What are the odds of a satellite re-entering over water?

[I'm approaching the Desktop Project endgame here; I'm almost out of
pictures to post. I've done this every day for weeks, and my computer
desktop is almost clean! Of course, more stuff keeps coming in, so I
could do this forever. But that would be cheating. Sweet, sweet
cheating.]

I’ve got something different for you today. Over the past few weeks
I’ve posted an illustration, and a couple of dozen pictures, but no
graphs! That’ll change now, and I think this particular set of plots
is nifty.

Whenever a big satellite is about to re-enter Earth’s atmosphere —
like UARS, or ROSAT, or Phobos-Grunt — the media freak out. You start
seeing numbers being thrown about of the odds of getting hit by a
chunk of flaming debris, and I get lots of panicked email and tweets.
Then I have to point out to people that the Earth has a lot of real
estate for a satellite to come down on, and of that, 3/4 is water. And
most of that is Pacific Ocean. So really, the most likely scenario is
a re-entry into the Pacific, or some other ocean, and that’s that.

But is that really true? After all, satellites can have different
orbits, inclined with respect to the Earth’s equator. So the odds of
getting dumped in the ocean might be different for a satellite that’s
over the equator versus one in a polar orbit (that is, orbits almost
completely in a north/south direction).

Happily, orbital debris specialist Mark Matney did the math! In a
paper published in the Orbital Debris Quarterly Newsletter (bet you
didn’t know that existed!) he calculated those odds. He created two
graphs for the paper, and both are really cool if you’re a graph nerd
like I am.
Here’s the first one:

http://blogs.discovermagazine.com/ba...=Google+Reader

On Tue, 17 Apr 2012 17:25:05 -0400, Metspitzer
wrote:

[I'm approaching the Desktop Project endgame here; I'm almost out of
pictures to post. I've done this every day for weeks, and my computer
desktop is almost clean! Of course, more stuff keeps coming in, so I
could do this forever. But that would be cheating. Sweet, sweet
cheating.]

I’ve got something different for you today. Over the past few weeks
I’ve posted an illustration, and a couple of dozen pictures, but no
graphs! That’ll change now, and I think this particular set of plots
is nifty.

Whenever a big satellite is about to re-enter Earth’s atmosphere —
like UARS, or ROSAT, or Phobos-Grunt — the media freak out. You start
seeing numbers being thrown about of the odds of getting hit by a
chunk of flaming debris, and I get lots of panicked email and tweets.
Then I have to point out to people that the Earth has a lot of real
estate for a satellite to come down on, and of that, 3/4 is water. And
most of that is Pacific Ocean. So really, the most likely scenario is
a re-entry into the Pacific, or some other ocean, and that’s that.

But is that really true? After all, satellites can have different
orbits, inclined with respect to the Earth’s equator. So the odds of
getting dumped in the ocean might be different for a satellite that’s
over the equator versus one in a polar orbit (that is, orbits almost
completely in a north/south direction).

Happily, orbital debris specialist Mark Matney did the math! In a
paper published in the Orbital Debris Quarterly Newsletter (bet you
didn’t know that existed!) he calculated those odds. He created two
graphs for the paper, and both are really cool if you’re a graph nerd
like I am.
Here’s the first one:

http://blogs.discovermagazine.com/ba...=Google+Reader

As good as this all is, it won't stop some people from doing their
Chicken Little routine everytime there's a sat dunk. All they have to
do is move a decimal point here or screw up a metric conversion there.
and all you hear is...

THE S K Y IS F A L L I N G - THE S K Y IS F A L L I N G

Maybe somebody should write a nursery story about that? You'd think
there'd be something in human lore about this by now...

http://en.wikipedia.org/wiki/Chicken_Little

Happy days *and*...
Starry starry nights !

--
Indelibly yours,
Paine @ http://astronomy.painellsworth.net/
Only you can make the most of yourself.