geonuc
2009-Feb-12, 07:31 PM
Not necessarily. Consider the case of a satellite constellation like Iridium (http://ccar.colorado.edu/asen5050/projects/projects_2000/redlin/) 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.
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.

mugaliens
2009-Feb-12, 07:54 PM
The satellites were high enough that many pieces will be up there for decades, perhaps as long as a century. The Iridium is in a near polar orbit. That means the pieces will sweep across many other orbits, increasing the chances of further collisions. This most definitely is not good.

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

Gsquare
2009-Feb-13, 07:02 PM
I wonder if several more collisions happen as a result of this one, the chances for a runaway stream of collisions.

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

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

Nicolas
2009-Feb-13, 07:17 PM
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. ;)

pumpkinpie
2009-Feb-13, 07:34 PM
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



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


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.

Disinfo Agent
2009-Feb-13, 09:30 PM
Nasa alert as Russian and US satellites crash in space (http://www.guardian.co.uk/world/2009/feb/12/nasa-alert-as-satellites-collide):


In the past abandoned or dysfunctional satellites have caused problems, with some pushed into extremely wide "graveyard" orbits that move them out of the way of other spacecraft. In several cases, rogue satellites have been shot out of the sky to prevent them crashing to Earth.Dysfunctional satellites? Do they come from broken homes? :eh:

NEOWatcher
2009-Feb-13, 09:35 PM
Dysfunctional satellites? Do they come from broken homes? :eh:
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.

Gsquare
2009-Feb-13, 10:46 PM
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. ;)

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/corporate/mediaCenter/news/iridium-cosmos/GaussianDebris_BreakUp_3hrs.jpg


G^2 :D

Warren Platts
2009-Feb-13, 11:50 PM
Has it occurred to anyone that this might not be an accident? It happened over Siberia. . . .

Gsquare
2009-Feb-14, 12:07 AM
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".

crosscountry
2009-Feb-14, 10:07 PM
They went as far as excusing Iridium, but didn't go as far as putting blame on the Russians either. It still infers no-fault.
But; the natural tendency of a conclusion will be to blame the derelict. In reality, the only way to blame someone is if the non-derelict could have maneuvered to avoid it. I doubt that would be a common case, but it would be the tracking authority itself that is to blame.


That doesn't even show the higher orbits. Look at the one on the wiki page for space debris (http://en.wikipedia.org/wiki/File:Debris-GEO1280.jpg). Not as good resolution though.


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.

crosscountry
2009-Feb-14, 10:08 PM
Has it occurred to anyone that this might not be an accident? It happened over Siberia. . . .

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

Warren Platts
2009-Feb-14, 11:29 PM
Iridium satellites are hardly worth destroying. Maybe you're suggesting we did it on purpose? The Russian satellite wasn't even functional.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: (http://www.newscientist.com/article/dn16592-satellite-crash-prediction-is-plagued-with-uncertainty.html)


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! :o)

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

crosscountry
2009-Feb-15, 05:42 AM
you need to take this to another forum. I think Conspiracy theories would be more appropriate.

WalrusLike
2009-Feb-15, 09:36 AM
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.

Damburger
2009-Feb-16, 05:16 PM
you need to take this to another forum. I think Conspiracy theories would be more appropriate.

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.

Larry Jacks
2009-Feb-16, 07:36 PM
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 (http://www.obsat.com/images/Ir33coll_top.gif) 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.

peteshimmon
2009-Feb-16, 09:13 PM
Is this story connected with the stuff seen
falling in Texas yesterday?

Larry Jacks
2009-Feb-16, 10:03 PM
Not according to US Strategic Command (http://www.cnn.com/2009/US/02/16/texas.sky.debris/index.html).

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.

BetaDust
2009-Feb-16, 10:09 PM
Is this story connected with the stuff seen
falling in Texas yesterday?

Well, the BA doesn't think so.

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


"Watching it again makes it even more clear to me that this was an asteroid fragment a meter or so across (probably less) and not part of the debris cloud from the satellites. It’s simply moving too quickly."


--Dennis

Scamp
2009-Feb-16, 10:26 PM
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. :lol:

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

peteshimmon
2009-Feb-16, 10:33 PM
Just caught something on the news about a
meteor as big as a van. Looking forward to
the finders photos.

BetaDust
2009-Feb-16, 10:48 PM
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. :lol:

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


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

Larry Jacks
2009-Feb-16, 11:02 PM
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.

xzhgj287
2009-Feb-16, 11:21 PM
Judging from the graphic I linked above, the collision happened outside of Space Surveillance Network (SSN) sensor coverage.

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

Scamp
2009-Feb-17, 01:51 AM
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.

Thanks for the details, One always has a hollywood view of these things in mind where everything is monitored in real time with really nifty looking graphics.....

JonClarke
2009-Feb-17, 11:28 AM
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. :lol:

They have done much better than that. Of the seven Russian spacecraft to reach Mars, both flybys were successful, and four out of five orbiters sucessfully achieved orbit. Of four landers three entered the atmosphere as designed. It is only the actual entry and landing that proved problematic.

JonClarke
2009-Feb-17, 11:30 AM
Seeing this as deliberate requires a conspiratorial mind set as nutty as the more extreme 11-9 kooks. Let's keep such paranoid nonsense elsewhere.

Larry Jacks
2009-Feb-17, 02:20 PM
Strela-3 (http://www.astronautix.com/craft/strela3.htm) satellites use gravity gradient stabilization. That's a weak form of stabilization good enough to maintain mission orientation but not good enough for precision maneuvers. The Strela-1 and Strela-2 satellite systems didn't even have propulsion systems and it's quite possible Strela-3 didn't have one, either. A propulsion system simply isn't necessary for every mission and store/dump communications often didn't require it.

I'll try to check some of my OA contacts to see if a maneuver has ever been detected with this type of satellite. They maintain a history of all element sets produced from the time a satellite is first cataloged until it decays.

The fact that these satellites were designed to only operate for a couple years rules very strongly against your speculation that the collision was in any way intentional. It isn't hard to determine when a communications satellite dies - it stops radiating RF energy. The debris cloud from this collision affects Russian satellites at least as badly as anyone else's satellites.

tusenfem
2009-Feb-17, 03:00 PM
Warren Platts if you think there is a conspiracy regarding this satellite collision, then please open your own thread in the conspiracy theories section of this board.
The same holds for Gsquared (although you might be just making fun).

Larry Jacks
2009-Feb-17, 07:26 PM
The only mystery is why this collision wasn't predicted and the orbit of the Iridium satellite tweaked well in advance.

I just attended a meeting where I learned that some 500-700 close approaches (defined as two objects in space passing within 1 KM of each other) happen every day. The calculated position of any space object has an associated margin of error that depends on many factors. For example, dead satellites, space debris, spent rocket bodies, etc. aren't tracked as often as other objects because their orbits tend to be stable. In addition, each conjunction assessment has a margin of error. Apparently, this conjunction was predicted but due to the margin of error, it wasn't even assessed as the biggest collision risk for that day. Such is the mathematics of conjunction assessment.

As to tweaking the Iridium satellite's orbit, a delta-v of 1 cm/sec executed as little as 1 rev before impact would've caused them to miss each other. However, because the impact risk between these two objects wasn't deemed high, no maneuver was made. The margin of error inherent to conjunction assessment and the "big space, little me" mindset probably means they wouldn't have maneuvered anyway. There is no mathematically valid means of stating that they will definitely impact, just that there is a certain probability that the objects will pass within a certain distance of each other.

Warren Platts
2009-Feb-17, 07:34 PM
Well, that, and the risk if they did do that 1 cm s-1 nudge, and the collision still occurred, boy, someone would really have some explaining to do. . . . :(

Meanwhile, have you been able to find any evidence that Cosmos satellites have exhibited signs of at least minimal maneuverability in the past?

Larry Jacks
2009-Feb-17, 08:39 PM
I talked to an individual OA this morning but she said she couldn't recall whether they maneuvered or not. Like I said before, the satellite was gravity gradient stabilized (http://en.wikipedia.org/wiki/Gravity_gradient). That technique keeps one side of the satellite facing the Earth but generally doesn't provide the pointing accuracy in other attitudes to orient thrusters (http://books.google.com/books?id=uTwb7d8PTXMC&pg=PA300&lpg=PA300&dq=%2B%22gravity+gradient%22+%2Bstabilization+%2Bp ropulsion&source=bl&ots=EAMXILnkU9&sig=PhmN9OGBbhZqhXIWzmhXWbfkA58&hl=en&ei=Xh2bSfyeApa5twfGoai9Cw&sa=X&oi=book_result&resnum=6&ct=result#PPA302,M1).

Gravity gradient stabilization, although feasible, is limited because of the weakness of the gravity-gradient torque. Thus it cannot be used at very high altitudes, where this torque is very weak, and it cannot be used at very low alttitudes, where it will be overwhelmed by aerodynamic torques. Also, because the gravity-gradient torque is so weak, attitude control by this means cannot be very precise. In general, it is difficult to achieve stability to better than a few degrees by gravity-gradient techniques alone. Also, the mission requirements of the spacecraft may not be consistent with the mass distribution required for gravity-gradient stabilization. This can be overcome by attaching a proof mass, typically around 1 kg, at the end of a long boom, which tends to increase the size of the other moments of inertia relative to the moment about the vertical, which for gravity-gradient stabilization must be the smallest. This is illustrated in figure 5.28, which depicts a typical gravity-gradient stabilized spacecraft. The long boom, however, may have significant flexure modes, typically of low frequency, which can couple to the attitude motion of the base module of the satellite. These flexure modes can be attenuated by the use of momentum dampers (see section 5.8.6), but the remaining oscillation still leads to a degradation in control performance. Furthermore, due to the variations in the orbit radius, can lead to a destabilizing torque. These effects limit the usefulness of gravity-gradient stabilization for spacecraft with tight control requirements.

(Note: I couldn't cut-n-paste from the document so I retyped the paragraph - any typos are my own).

As far as I can determine, that version of the satellite lacks any propulsion system the same as the two earlier versions.

You can read more than you've probably ever cared to know about gravity gradient stabilization here (http://www.aoe.vt.edu/~cdhall/courses/aoe4140/SatDy.pdf).

Warren Platts
2009-Feb-18, 11:11 AM
Then there is the purported negative decay. I don't know how to interpret TLE's myself, unfortunately, so I can't check that fact.

Actually I just found this from space.com (http://news.yahoo.com/s/space/20090217/sc_space/satellitecrashwhostoblame):


Nick Johnson, an orbital debris expert with NASA's Johnson Space Center . . .

According to Johnson, Cosmos 2251 drifted down from a higher orbit to the Iridium satellite's altitude. Doesn't sound like negative decay to me.

ETA: Here's the TLE for Cosmos 2251 (http://www.n2yo.com/satellite/?s=22675)

1 22675U 93036A 09048.32316889 .00000244 00000-0 10000-3 0 7558
2 22675 074.0409 005.1768 0024861 146.6264 213.6424 14.32046731818533
I have no idea how to interpret it, though.

Larry Jacks
2009-Feb-18, 02:05 PM
First, a correction on my part. I found out yesterday that Cosmos 2251 wasn't a Strela 3 but was a Strela-2m (http://www.astronautix.com/craft/strela2m.htm). The Strela-2M is a larger store/dump communications satellite than the Strela 1 or Strela 3 but it still used gravity-gradient stabilization. From everything I've been able to find and to recall, it has no propulsion system.

A TLE follows a specified format as explained here (http://www.mindspring.com/~n2wwd/html/body_tle_format.html). To know how the satellite was trending, you'd need an older TLE (say from a year ago) to compare to this one. This TLE simply states the parameters for the orbit as of the epoch date when it was calculated.

Line 1:
22675U - 22675 is the Space Control Center catalog number. The U is for unclassified.
93036A - This is the international designator (1993 launch date, 36th launch of the year, A is the piece designator (some launches result in several pieces being cataloged)
09048.32316889 - Epoch date (2009, 48th day of the year [Feb 17th), and fractional part of day when the elset was calculated (~0745 Zulu)
.00000244 - NDot drag parameter (used by propagator), the rate of change in the number of orbits per day
00000-0 - NDotDot parameter - rate of acceleration in the number of orbits per day (this looks like a very stable orbit)
10000-3 - BStar drag parameter used by propagator
0 - Ephemeris type - uses SGP propagator
7558 - Element Set Number assigned sequentially (up to a 4-digit integer from 1 to 9999). This elset has been updated 7557 times (or more) since it was first cataloged.

Line 2:
22675 - SCC catalog number
074.0409 - orbit inclination in degrees
005.1768 - right ascension of the ascending node
0024861 - Orbital Eccentricity -- there is an implied leading decimal point (between 0.0 and 1.0) = 0.0024861 (near circular orbit)
146.6264 - Argument of Perigee
213.6424 - Mean Anomaly
14.3204... - Mean Motion (revolutions per day) also means the orbital period is 100.55 minutes. Fairly high orbit.

Gigabyte
2009-Feb-18, 03:11 PM
I don't care what caused it, it seems like a bad thing.

Warren Platts
2009-Feb-18, 08:17 PM
First, a correction on my part. I found out yesterday that Cosmos 2251 wasn't a Strela 3 but was a Strela-2m (http://www.astronautix.com/craft/strela2m.htm). The Strela-2M is a larger store/dump communications satellite than the Strela 1 or Strela 3 but it still used gravity-gradient stabilization. From everything I've been able to find and to recall, it has no propulsion system.

A TLE follows a specified format as explained here (http://www.mindspring.com/~n2wwd/html/body_tle_format.html). To know how the satellite was trending, you'd need an older TLE (say from a year ago) to compare to this one. This TLE simply states the parameters for the orbit as of the epoch date when it was calculated.
Wow! Thanks for the explanation of TLE's Larry! That's awesome! As for the Strela-2M, the astronautix link says that the Strela (which means "arrow" in Russian :o) did possess some sort of "guidance system". Also, they got the picture wrong. I found some pictures of the Strela-2M (http://www.novosti-kosmonavtiki.ru/content/photogallery/gallery_054/pages/IMG_9003.html) and there are no thrusters that are obvious. Still I can't find a definitive source that says that Strela-2M's were totally incapable of maneuver. Also what else could explain the 24-36 month rated lifetime if it's not because they tended to run out of maneuvering fuel? They weren't nuclear powered (it was powered by solar panels), and so it seems that they must run out of something.

Then there's the little matter of the "negative decay". It turns out that Johnson was wrong or lied: Cosmos 2251 was below Iridium 33 and was gaining altitude somehow. So I'm not convinced yet that the collision could not possibly have been on purpose. So I went ahead and started a new CT thread (http://www.bautforum.com/conspiracy-theories/84930-iridium-33-cosmos-2251-collision-not-accident.html) like tusenfem asked.

Larry Jacks
2009-Feb-18, 09:00 PM
Those are some excellent pictures. Thanks for the link. That photo on the Astronautix site is labeled as a Strela 1. The Strela 1 & 3 were known as "Multiple Payload Communications System" (MPCS). IIRC, the 1s were launched 8 at a time and the 3s were launched 6 at a time. The Strela 2Ms were known as Single Payload Communications Systems (or satellite) (SPCS) and launched individually.

As for the lifetime, these satellites were all designed during the old Soviet era. They build satellites in large numbers and made them cheap. It didn't matter if the satellites didn't last long if you build them (and boosters) in large enough numbers to maintain the desired constellations. For example, their first generation of Glonass (http://en.wikipedia.org/wiki/GLONASS) satellites (their version of GPS) only lasted about 16 months. With a full constellation of satellites, they'd be launching replacements (3 at a time on Proton boosters) every couple months just to replace the failures. It took them a long time to learn how to last for several years. Their reliability has improved dramatically since the 1980s.

SPCS satellites didn't last that long because the electronics failed. Everything I can recall about MPCS and SPCS satellites indicate there was no propulsion system at all. They were launched into high stable orbits so there was no need to maneuver.

tusenfem
2009-Feb-19, 09:52 AM
I have moved two of Warren Platt's posts to the conspiracy theories thread, which you can find here (http://www.bautforum.com/conspiracy-theories/84930-iridium-33-cosmos-2251-collision-not-accident.html) (as requested by WP in that thread).