So... giant satellite falling to Earth, and no one knows where?

[Starwhip]

Who's heard of the GOCE satellite falling to Earth on Sunday night/Monday morning? Apparently, it's impact area is unknown. Much fun will follow.

http://en.wikipedia.org/wiki/Gravity_Field_and_Steady-State_Ocean_Circulation_Explorer

http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE/Satellite

http://www.cnn.com/2013/11/07/world/satellite-falling/

[Kerbart]

Impact area is quite well known: earth's surface. And they narrowed it down to either land or ocean. As it will break up in reentry this will be a non-event anyway.

[K^2]

Apparently, it's impact area is unknown. Much fun will follow.

Oh, it's not nearly that bad. It used to be a Sun-synch, so its orbit is going to run roughly North-to-South, placing impact areas in narrow strips of land spaced about 7.5°. The area of possible impact zone is actually not that great, and that zone can be estimated rather well. Trouble is that the zone itself stretches to cover pretty much everywhere on Earth.

I can't find the exact parameters, but since it's a Sun-sync, it's probably a dawn/dusk runner, so wherever it falls, it will be dawn or dusk there. Just stay indoors at these times. I doubt shrapnel big enough to punch through the roof is going to survive reentry.

[Nibb31]

GOCE isn't exactly a "giant" satellite either. It's only 800kg, which is ligher than most small cars these days.

[StarGaming]

Yea but imagine that falling to earth at 2000+ m/s ;/ However It's so small that It will break up on re-entry. So nothing to see...Or worry about for that matter.

[Britpoint]

Bear in mind by the time whatever isn't completely incinerated during re-entry reaches the ground, it'll be travelling at a tiny fraction of that orbital velocity. Even if a surviving fragment bumped you square on the noggin it's pretty unlikely you'd have anything much worse than a headache.

[Scotius]

Bear in mind by the time whatever isn't completely incinerated during re-entry reaches the ground, it'll be travelling at a tiny fraction of that orbital velocity. Even if a surviving fragment bumped you square on the noggin it's pretty unlikely you'd have anything much worse than a headache.

Ouch. You might want to rethink that. Even couple of grams travelling at terminal velocity can and will really hurt you. Anyone who was caught by hailstorm in the open can attest to it.

[Tex_NL]

Chances of a piece of debris actually hitting a person are negligible to the extreme.

The damage a piece of debris can cause is only partially dependent on speed. We all know F= m*a, mass is just as much a factor as speed/acceleration. A penny at terminal velocity might cause some skin damage but a bowling ball traveling a few m/s can kill.

Edited November 10, 2013 by Tex_NL

[Seret]

Chances of a piece of debris actually hitting a person are negligible to the extreme.

The damage a piece of debris can cause is only partially dependent on speed. We all know F= m*a, mass is just as much a factor as speed/acceleration. A penny at terminal velocity might cause some skin damage but a bowling ball traveling a few m/s can kill.

For the kinetic energy carried by a moving body ½mv² is a more pertinent equation.

[Soda Popinski]

Interestingly, it's a real world solar powered ion drive. Here's the Wiki article on it.

It was orbiting fairly low (124 mile apoapsis / 121 mile periapsis), so it needed the continually active drive to counter-act solar decay. The 40kg of xenon fuel lasted 20 months.

[lajoswinkler]

I've heard of it, but I don't think it's a big deal. I'd be honored if pieces of it fall on my house.

[Seret]

Really? I'd be *&^% annoyed. Sod getting up on the roof to fix broken tiles in windy rainy autumn.

[Nibb31]

ESA would probably pay for the tiles, and you might be lucky to keep a piece of space memorabilia. Cool.

[rkman]

impact area is unknown.

Oh, it's not nearly that bad...the zone itself stretches to cover pretty much everywhere on Earth.

I find it interesting that even for NASA it is hard to predict where an uncontrolled atmospheric entry will end even if the orbit of the object is very well known.

I'm assuming that if the Earth would have no atmosphere it would be possible to predict precisely (let's say within a few tens of km, at most a few hundred) where it (pieces of it) would end up.

I think we all know from experience in KSP that atmospheric entry trajectory is kind of hard to predict, even Mechjeb can be iffy about it.

I think this thing coming down show just how hard of a problem it really it.

[K^2]

It's much, much harder with real atmosphere. If, like in KSP, atmosphere was absolutely static, then even with all of the other complexities, one could do much better than now. But we have weather and all sorts of associated movements in atmosphere. Down here, the pressure can vary by a few percent. Up here, fluctuations can be even higher, and that can throw off a shallow re-entry trajectory by a number of revolutions, making a crash location almost impossible to predict.

[kiwi1960]

I remember back in the 70's when the CIA was launching their spy satellite.... BIG BIRD... I knew it was big and weighed a lot, but had to search it on Google to remind myself just how big it was....

Launch vehicle: Titan IIID/34D

Total weight: 11,400 kg (25,100 lb), with mapping camera 13,300 kg (29,300 lb)

Reentry weight: 5,330 kg (11,750 lb)[67]

Max. diameter (main body): 3.05 m (120 in)[67]

Length (with mapping camera): 16.21 m (638 in)[67]

Orbit: elliptical, 100 miles by 150 miles

Scanners: television, radio, and high resolution camera

[Tommygun]

ESA would probably pay for the tiles, and you might be lucky to keep a piece of space memorabilia. Cool.

I think I'd be afraid to keep it with all the toxic materials they use in some of those satellites.

....and for the record, I just resealed my roof today.

There where several hole, but no signs of half melted alloys.

I remember back in the 70's when the CIA was launching their spy satellite.... BIG BIRD... I knew it was big and weighed a lot, but had to search it on Google to remind myself just how big it was....

Launch vehicle: Titan IIID/34D

Total weight: 11,400 kg (25,100 lb), with mapping camera 13,300 kg (29,300 lb)

Reentry weight: 5,330 kg (11,750 lb)[67]

Max. diameter (main body): 3.05 m (120 in)[67]

Length (with mapping camera): 16.21 m (638 in)[67]

Orbit: elliptical, 100 miles by 150 miles

Scanners: television, radio, and high resolution camera

Wow, that's like the world biggest disposable camera.

All that for four rolls of film.

Edited November 12, 2013 by Tommygun

[kiwi1960]

They said at the time that it could zoom in on a Russian outside the Kremlin and read the newspaper he was holding...

Whether true or not, I don't know...