Slashdot Mirror
Collided Satellite Debris Coming Down?
Jamie found this Bad Astronomy blog on the many reports beginning about 7 hours ago of one or more fireballs in the sky across Texas. That blog's proprietor first doubted that the phenomena could be due to the satellites that collided in orbit last week, but later left the possibility open. The National Weather Service for Jackson, KY put out an announcement about possible explosions and earthquakes across the area and blamed the defunct satellites. "These pieces of debris have been causing sonic booms...resulting in the vibrations being felt by some residents...as well as flashes of light across the sky. The cloud of debris is likely the result of the recent in orbit collision of two satellites on Tuesday...February 10th when Kosmos 2251 crashed into Iridium 33."
An Austin TV station has more reports.
As someone noted above, I'm now very sure this was a natural piece of cosmic debris, a chunk of asteroid or something similar. I posted a wrapup with my thoughts.
*** Phil Plait, aka The Bad Astronomer http://www.badastronomy.com
RTFA carefully. Citizens are reporting sounds and vibrations they -think- are earthquakes etc. but authorities are saying it is just caused by the sonic booms of stuff (whatever it is) entering the atmosphere and exploding.
Seismometers detect things like sonic booms and lightning strikes from quite large distances away.
So if it created a sonic boom coming down through the atmosphere it could have been detected as seismic activity.
Staying in orbit requires a the right velocity. The results of a collision will have different velocities and some of that will de-orbit.
Engineering is the art of compromise.
The FAA issued a Notice To Airmen yesterday predicting debris and asking pilots to report.
I think there may be some conflict between the FAA's safety concerns and NORAD's secrecy. NORAD will weigh in eventually (when they're sure what they can and can't say), but there no reason to throw away the FAA's opinion, even though they are not the "go to" agency.
That's far from the lowest LEO. The International Space Station (ISS) orbits at about 358km.
Well, we were warned...
ZOMBIES AHEAD!
LEO is between 160 and 2000 km.. therefore 600 is in the low end of LEO.
How we know is more important than what we know.
Giant subterranean worms moving through the bedrock, and they cover it up.
It's the only explanation.
This is not the funny you're looking for.
Getting hit by a meteorite is pretty unlikely. The only well documented case happened in 1954, and it only resulted in a bruise.
There are many times more natural meteorites than artificial ones, so it's unlikely that anyone will be hurt by space debris meteorites.
Gravity is a foreign concept to some.
I hate to break it to you, but I seem to recall that ol' Isaac had a lot to say about momentum as well. If it's going to come to believing your speculations as opposed to Newton and Einstein, well, you're going to lose every time, at least in my book.
The satellites were pretty much shredded into perhaps tens of thousands of little bits - and the bits and pieces are going to have a variety of orbits and velocities. I don't think I ever said that NONE of it could be deorbiting this quickly, just that it's very unlikely that very MUCH of it could be doing so, and that it requires a fair amount of debris to make a visible display. Moreover given that the pieces almost certainly don't all have exactly the same velocity, it's highly unlikely that very many of them would deorbit simultaneously.
Gravity is only part of the story.
Holding "Control" and "Shift" on the roadsign control panel while typing in "DIPY" will reset the sign to the default access password, "DOTS".
(Also posted to Bad Astronomy.)
A simple orbital analysis using the ground tracks from, e.g. Heavens-Above.com shows that this was not debris form the collision.
The debris from a collision keeps more or less the same orbit as before, but is spread out along the orbit. (Orbital plane changes require a lot more delta-v than changing the along-track position or altitude, since drift along the orbit accumulates, but displacements across the orbit swing back and forth with each cycle.)
Looking at the ground tracks of
Iridium 33 and
Cosmos 2251
Just eyeballing the tracks, the North-going leg of the orbit of Iridium 33 crosses the latitude of Texas at around 10 PM local time. For Cosmos 2251, it crosses about 4 PM local.
An 11 AM fireball could be Iridium debris, but only if it were heading to the south-south-east. The fireball was heading NNE. So this was NOT debris from either satellite.
Gravity is fighting against a hell of a lot of orbital momentum, so it takes time for these bits to fall. Also since the satellites were going the same way at roughly the same speed all the bits are going to go at roughly that speed and direction. Think of it as one rear ending the other. The big difference is instead of a few km/h difference in speed it might be closer to km/s.
I had the advantage of being taught undergraduate supersonic fluid flow and basic orbital mechanics by a guy that designed satellites and the early scamjets. Others know a lot more than I picked up in those few hours but we are not describing a terribly complex system here.
....here: http://www.chron.com/disp/story.mpl/front/6264797.html
Ceterum censeo Carthaginem delendam esse