Re: Question on iridium sats colors

Tony Beresford (
Sun, 27 Jun 1999 12:12:24 +0930

At 05:08 27/06/99 , Michael Boschat wrote:
> I've noticed that some Iridium satellites as they begin to diminish
>in brighteness flash a tint of red color. I was wondering if this was
>just do to the solar panel composition and the angle the sunlight hits
>it or more of an atmospheric effect?
Mike, the flash is due to reflection of the phased array antennae not
the solar panels. These are mostly tracking the Sun , so cant reflect
solar light onto the Earth's surface. They also of much lower reflectivity
(say 4%),than the silver coated teflon panels that cause the effect. 
The naked eye ( mag 2,2.5) flashes from abandoned comsats at geostationary,
and near geostationary satellites are from solar panels, very large
ones( often 30 square meters). If one translated Max brightness
Iridium reflections to 40,000Km ranges they would be about mag 0.
Tony Beresford