Satellite flare

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Satellite flare is the phenomenon caused by the reflective surfaces many satellites have today. In their orbits, the antennas or solar panels of satellites directly reflect sunlight.

In the case of the Iridium communication satellites, these flares are predictable and quickly moving illuminated spots of about 10 km diameter when the reflected beam hits the earth. To a spectator this looks like an extremely bright flare in the sky with a duration of only a few seconds (5-20 seconds). Some of the flares are so bright (up to -8 magnitude) that they can be seen at daytime, but they are most impressive after dusk and before dawn. In the case of Iridiums, the flares are caused by the antennas. Iridium satellites normally have a +6 magnitude (the boundary of visible objects in the night sky under the best of conditions).

The Iridium satellite constellation is composed of 66 satellites, some of which are currently inoperable and tumbling. The flares are caused by the MMAs, or main mission antennas. These are highly polished aluminum antennas that can act as a mirror to reflect light from below the horizon back to Earth.

This flashing has been of extreme annoyance to astronomers in that the brightness of the satellites disturbs observations and can damage sensitive equipment. Satellite flare can also be a problem for astrophotographers, as they can appear unwanted on shots of the night sky. Their high predictability, however, makes them an easy target for those who wish to photograph them.

External links

[Heavens Above] allows you to get predictions for when Iridium flares will be seen from your location
[Iridium flares widget for Mac OS X] Download free widget to get predictions based on heavens-above.com data
[Iridium flares wigdet for Opera] community widget for Opera Browser
[Images of Iridium flares]

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