Iridium Flare Over Friends Creek, Illinois

June 05, 2010

20100605 – Saturday - Iridium Flare Over Friends Creek, Illinois
: Robert Arn
Summary Author: Robert Arn; Jim Foster

The photo above shows a dazzling iridium flare brightening a late summer sky. Iridium flares result from sunlight reflected off one of the many Iridium satellites still orbiting Earth. These satellites are equipped with solar panels designed to collect energy from the Sun. As they orbit the Earth, the angle they make to the Sun constantly changes. To correct for this, the satellite rotates in order to reposition the solar cells. During this rotation, there's a brief 10-30 second period when light from the Sun strikes the cells in such a way to reflect it toward the Earth's surface. This causes the characteristic flaring observed when the panels are still illuminated by the Sun; though from the viewer's perspective the Sun has already set. The reflection appears to gradually increase in brightness and then flares dramatically, on occasion reaching a magnitude -8, before fading from view. On clear evenings and or mornings, these flares can be spectacular. Photo taken on September 17, 2009 from Friend's Creek County Park, Illinois.

Photo details:
Camera Maker: Canon; Camera Model: Canon EOS DIGITAL REBEL XSi; Lens: 20mm; Image Date: 2009-09-17 19:49:37 -0500; Focal Length: 20.0mm; Aperture: f/3.2; Exposure Time: 100.000 s; ISO equiv: 800; Exposure Bias: none; Metering Mode: Matrix; Exposure: Manual; Exposure Mode: Manual; White Balance: Manual; Flash Fired: No (Manual); Color Space: Adobe RGB (1998)