Re: Globalstar flares

Ron Lee (ronlee@pcisys.net)
Mon, 16 Feb 1998 07:18:03 -0700

At 12:23 PM 2/16/98 +0100, you wrote:
>
>If I've understood the Globalstar satellites correctly, the satellites
>have two flat antenna arrays which both point at nadir, i.e. straight
>downwards.  If this is the case, any flares off the antennas will
>miss the earth.  A possibility exists if there are wide margins to the
>antenna pointing, say +- 5 degrees.  Then a reflected beam of light
>could strike the earth at a very low angle; thus, a flare could be seen
>when the satellite is low on the horizon in the direction of the sun.
>The satellite would of course also be very far away -- about 4500 km.
>
>(distance = cot(asin(ER / (ER + H))) * ER,
>            where ER = Earth's radius = 6378 km, and
>            H = satellite height above ground = 1414 km)

The picture on the globalstar web site shows them angled substantially
off the nadir point.  However. you may be referrring to the two octagonal
type structures I saw in several pictures. I had thought those were pointing
up, but that does not make sense.  If those are nadir pointing, then there
are two other sides (not counting the ends) that make up a triangular shape.

Those are the surfaces I assumed MIGHT produce flares.  Check out the 
"Photogallery" section of    http://www.globalstar.com/

Having checked out the picture again, I agree that the antennas pint down,
but the angled surfaces on either side still appear mirror-like.

Ron Lee