Satellite flare

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Image:Iridium 84 flare 20061120.png

Satellite flare is the phenomenon caused by the reflective surfaces on satellites (such as antennas or solar panels) reflecting sunlight directly on to the Earth below and appearing as a brief, bright "flare".

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[edit] Iridium satellite flare

The Iridium communication satellites have a peculiar shape with three polished door-sized antennas, 120 degrees apart and at 40 degree angles with the main bus. The forward mirror faces the direction in which the satellite is travelling. Occasionally an antenna will directly reflect sunlight down to the Earth, creating a predictable and quickly moving illuminated spot of about 10 km diameter. To an observer this looks like an extremely bright flare in the sky with a duration of a couple of seconds.

Some of the flares are so bright (up to -8 magnitude) that they can be seen at daytime, but they are most impressive at night. This flashing has been of extreme annoyance to astronomers as the flares occasionally disturb observations and can damage sensitive equipment.

When not "flaring" the satellites are often still just visible to the naked eye - a typical magnitude is 6, similar to a dim star.