[bratticus]

Scientists aware satellite paths would be close

By Tim Hepher

PARIS (Reuters) - European space scientists were aware of the potential for a close encounter between Russian and U.S. satellites before they crashed.

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"It is not a case of two satellites coming together out of nowhere; they had been followed. The U.S. catalogues can give an alert but these are not necessarily completely exact."

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An Iridium spokeswoman did not say whether it had been warned but said the firm always monitors its satellites closely.

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[Plantagenet]

NASA and the US defense department track EVERYTHING in space so the shuttle and valuable US satellites can be moved out of the way well in advance if there is a possibility of a collision.

Why wasn't the Iridium satellite moved?

Because it wasn't in any danger until the Russians activated their military satellite and slammed it into the US Iridium satellite.

The cover story of an "accidental" collision is completely ridiculous......

[AgentR]

Basically, they knew that a collision was within the margin of error.
They decided that the risk vs cost was acceptable.

Sometimes... the low probability expensive event happens.
Thats why you have insurance.

Do you go to the expense of changing the orbit of a satellite every time a collision is possible? What if only 1 in 10 would result in an impact? What if only 1 in 10,000 would result in an impact?

[Tanada]

Basically, they knew that a collision was within the margin of error.
They decided that the risk vs cost was acceptable.

Sometimes... the low probability expensive event happens.
Thats why you have insurance.

Do you go to the expense of changing the orbit of a satellite every time a collision is possible? What if only 1 in 10 would result in an impact? What if only 1 in 10,000 would result in an impact?

Not to mention the fact that LEO is getting filled with all sorts of debris from objects like the dead russian sat in this collision down to paint flakes off of equipment launched into LEO. Collisions will keep happening until someone bites the bullet and start delibrately knocking down a lot of the debris to clean up the area. Probably cheaper for now to just keep buying insurance.

[Plantagenet]

Do you go to the expense of changing the orbit of a satellite every time a collision is possible? What if only 1 in 10 would result in an impact? What if only 1 in 10,000 would result in an impact?

Of course you move the satellite every time a collision is possible. Satellites are very expensive, and the expense of building another satellite and relaunching it is far greater then the minimal expense of moving it.

Orbital mechanics are very well understood. The people at NASA constantly track every satellite in space and they know the location of [u]every satellite up there to within a centimeter at all times[/u] --- if forward calculations of the satellite travel paths show there is any chance of a collision they move the US satellite.

Only the Russian satellite wasn't where the calculations showed it would be.....IMHO the Russians intentionally moved it into the path of Iridium satellite and then intercepted and destroyed the Iridium satellite.

[evilgenius]

The Russians were testing their capabilities. They need to know that it still works in case they have to use it in the near future.

[AgentR]

satellite up there to within a centimeter at all times.

Please provide a link to an official claiming such a degree of accuracy.

[Ferretlover]

Well! That's one Russian satellite down, how many to go?

[Plantagenet]

satellite up there to within a centimeter at all times.

Please provide a link to an official claiming such a degree of accuracy.

No problemo.

From the US patent #6016117 for satellite positioning:

"Specifically, the ephemeris for a given satellite comprises:

a) The square-root of the semi-major orbital axis, which is half the greatest dimension of the elliptical orbit. The square-root ranges from 0 to about 8192 square-root-meters, corresponding to a semi-major axis a of about 67 megameters, with a resolution corresponding to about 20 millimeters for the typical orbit that has a semi-major axis of 26560 kilometers. Transmission of the square-root rather than the semi-major axis itself allows calculation of the mean motion n0, which is the average orbital angular velocity, without using a square-root operation:



n0 =(μ/a3)0.5 =μ0.5 /(a0.5)3

where μ is the earth's gravitational parameter, commonly the WGS-84 value of 398600.5 kilometers-cubed-per-second-squared. The value of n0 is typically 146 microradians-per-second, corresponding to about 3874 meters-per-second.

b) The ephemeris reference time of the week T0, which is the time from the beginning of the current GPS week to a time near the middle of the time interval for which the ephemeris is valid. The reference time T0 is an integer multiple of 16 seconds. Time T0 is commonly subtracted from the given time of interest T to get ephemeris time t, that is, time referred to the ephemeris's epoch:

t=T-T0

c) The mean-motion difference ∆n, which is a correction to the mean motion no as computed above:

n=n0 ∆n

The range of ∆n corresponds to about ±311 millimeters-per-second with a resolution of about 9.5 micrometers-per-second for a typical orbit.

d) The reference-time mean anomaly M0, which is the angle of the satellite at the reference time T0 from perigee which would result from uniform angular motion. Perigee is the point in the orbit closest to the earth. The resolution of M0 corresponds to about 39 millimeters for a typical orbit. M0 is used to find the satellite's mean anomaly M at ephemeris time t:

M=M0 nt

e) The orbital eccentricity e, which is the fraction of the semi-major axis by which the earth is distant from the orbital center. The dimensionless fraction e ranges from 0 to 0.03 with a resolution corresponding to about 3 millimeters for a typical orbit. Kepler's equation relates mean anomaly M to eccentric anomaly E, which is the actual at the reference time T0 about the orbital center from perigee to the satellite:

M=E-e sin E

Kepler's equation is commonly solved iteratively to get eccentric anomaly E from mean anomaly M. True anomaly v, which is the actual angle about the earth's center from perigee to the satellite, is commonly calculated from eccentric anomaly E by any of various formulas, for example: ##EQU1##

f) The argument of perigee ω, which is the angle about the earth's center from the ascending node to perigee. The ascending node is the intersection of the orbit with the plane of the equator at which the satellite passes from the southern to the northern hemisphere. The resolution of ω corresponds to about 39 millimeters for a typical orbit. The argument of perigee ω is commonly added to the true anomaly v to get the uncorrected argument of latitude Φ, which is the angle about the earth's center from the ascending node to the satellite:

Φ=ω+v

g) The second-harmonic correction coefficients Cuc and Cus to the argument of latitude Φ. The ranges of Cuc and Cus correspond to about ±1621 meters with a resolution of about 49 millimeters for a typical orbit. They multiply the cosine and sine respectively of twice the uncorrected argument of latitude Φ to correct the argument of latitude u:

u=Φ+Cus cos 2Φ+Cus sin 2Φ

h) The second-harmonic correction coefficients Crc and Crs to the radius r. The ranges of Crc and Crs are about ±1024 meters with a resolution of about 31 millimeters. They multiply the cosine and sine respectively of twice the uncorrected argument of latitude Φ to correct the radius r:

r=a(1-e cos E)+Crc cos 2Φ+Crs sin 2Φ

The argument of latitude u and the radius r are commonly combined to calculate the satellite's position in the orbital plane (x',y'):

x'=r cos u

y'=r sin u

i) The orbital inclination i0 at the reference time, which is the angle that the orbital plane makes with the plane of the equator, typically about 55 degrees. The resolution of i0 corresponds to about 39 millimeters for a typical orbit.

j) The rate of orbital inclination i. The range of i corresponds to ±155 millimeters-per-second with a resolution of about 9.5 micrometers-per-second for a typical orbit.

k) The second-harmonic correction coefficients Cic and Cis to the inclination i. The ranges of Cic and Cis correspond to about ±1621 meters with a resolution of about 49 millimeters for a typical orbit. They multiply the cosine and sine respectively of twice the uncorrected argument of latitude Φ to correct the inclination i:

i=i0 +it+Cuc cos 2Φ+Cus sin 2Φ

l) The right ascension of the ascending node at the reference time Ω0, which is the angle measured eastward from the vernal equinox to the ascending node. The resolution of Ω0 corresponds to about 39 millimeters for a typical orbit.

l) The rate of right ascension Ω. The range corresponds to about ±80 meters-per-second with a resolution of about 9.5 micrometers-per-second for a typical orbit. Ω0 and Ω are commonly combined with Ωe, the WGS-84 earth's rotation rate, to calculate the ascending node's longitude:

Ω=Ω0 Ωt-Ωe T

The ascending node's longitude Ω and the inclination i are commonly combined with the satellite's position in the orbital plane to get the satellite's position in earth-centered earth-fixed coordinates (x, y, z)."


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This 9-year-old patent describes how satellite positions in 3d space can be determined to within 30-40 mm, and the velocity is known to within a few micrometers per second (thats velocity to within a millionth of meter per second).

When combined, these factors allow the determination of a satellite's position at all times on centimeter scales.

(---NOTE: the patent I quote above is 9 years old and PUBLIC....much better resolution can be obtained by the secret military satellite tracking systems---they are secret, but since they are better then the public systems, one might guess they are accurate to the millimeter or even sub millimeter scale.)

The bottom line is that the US (and Russia) knew EXACTLY where both these satellites were in their orbits at all times. The US didn't move the Iridium satellite because it wasn't in danger of colliding with the Russian satellite based on the centimeter-scale positions calculated for their conventional orbits.

Its impossible for them to have collided accidently. Clearly the Russians activated their military satellite and moved it to collide with the US Iridium satellite.

[AgentR]

Nice dodge.

[AgentR]

Its impossible for them to have collided accidently. Clearly the Russians activated their military satellite and moved it to collide with the US Iridium satellite.

It should be noted that I am not saying the Russians didn't in fact do this; nor do I honestly care if they chose to use a US commercial satellite as target practice, though it does seem counter-intuitive, given that they could put up their own target equipped with their own sensors and get more and better information out of the test. An anti-satellite weapon isn't exactly cheap; to burn one on a target that would provide no useful terminal function seems odd.

I am however saying that I think people on this board are very inclined to accept the most outrageous possible answer as the most likely, and it shows in this particular instance. The least outrageous answer is that the known solution of both orbits created a substantial risk of collision and the owner of the satellite found the risk / cost analysis to favor no action.

The mid ground, that I find unlikely but reasonable is that the owner of the satellite screwed up, either misunderstanding the possibility, or failing to take action that would have been desired had the situation been understood. More than a few multi million dollar losses have occurred in space simply as the result of some operator or engineer screwing up.

[Tanada]

I think people on this forum give way to little credit to human beings abillity to screw up regularly or even often. I htink it is just as likely that Irridium did move their orbit but someone goofed and they moved it in the wrong direction, ensuring a collision instead of ensuring a miss. Russia claims their sat was dead and naturally decaying in orbit, if they suddenly changed orbit with it to knock down the Iridium sat then the USAF and NASA both know it for certain and it is extremely likely that ESA and China also know it. Someone will spill the beans if that was what happenned to gain pollitical advantage over Russia. Does anyone besides me remeber when NASA slammed a probe into Mars at high speed because the braking rocket system was set to activate at a distance of X kilometers but the person doing the calculation used Miles? The braking rockets ignited at 62% of the distance needed for a successful entry into Mars and WHAM, too little too late. People screw up all the time, beleive it.

[Plantagenet]

Its impossible for them to have collided accidently. Clearly the Russians activated their military satellite and moved it to collide with the US Iridium satellite.

It should be noted that I am not saying the Russians didn't in fact do this; nor do I honestly care if they chose to use a US commercial satellite as target practice, though it does seem counter-intuitive, given that they could put up their own target equipped with their own sensors and get more and better information out of the test. An anti-satellite weapon isn't exactly cheap; to burn one on a target that would provide no useful terminal function seems odd.

Its odd....and its downright unfriendly. IMHO, just as Biden predicted a month ago, the Russians caused the collision to test the new administration and see how they respond to a provocation.

The mid ground, that I find unlikely but reasonable is that the owner of the satellite screwed up, either misunderstanding the possibility, or failing to take action that would have been desired had the situation been understood. More than a few multi million dollar losses have occurred in space simply as the result of some operator or engineer screwing up.

Well, except the protocols for satellite safety are all automatic and pre-arranged so there is no chance of a misunderstanding or screwup. The orbits for all earth-rotating objects are calculated months in advance and all re-checked and updated regularly. Any close-encounters are determined automatically by computer and any close encounters are automatically flagged by the computers doing the calculations. A very close enounter would trigger bells and alarms months in advance. There are protocols for satellites that must be followed when any potential close encounters are predicted....the collisions are ALWAYS avoided by moving the US satellite. There is no decision to be made....its all pre-decided with large safety factors built in.

The US knew precisely where the Russian military satellite was supposed to be....but the Russians moved it into the path of the US satellite and caused the collision. I don't agree with your suggestion above that the Russians did this to test their system. I think the Russians did it to test the character of the new US administration.

[Tanada]

Here is an IMO better report on the collision from a space advocacy group I frequent. Not sure why it took me so long to think to post it here, it just did. http://spaceflightnow.com/news/n0902/11iridium/

"There are two issues: the immediate threat and a longer-term threat," he said. "It turns out, when you have a collision like this the debris is thrown very energetically both to higher orbits and to lower orbits. So there are actually debris from this event which we believe are going through the space station's altitude already. Most of it is not, most of it is still clustered up where the event took place. But a small number are going through station's altitude.

"Yesterday, we did an assessment of what the risk might be to station and we found it's going to be very, very small. As time goes on, those debris will (come down) some over months, most over years and decades and as the big ones come down they'll be tracked, we'll see them and the worst-case scenario, we'll just dodge them if we have to. It's the small things you can't see are the ones that can do you harm."

Asked if other satellites might be at risk, Johnson said "technically, yes. What we're doing now is trying to quantify that risk. That's a work in progress. It's only been 24 hours. We put first things first, which is station and preparing for the next shuttle mission."

Russia has much if not more to lose by any damage to ISSA so assuming this was a hostile act is incorrect. It would be the same thing as China dumping the dollar, most knowledgable people say they have too much to lose by doing it.

[Plantagenet]

"Yesterday, we did an assessment of what the risk might be to station and we found it's going to be very, very small.

Russia has much if not more to lose by any damage to ISSA so assuming this was a hostile act is incorrect.

The Russian satellite didn't come anywhere near the ISSA---it hit an Iridium satellite. Taking out the Iridium satellite posed essentially no risk of damage to the ISSA so it is illogical to argue that the Russians wouldn't take out the Iridium because it would damage the ISSA.

[Plantagenet]

"A private Web site, named Socrates, does give daily risk of crash warnings for satellites and Iridium, with 65 satellites, frequently is in the top 10 daily risks, Johnson said. However, the Iridium satellite wasn't on Tuesday's warning list, he said."

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In other words....the database of highly accurate satellite orbits kept by Socrates shows the Russian satellite wasn't even going to come close enough to Iridium to trigger a warning........unless that orbit was changed.

Pick 'em.....Little green men, Dr. Evil or the Russians must have changed the orbit of the Russian satellite to intercept the US satellite.

[AgentR]

In other words....the database of highly accurate satellite orbits kept by Socrates shows the Russian satellite wasn't even going to come close enough to Iridium to trigger a warning.

Yeah.. we'll trust a internet web database of satellite orbits because an internet poster says they are highly accurate. When in fact there is very little, if any way to verify the quality of the information they might provide.

If given the choice between an international act of war, or a web site screwing up...

I think I'd have to put money on the web site screwing up.

Let me ask you this, does this website warrant that its information can be used for legal, navigational purposes? Does it assert that its information is complete and accurate, or does it disclaim liability for any use other than informational and statistical purposes?

[Kristen]

The Russians would be declaring war on Iridium, not the U.S.. It was an accident.

[Plantagenet]

The "accident" theory suggests that (1) either no one could predict the collision or (2) that those in charge of modelling satellite orbits somehow "missed" this collsion.

But (1) mathematical models and satellite tracking can predict orbital paths to centimeter-scales. That means Its impossible for large satellites to suddenly "accidentally" collide without warning.

That leaves the possiblity that those responsible just "missed" the data showing this collision was going to occur.

But there are multiple agencies around the world filled with scientists and engineers whose job is to track the satellites and model their orbits.......I count at least five....The US has NASA and the Defence Department, the Russians have their own space tracking system, the EU also has a space tracking agency, and then there is Socrates, the private system.

So all five had to ignore their own computer models predicting this collision at the same time for this to be an accident.

IMHO, its highly unlikely that all five had engineers who suddenly became lazy and who simultaneously didn't do their job of checking the satellite orbit models for weeks and months and years ahead of the collision, and who all ignored the automated warnings such models automatically produce.... (NOTE THAT Socrates has already double-checked and they say their models show the two satellites shouldn't even have been close to one-another).

[Tanada]

Tracking the 18,000+ objects in orbit around the planet is one thing, doing something about it is completely different. The Russian satellite was dead and had exhibited that dead behavior for years, when you have no propellant there isn't a darn thing you can do to shift your orbit for good or ill. All those tracking agencies you are talking about, only the USA and Russian ones had any reason to talk to each other about it and the USA ones had a responsibility to talk to Iridium because it is a USA based company. After doing their talking it was up to Iridium to command their sat to shift its orbit. Either Iridium didn't shift at all, they didn't shift enough, or they shifted the wrong direction.

You are also making the assumption that with 18,000 objects being tracked that the agencies tracking them have all the manpower they need to review every computer alert in a timely manner. Considering an orbit at that altitude is about 4 hours and Iridium alone has 66 objects in it, not to mention everyone else who wants the same resolution including every military that has satellites, weather satellites and others that particular volume of space has heavy traffic.

My understanding based on what I have read is that these two collided while traveling in roughly the same direction, if they had hit from opposing directions it would have been spectacular and the energy released would have vaporized a good portion of both objects. As is they were broken up into two major chunks plus some 600 fragments of more than 10 cm size. Now that debris cloud has added about 500 objects to the orbital space in question, some of the debris has already re-entered and more will in the next year but the majority is in trajectory/orbits with energy very similar to what it was before the collision because it was oblique, not head on or T bone. That means the orbital volume there is now horribly more crowded than before and debris impacts are now much more likely than before, which is going to be a PITA for the Russians, they like to park their spy sats in that orbit just like everyone else does.

What if it turns out the US government deliberately fed Iridium false data so that when they shifted orbit it caused the collision to deny that space to Russia? The USA is so proud of and confident in Predator/Stealth spying they may have decided that spy sats are old technology and this gave them a perfect opportunity for denial of access to a rival covertly.