Chris Johnson
05-30-2008, 04:14 PM
What is an 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 or longer.
Some of the flares are so bright (some get up to -8 magnitude, but rarely they can get to a brilliant -9.5) 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.
Heavens Above (http://www.heavens-above.com/) allows you to get predictions for when Iridium flares will be seen from your location
Iridium flares widget for Mac OS X (http://www.dashboardwidgets.com/showcase/details.php?wid=1411) Download free widget to get predictions based on heavens-above.com data
Iridium flares wigdet for Opera (http://my.opera.com/community/customize/widgets/info/?id=3847) community widget for Opera Browser
IridiumFlares prediction software (http://iridiumflares.sourceforge.net/) (Java application)
Iridium page at Visual Satellite Observer's Home Page (http://satobs.org/iridium.html) Images and further description of Iridium flares.
Bottom Earth-facing View: http://www.obsat.com/images/iridium/t_bottom.jpg Side View: http://www.obsat.com/images/iridium/t_body.jpg
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 or longer.
Some of the flares are so bright (some get up to -8 magnitude, but rarely they can get to a brilliant -9.5) 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.
Heavens Above (http://www.heavens-above.com/) allows you to get predictions for when Iridium flares will be seen from your location
Iridium flares widget for Mac OS X (http://www.dashboardwidgets.com/showcase/details.php?wid=1411) Download free widget to get predictions based on heavens-above.com data
Iridium flares wigdet for Opera (http://my.opera.com/community/customize/widgets/info/?id=3847) community widget for Opera Browser
IridiumFlares prediction software (http://iridiumflares.sourceforge.net/) (Java application)
Iridium page at Visual Satellite Observer's Home Page (http://satobs.org/iridium.html) Images and further description of Iridium flares.
Bottom Earth-facing View: http://www.obsat.com/images/iridium/t_bottom.jpg Side View: http://www.obsat.com/images/iridium/t_body.jpg