Unidentified subject!

Jason Hatton (ROBERT.D.MATSON@cpmx.saic.com)
Tue, 10 Feb 1998 11:48:29 +0100

I've been following the recent discussion about the visibility of a bright
Iridium flare ellipse on the ground as seen from a plane or from space.
My intuition is that it would be visible from space (though not very
impressive), but probably not noticeable from an aircraft.  We've all
seen earthshine on a couple-day-old moon with no problem, and
though the moon is a much smaller source, I'm confident that moon-
shine on the earth would be easily visible from space.  (An astronaut
could answer that question definitively).

Now the radiance of an Iridium flare reflecting off the earth would be
40 times dimmer than earth-reflected moonshine at full moon.  Pretty
dim, but as long as the moon wasn't also illuminating that part of 
the earth, the contrast would probably be sufficient.  The odds
improve if the "ground" happens to be a cloud top.  And if the
spacecraft happened to be in the right geometry, a specular flare
reflection off the ocean could be even brighter.  (Quite a light path:
sun to satellite to ocean to second satellite!)  --Rob