RE: Iridium Flares ground projection

Robert G Fenske Jr (
Tue, 3 Feb 1998 13:44:39 -0600 (CST)

On Tue, 3 Feb 1998, Tyler MacKenzie wrote:

> I've wondered about the spotlight projection myself, and don't think it
> would be anything spectacular.  For Randy's 1200km distant Iridium,
> assuming all the light falls in the 10x20km rectangle and the albedo of
> the antenna is 100% (at 188x86cm) the light would be "diluted" (dimmed) by
> about a factor of 8 BILLION! (or about 20 magnitudes from the sun itself).
> I have a feeling this would be somewhere on the order of 100,000 times
> dimmer insolation to the Earth as that from the moon (invisible to all
> but superman).

	Can't see how you can write that.  Moonlight is fairly bright and
easily casts shadows so I would suppose that if moonlight swept by in a
quick fashion one would notice it.  Venus (max -4.7 mag) has been reported
to cast shadows.  I think it would be easier (but not necessarily easy) to
watch for shadows cast by an Iridium than to watch for Iridium light
sweeping by.  It is also possible that high altitude aircraft or an
imaging satellite could see the light cone reflecting off cloud tops or
open ocean.

Robert Fenske, Jr.    Sw     |The Taming the C*sm*s series:
Southwest Research Institute            /R---\  |
Signal Exploitation & Geolocation Div  | I    | |"The Martian canals were the
San Antonio,Texas USA  ph:210-522-3931  \----/  | Martians' last ditch effort."