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ESA: Small meteorite will safely impact atmosphere tonight over northern France

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Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#11

Post by cshimmin »

version_five wrote: post #8
dredmorbius wrote: post #4

Impactor is ~1m in size, and projected impact time is 04:00 +/- 10 minutes CET (03:00 UCT). That's about three hours from now as I write this. My very off-the-cuff estimate is that a 1m impactor might mass anything from a few hundred kilos to a few tonnes, depending on composition (less for ice / chondrites, more for a heavy nickel-iron meteorite). Looking forward to the skycam views.

Stupid question: if the impact time is +/- 10 minutes, doesn't that translate into a lot of uncertainty for where it will hit? How do they know it's going to be Rouen?

Yes that's exactly right. You can see this information in the plot attached to the linked Twitter post. There is a range of times (indicated by color) and the corresponding projections for impact location. But note that meteors can be seen from quite far away. Large fireballs can be heard for dozens of miles around! Also, they posted a more recent update that the estimate is zeroing in on Rouen.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#14

Post by cshimmin »

dredmorbius wrote: post #9
version_five wrote: post #8

Earlier quoted context omitted.

Stupid question: if the impact time is +/- 10 minutes, doesn't that translate into a lot of uncertainty for where it will hit? How do they know it's going to be Rouen?

My (lay, nonexpert) understanding is: - The centroid of probability is near Rouen. - Earlier/later impact probability would be along a path along the movement/orbit of the impactor. I'm going to guess that that's largely east-west track, though with a possible orbital inclination. - The probability distribution across that range is likely far higher near the centre than at the extremes. - Relative motion of Earth's r…

Hmmm, interesting analysis, but 12,000km is 3x wider than continental US. Based on the plot from ESA's projection, the track over the +-10m period is much smaller than France.

I think the issue with your reasoning is that when you are dealing with orbits, you cannot really talk separately about position and (relative) velocity. Instead, for a given orbital trajectory, the position completely defines the speed. Moreover, your estimate might tell us how far _in space_ the impact would be given +/- 10min, but since both earth and asteroid are moving though space that doesn't really tell us much about how far apart it would be in an earthbound reference frame.

In practice, I don't think they can accurately measure the position OR speed of an object like this... Instead, they make multiple observations over time and can fit the "shape" of the orbit, which can be done even with a fair amount of noise since we know all orbits are elliptical. If the object's orbit doesn't intersect Earth's, there's no impact. If the orbits do interest, there _may or may not_ be an impact event. To determine this, you have to figure out if both the object and the earth will be at that intersection point, _at the same time_.

I'm guessing this is why the quoted uncertainty is given in minutes.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#15

Post by technothrasher »

jacknobody wrote: post #6

That's a meteor. Meteorites are different - they're the ones that hit the dirt.

If we're going to be pedantic, it's actually a meteoroid. Meteoroid is the object, meteor is what happens when it hits the atmosphere, and meteorite is when it has hit the ground.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#16

Post by version_five »

rvba wrote: post #13
GalenErso wrote: post #12

Could a F-22 shoot it down? /s

Ignoring the sarcasm marker. F15s could fire anti satelite missiles in early 1980s. Who knows what "toys" are available 40 years later. https://en.m.wikipedia.org/wiki/ASM-135_ASAT

But this isnt an orbiting satellite, it's an object moving at 20 km/s (quoting another post, I dont really know in what direction or relative to what) which is ~Mach 60. I don't know how that compares to satellites - is it close enough we'd expect an anti-satellite missile to work?

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#18

Post by h2odragon »

version_five wrote: post #16
rvba wrote: post #13

Earlier quoted context omitted.

Ignoring the sarcasm marker. F15s could fire anti satelite missiles in early 1980s. Who knows what "toys" are available 40 years later. https://en.m.wikipedia.org/wiki/ASM-135_ASAT

But this isnt an orbiting satellite, it's an object moving at 20 km/s (quoting another post, I dont really know in what direction or relative to what) which is ~Mach 60. I don't know how that compares to satellites - is it close enough we'd expect an anti-satellite missile to work?

I think we might be able to put something in front of it; but at that speed I dont think anything we loft does not do more than begin the party early. All the energy it's going to release pretty much happens in the same path, we might just begin the breakup and distribution a second or two before the air otherwise would have.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#19

Post by margalabargala »

version_five wrote: post #16
rvba wrote: post #13

Earlier quoted context omitted.

Ignoring the sarcasm marker. F15s could fire anti satelite missiles in early 1980s. Who knows what "toys" are available 40 years later. https://en.m.wikipedia.org/wiki/ASM-135_ASAT

But this isnt an orbiting satellite, it's an object moving at 20 km/s (quoting another post, I dont really know in what direction or relative to what) which is ~Mach 60. I don't know how that compares to satellites - is it close enough we'd expect an anti-satellite missile to work?

Can't speak to the missiles, but objects in low earth orbit travel at around 7km/s relative to the earth.

The benefit of this sort of task is in both cases the target object doesn't move of its own accord, so presumably if you can predict the path of the object with enough precision then it would work. Clearly we can pinpoint a 1m satellite, but no idea on the error bars for a 1m meteoroid.

Re: ESA: Small meteorite will safely impact atmosphere tonight over northern France

#20

Post by throwanem »

GalenErso wrote: post #12

Could a F-22 shoot it down? /s

The continuous-rod warhead in a Sidewinder will rip the hell out of an aircraft, which is made of tinfoil wrapped around complications. A rock from space, by contrast, is made out of rock wrapped around rock.

Assuming charitably that the missile could generate an intercept, you would probably get some sparks, maybe more or less depending on how much of the rock is actually nickel and iron. But basically, the rock is a rock. An AIR-2 Genie likely wouldn't bother it all that much beyond maybe a surface glazing and some neutron activation. The most a Sidewinder will do is expensively nothing.

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