Expert: Tom Whiting - 2/19/2009

Question
I'm a bit confused with the recent news item about our "crowded satellite space" (the news started coverage when 2 satellites had collided into each other).

If the geo-stationary orbit area is as "crowded" as the news imply, how in the world do we calculate trajectories for new satellites or even new NASA projects? I have visions of needle-in-a-haystack situations!

For that matter, wouldn't the "crowded skies" affect Earth-bound telescope activities? Or is this factor already filtered out by computers or something?

Thanks for your time on these queries. -- "I'm befuddled with the news"

Answer
Hi Dean,
First, the collision was not in the geostationary orbit at 22,800 miles high, it was in what is considered low or medium Earth orbit
at around 500 miles; one was polar (N-S)the Iridium satellite, while the Russian satellite was equatorial (W-E), so it was nearly a
90 degree collision, like two speeding trucks going through a
90 degree intersection and colliding.

That part of space, from say 150 miles to 22,000 miles is really
not that crowded....that's why this collision came as such a complete surprise.....even considering that there are over 17,000 orbiting bodies, considering the volume of space between those distances, there is an awful lot of empty space still available.

For instance, if you were "up" there just loitering and floating around, it would probably take several days to see, at your specific location, even one earth satellite whizzz by.  In fact, you may even have to go out of your way to even get to see one.  It's kind of like flying out over the Pacific Ocean in a commercial jetliner.  YOu know that at the same time there are literally thousands of other similar aircraft making the same trans-oceanic flights over the same ocean...but how many planes do you actually see on your trans-Pacific flight?  You're lucky if you even get to see one other aircraft because of the expanse of the Pacific Ocean.  AND, multiply that over 1000 times for the volume of space up there between 120 and 22,000 miles up.  {That's why the Iridium-Russian collision was such a complete surprise...I still can't hardly believe
it happened because the odds are so great against it...That was a one in a thousand odds event, or even higher}.

Now the geostationary equatorial orbit at exactly 22,800 miles, is a different (and special) story...there the satellite density is becoming a little crowded. Still, I've read where they try to maintain a 10-30 mile separation.
This area is easier to control because all satellites marking
geostation, are traveling at zero speed relative to each other and are all in the same orbit, AND some (if not all) are slightly maneuverable...relative to each other. So we humans can exercise some control on those geostationary satellites.
And the only reason it's getting a little crowded in the geostationary orbit is because there are 'preferred' positions
for communication....there are a lot of unused portions but everyone
wants to be out over the Eastern Pacific and over the Indian Ocean
and over the Alantic Ocean because for easier communications with
them.  It's those preferred hot spots in the geostationary orbits
that we have to exercise some caution.

So no, it has not become a needle-in-haystack situation as yet.
As far as telescopes, yes those that do astrophotography are hampered
occasionally by the reflected sunlight of a passing satellite.
But yes, today with Pro Photoshop computer programs (or whatever it's called), astrophotographers can eliminate the streak of light from a passing satellite in their astrophoto's if they want to.

You say you got your information from "the news"... that's not a
good idea for astronomy articles of any kind. News programs (along
with some "hot" magazines) tend to sensationalize the astronomy
subject.  Why? To sell magazines and sell the newscasts for ratings.  So best you do what us astronomers all do, stick with the
locations that do not sensationalize an event, at
www.skyandtelescope.com
www.spaceweather.com
www.spaceflightnow.com
Instead of relying on.....those other sources.
The above mentioned sources do NOT sensationalize the event.
As you found out, you were slightly "misled" by the so-called
"over-crowding" of space.  The liberals are currently doing the same
with their False global warming fears, when in actuality, we're cooling down.  But Global Warming makes for a "HOT" catastrophic...news story.  So ignore the facts, and just promote the ratings; and keep that free government money flowing toward our own...pet project for global warming.
Hope this Helps,
Clear Skies,
Tom Whiting
Erie, PA