Celebratory Gunfire Brings Down a Satellite

[ben m]

I wonder how soon they'll have the reentry area narrowed down? After all, I suspect that simply staying indoors will protect you from 99% of the risk. If you have 5 hours' warning, and you know the danger window to +/- 15 minutes, I bet you could get some blanket media coverage to tell everyone to stay indoors during the window.

But I bet it's not worth it. Since the 1/3200 number is an average over the whole Earth (population density 32/mi^2), if the debris track aims directly for a populated area (which is unlikely to begin with)---let's say Los Angeles county (2000/mi^2, or 60x the average Earth)---it's still only a 1-in-50 chance of one person getting hit. I'll bet that simply attempting to warn people (via reverse 911, saturation media coverage, etc.) would incur a much greater than 1-in-50 chance of killing someone due to misunderstandings, panic, etc. The only time you'd know enough to send out a mass warning would be if it was aiming for a very narrow target---if the thing was heading for *downtown* Los Angeles, or *central* Cairo, or whatever, maybe you'd want to hit the air raid sirens, but that's the level of detail you're never going to know until it's too late.

ETA: I see jadebox's last post answers my question.

TIP messages provide the best estimates of reentry time and location but
have large uncertainties. Even at T – 2 hours, the uncertainty of reentry
time is on average +/- 25 minutes for nearly circular orbits. This equates to
+/- 12,000 km on the Earth.

So, yeah, you're never going to even have a decision to make about air-raid-warnings, unless the decision is "warn everyone along a stripe from Wheeling to Edinburgh to Moscow".

 

[dogjones]

i don't think anyone said they are acceptable - not even nasa.

http://www.nasa.gov/pdf/585584main_uars_status.pdf

-- roger

zigactly!

 

[dogjones]

Assuming that pretty much every earth-to-orbit mission has a nonzero chance of smacking somebody upside the face with a chunk of launch vehicle or spacecraft, what would you say are the acceptable odds?

Sure, but I think these days the odds are considerably more, per the rest of this thread. Don't want to flog a dead Fred Smith. I was just sayin, really. If an asteroid was passing close enough to have a 1 in 3200 chance of hitting earth it would seem too close for comfort.

 

[dogjones]

I wonder how soon they'll have the reentry area narrowed down? After all, I suspect that simply staying indoors will protect you from 99% of the risk. If you have 5 hours' warning, and you know the danger window to +/- 15 minutes, I bet you could get some blanket media coverage to tell everyone to stay indoors during the window.

But I bet it's not worth it. Since the 1/3200 number is an average over the whole Earth (population density 32/mi^2), if the debris track aims directly for a populated area (which is unlikely to begin with)---let's say Los Angeles county (2000/mi^2, or 60x the average Earth)---it's still only a 1-in-50 chance of one person getting hit. I'll bet that simply attempting to warn people (via reverse 911, saturation media coverage, etc.) would incur a much greater than 1-in-50 chance of killing someone due to misunderstandings, panic, etc. The only time you'd know enough to send out a mass warning would be if it was aiming for a very narrow target---if the thing was heading for *downtown* Los Angeles, or *central* Cairo, or whatever, maybe you'd want to hit the air raid sirens, but that's the level of detail you're never going to know until it's too late.

ETA: I see jadebox's last post answers my question.



So, yeah, you're never going to even have a decision to make about air-raid-warnings, unless the decision is "warn everyone along a stripe from Wheeling to Edinburgh to Moscow".

Gotchya. Or just warn Fred. Not that he deserves it.

 

[spin0]

Amateur astronomer Thierry Legault recorded the tumbling UARS on video with his telescope. Looks great: http://legault.perso.sfr.fr/uars_110915.html

Little by little the satellites' orbit is getting lower, now 205 by 225 km.

As of Sept. 20, 2011, the orbit of UARS was 127 mi by 140 mi (205 km by 225 km). Re-entry is expected Sept. 23, plus or minus a day. It is still too early to predict the time and location of re-entry. Predictions will become more refined over the next two days.
http://www.nasa.gov/mission_pages/uars/index.html

Solar activity is a major factor here, it makes the satellite loose altitude faster and will advace its re-entry as already happened last week. And there's more to come. Yesterday there were six solar coronal mass ejections. One of them is directed to our way and is expected to make a glancing blow by Sept 22nd 23:00 UTC (+- 7 hrs).
See animation: http://iswa.gsfc.nasa.gov/downloads/20110919_093800_anim.tim-den.gif
Maybe we'll get both fireworks and auroras!

 

[rwguinn]

Amateur astronomer Thierry Legault recorded the tumbling UARS on video with his telescope. Looks great: http://legault.perso.sfr.fr/uars_110915.html

Little by little the satellites' orbit is getting lower, now 205 by 225 km.

As of Sept. 20, 2011, the orbit of UARS was 127 mi by 140 mi (205 km by 225 km). Re-entry is expected Sept. 23, plus or minus a day. It is still too early to predict the time and location of re-entry. Predictions will become more refined over the next two days.
http://www.nasa.gov/mission_pages/uars/index.html

Solar activity is a major factor here, it makes the satellite loose altitude faster and will advace its re-entry as already happened last week. And there's more to come. Yesterday there were six solar coronal mass ejections. One of them is directed to our way and is expected to make a glancing blow by Sept 22nd 23:00 UTC (+- 7 hrs).
See animation: http://iswa.gsfc.nasa.gov/downloads/20110919_093800_anim.tim-den.gif
Maybe we'll get both fireworks and auroras!

Yepper--atmosphere expanding. On a side note, idiots at National Geographic can't even get units right

But more than 1,100 tons (500 kilograms) of debris will probably survive the fiery plunge and slam down to Earth.

 

[excaza]

Yepper--atmosphere expanding. On a side note, idiots at National Geographic can't even get units right

Idiots? That's a bit rough for a minor error, don't you think?

 

[jadebox]

Sure, but I think these days the odds are considerably more, per the rest of this thread. Don't want to flog a dead Fred Smith. I was just sayin, really. If an asteroid was passing close enough to have a 1 in 3200 chance of hitting earth it would seem too close for comfort.

Start worrying:

http://neo.jpl.nasa.gov/risk/2011ag5.html



-- Roger

 

[dogjones]

Ooooohhh, shiii...

 

[rwguinn]

Idiots? That's a bit rough for a minor error, don't you think?

Yeah, what's an error of the magnitude 2x10³for a science publication...

 

[Agatha]

158kg of aluminium ought to be worth a bit at a scrapyard....

The Grauniad has a poll. Is it TEOTWAWKI or do you feel fine? http://www.guardian.co.uk/commentisfree/poll/2011/sep/22/falling-nasa-satellite?intcmp=239

 

[spin0]

The end is near.

Predicted Reentry Time: 23 SEP 2011 @ 22:07 UTC ± 9 hours


...and I feel fine.

 

[Verde]

Assuming that pretty much every earth-to-orbit mission has a nonzero chance of smacking somebody upside the face with a chunk of launch vehicle or spacecraft, what would you say are the acceptable odds?

The acceptable odds are zero. The actual odds are really close to that; in fact ZERO(+- a little bit). Unless you happen to be a dingo in Western Australia, or a dolphin in the South Pacific.

The largest piece of junk is going to be about the size of a fridge. The likely impact area is several hundreds of square miles, most of which are unpopulated.

I have no idea where they got the 1/3200 figure from, it makes no sense to me.

I will of course be erecting my anti-satellite shield over my house, just in case..

V.