Satellite flareThe forward antenna faces the direction in which the satellite is travelling. To an observer this looks like an extremely bright flare in the sky with a duration of a few seconds. Ranging up to -8 magnitude (rarely to a brilliant -9.5), some of the flares are so bright that they can be seen at daytime; but they are most impressive at night.
Satellite flare (also known as satellite glint) is the phenomenon caused by the reflective surfaces on satellites (such as antennas or solar panels) reflecting sunlight directly onto the Earth below and appearing as a brief, bright 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. Occasionally an antenna will reflect sunlight directly down to the Earth, creating a predictable and quickly moving illuminated spot of about 10 km diameter.
This flashing has been some annoyance to astronomers, as the flares occasionally disturb observations and can damage sensitive equipment. When not flaring, the satellites are often visible crossing the night sky at a typical magnitude of 6, similar to a dim star. .