U.S. satellite gonna come down on Earth in...somewhere...
So you may be wondering how often this happens...and that depends on what you mean by "often". Tim the Rocket Scientist and any other satellite experts - please correct me if I'm wrong on this thread as satellites are not my forte...
Most satellites go through a deorbit, burn-up, and dunk in the ocean. I don't really have a number, but I think it's in the 10-25 per year range.
Most are controlled trajectories, some are not controlled, but they the trajectory has been safely set. However, this seem to be a case where the de-orbit trajectory has not been and it won't be a controlled either - this can be dangerous. Calculations on the landing area accurate to up to +/-1000miles - that's why aiming to "land" the satellite in a huge uninhabited part of Earth, like an ocean, is attractive.
There are some clever ideas for deorbit "bolt-on" modules: http://www.tethers.com/papers/SmallSat_nanoTerminator.pdf
Also, the Hubble Space Telescope is expected to be deorbited by a "bolt-on" de-orbit module that is expected to automatically mate to the telescope and safely deorbit.
As far as why they forced to deorbit - a few major reasons: if they have become or are at risk of becoming less than flight-worthy, if they are simply too expensive to maintain/operate, and/or if they are not useful enough to use (even as a back-up).
So...how paranoid should you be considering the satellite has some nasty, toxic hydrazine? Well, not really any because many, many people and organizations will be calculating where the impact area is and considering ~2/3rds of Earth is covered by water - probably not gonna hit land. But I'm sure information about both hydrazine and impact location will be forthcoming in the next couple weeks.
U.S. to use missile to shoot down satellite
Feb. 14: Vice Chairman of the Joint Chiefs of Staff, Gen. Jim Cartwright talks about how the U.S. will attempt to shoot down a broken U.S. spy satellite.
Video, ~4min: http://www.msnbc.msn.com/id/21134540/vp/23170000#23170000
transcript of 2/20 DoD background briefing on shoot-down...
controversy surrounds purpose behind satellite shoot-down...
...who knows! ya know? I mean...
All I gotta say is that I'm pretty disappointed that there's gonna be more debris up there.
First, We need the target practice. Our military has a job to do and this lets them practice it. Should the need ever arise.
Second, if you shoot it at the right time you can control the fall, or at least break it up into smaller pieces that don't cause as much harm or burn up.
Third (I lied about two) if they blow up the tank of nasty stuff it also burns up or dissapates on the way in. Ok this is really related to #2.
Yeah, I can understand the issue of practicing it - and who knows whether this is a genuine coincidence or a convenient cover...
I just haven't heard/read that a safe deorbit and burn-up is the end-goal - I've just heard/read that the end goal is to eliminate or drastically reduce the implications of hydrazine coming down on people and we'll just have to deal with more space debris. If you know of something that says a re-entry burn-up is a top tier objective after addressing the hydrazine, lemme know 'cause I guess I missed it.
Too bad and automated deorbit module isn't available, that'd help out a lot in both verifying new launch and guidance systems as well as reducing space debris. There was a program that tested a portion of such a system a few years ago, but I dunno what, if anything is going on with it now:
*Disclaimer: Shalin is not a missle expert, Shalin is not a satellite expert, Shalin is not an anti-satellite missile expert either...but Shalin does know some aerospace stuff that maybe helpful to understand regarding the shoot-down of the wayward satellite...
Although they haven't had as much use or testing as conventional weapons, Anti-Satellite (ASAT) weapons are not new - they've been around for decades. The last known test the US performed were in the 80's. ASAT weapons were basically conceived as strategic solutions to threats (use of space as a battleground) during the Cold War.
As far as why 3 are being fired - 1 as a first shot and 2 "second chances" seems the likely logic to me. Guidance systems are more sophisticated these days, so I would actually expect the first shot to be successful.
I don't think they'll be fired all at once. If they don't hit the target, they'll likely be directed back through the atmosphere to burn up, self destruct, or both.
I've said it before and I'll say it again - it's disappointing to me that this shoot-down is going forward 'cause it'll just create more debris up there that isn't really helpful.
Hey, the last US satellite landed in good ol' Australia, in southern WA (Western Australia, not Washington).
Fortunately the clean up from the debris of SkyLab was paid for, as the US government was slapped with a AU$400 for littering by the local council. Kinda funny I think...
Why? Because the Pacific Ocean is an easy target to "hit"
There is a moral issues here: Most people in the world lives on land and therefore value land more than water. So "we" don't mind "hitting" water - as long as it's not close to anything valuable man-made (cruise ships, coastal towns, etc.) or hard to get to resource (fossil fuels, etc.)
But this is simply the best (or least bad, depending on your view) that there is for ensuring public safety. Part "what do we value and how do we avoid it" and part statistical probability of carrying out the deorbit/re-entry.
BTW - You live in Hawaii! That's awesome! ...I'm sure you get that a lot, but seriously - must be nice, yes? Maybe the BOL cruise will come out there and we'll all go out for walks on the beach, surfing, and all the good food, scenery, culture, and wildlife we can stand...yes, I look forward to that
hmm...it might hit "land in the ocean"...8th continent...
i think that the according to the news which is the satellite will hit until two hours before it enters the Earth's atmosphere, moving at 5 miles per second.
What are your chances of being hit by debris from it? About one in 21 trillion, NASA said. When you add up the 7 billion people now alive, the chances that someone, somewhere on the planet could get hit are 1 in 3,200.
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