Bus sized UARS satellite crashing back to Earth Friday

[TedTheLed]

this is for my area , 90265 , so. calfornia, you can look up yours at

http://spaceweather.com/flybys/


* September 23 * * * * *

* Satellite Rise time Direction to look Transit time Max elevation Magnitude

* UARS 07:53:36 pm SSW 07:54:44pm 26° 2.0 (visible)

 

[Steve K]

'Nuclear powered satellites' google search yields 320,000 hits
Here is just a few:

http://www.spacedaily.com/reports/Nuclear_Power_In_Space_999.html

this article speculates that nuclear power would be needed for exploration of the moon or a long term mission on Mars. Not particularly relevant to low earth orbit satellites.

Nuke powered satellite expected to hit Earth (old news - this already happened)
http://www.nytimes.com/1988/05/14/w...atellite-expected-to-hit-earth-in-summer.html

that's much more relevant. Probably a RTG system?
As was mentioned, these are made with low density radioactive masses that just get warm. Thermocouples or thermo-electric devices then use the temperature difference between the mass and the rest of the spacecraft to generate electricity. A very nice, simple system with no moving parts. Usually reserved just for deep space probes where solar radiation is very weak, but could be used for LEO (low earth orbit) too, I guess. The downside is that they were heavy and more expensive to launch. In the early days, photo-voltaics were built with rigid substrates instead of the spiffy modern PV's that are flexible enough to roll up for launch and unfurl like a flag later. The early PV's might have been too complicated or unreliable, perhaps?? (just a guess)

But if you are saying you know the UARS has no nuclear power than that's good news.

I know that the satellite depended on the MPS module to convert power from the PV panels and provide battery bus power to the satellite, so there was no reason for any nuclear power source. Not to say that there couldn't have been some small bit of radioactive material as part of the instruments on board (similar to the radioactive bits in some smoke detectors).

Steve K.

 

[LEDAdd1ct]

When I visit the spaceweather site and punch in the nearest zip code to me, it offers a time to see UARS on the 26th. Is it extrapolating future orbits? I thought it was coming down tomorrow...?

EDIT: North America is out!

 

[Steve K]

i...
a couple of big chunks expected . is there an expected impact velocity for these chunks ?

the NASA analysis does list impact velocities on page 8. The reaction wheels are expected to be the fastest bits, with a velocity of 107m/s. The largest impact energy, though, is the "SSPP structure", with an impact energy of 153kJ. I'm still trying to figure out what "impacting ballistic coefficient" really means. It's in units of kg per cubic meter, so is it just density??

interesting stuff!

Steve K.

 

[DM51]

If I did math right, it's one in 187,500 chance world wide.
Or one in 90,625 chance of hitting one person in the USA

Could you explain how you calculated this? :thinking:

 

[LEDninja]

Late Show with David Letterman:
"A satellite is headed toward earth and the people at NASA have no idea where it will land. How would they know? It's not like they're rocket scientists."

:shakehead :shakehead :shakehead

 

[cdrake261]

Could you explain how you calculated this? :thinking:

The proability of an object hitting just one person out of 3200, right? Divide 1 by 3200 and you get 0.0003125 then you multiply that by whatever population(earth = 6 billion, America = 290 million).

0.0003125 * 290,000,000 = 90,625

So my math is off... It's 90,625 out of 290,000,000 probability... Just reduce that to simple fractions

29 out of 92,800....which still comes out to one person out of 3200 would still be hit by something.

Ask me, that's a damn good probability.

 

[DM51]

I'm afraid that's the wrong way to calculate it. You multiply the population that could be affected by 3200. The probability that someone on earth could be hit by it is 1 in 3200. If you single out one individual in the entire world's population and ask what the chances are of him personally being hit, you multiply the 3200 by 6,000,000,000 and that gives you the 1 in 20,000,000,000 figure.

However, beerwax may be right (post #36) and they may be able to steer the satellite into an orbit that avoids most of the world's population. That would affect the odds. It would reduce the chances further if you happen to live in a "safe" zone, and increase them if you are in the possible impact area. It's a big "if" though, and I rather doubt they have any real control remaining over where it is going to come down.

 

[Steve K]

However, beerwax may be right (post #36) and they may be able to steer the satellite into an orbit that avoids most of the world's population. That would affect the odds. It would reduce the chances further if you happen to live in a "safe" zone, and increase them if you are in the possible impact area. It's a big "if" though, and I rather doubt they have any real control remaining over where it is going to come down.

Yeah, the only control exercised over the satellite was back in 2005, if I understand things correctly. That was when they applied as much reverse thrust as they could and only managed to slow it enough to drop it a bit lower in altitude. Any remaining control is somewhere in the range of slim to none (and I'm betting on "none").

I heard someone on the radio compare it to dropping a coin into an aquarium and trying to predict where it will land. The only difference is that it doesn't take the coin 6 years to get to the bottom... well, there's also the assurance that the coin will land in water and not hit anybody.

Steve K.

 

[EZO]

Sorry, I had to remove this image because too many people were hotlinking to it on my server from other web sites.

 

[fyrstormer]

The Earth gains 40 tons of mass every single day, from falling space dust and rocks. 40 tons of space rocks, falling out of the sky every day. This satellite is totally insignificant in the big scheme of things.

 

[Steve K]

The Earth gains 40 tons of mass every single day, from falling space dust and rocks. 40 tons of space rocks, falling out of the sky every day. This satellite is totally insignificant in the big scheme of things.

Is there any data on the size of the chunks striking the earth daily? i.e. how often does a 100 pound chunk strike?

hmmm... just another day until we get close to the re-entry time!! Has anyone started a pool for the re-entry time? Put me down for 4:30pm, central time (GMT + 5, I think). My theory is that one of my old batteries will hit me just as I step out of work.

regards,
Steve K.

 

[beerwax]

Is there any data on the size of the chunks striking the earth daily? i.e. how often does a 100 pound chunk strike?

regards,
Steve K.

might be 99.9 % 'quite tiny' . anything 100lb would make the news ? wouldnt you get a crater and some neat metorite fragments. and there might be a higher average velocity for natural space junk as compared to manmade space junk ?

when the little green men from the next galaxy come to visit they are going to take one look at all our space junk and think ' gee these guys are messy ' .

anyway cool science question how do they measure the change in the mass of the earth over time?

cheers

 

[blasterman]

In fact, I believe one of the Voyager probes are still working, although some of the instruments have been shut down

Last I checked both probes were functional, receiving and transmitting data, and cruising through the heliopause on their Interstellar Mission.

Not bad for 70's technology.

 

[Meganoggin]

Has UARS hit yet? Nothing on the BBC. Can I take my helmet off?

 

[TedTheLed]

here's the latest news I could find at the moment, off the coast of California, trajectory Seattle-ish

http://reentrynews.aero.org/1991063b.html

 

[PhotonWrangler]

OK, so the satellite that was originally possibly going to hit the US, then definitely not going hit the US, then will hit the US, was originally falling faster than expected, then slower then expected, and now falling faster again. Got that?

Screw it. I'm wearing my helmet tomorrow.

 

[Flying Turtle]

I'm heading outside right now. My yard needs a nice crater.

Geoff

 

[JacobJones]

No free goodies from NASA in my garden. Apparently bits of it have been found in Alberta

 

[PapaLumen]

UPDATE #15 - NASA's decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty.

UPDATE #14 - NASA's decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The satellite was passing eastward over Canada and Africa as well as vast portions of the Pacific, Atlantic and Indian oceans during that period. The precise re-entry time and location are not yet known with certainty.