Off Topic: see an I* satellite in the sky. . .
Low-Flying Satellites Staging a Global Show
By Mike Mills
Washington Post Staff Writer
Tuesday, April 28, 1998; Page C01
Stargazers have been seeing some strange lights flashing across the night sky.
But back off, Scully and Mulder, they're not some X-file government secret.
Instead, they're "Iridium flares," an astral phenomenon created by the world's newest satellite constellation. Since District-based Iridium began launching its 66 low-orbiting satellites early last year, people around the world have begun noticing brilliant flashes of light when they look toward the stars. No telescope is necessary.
"We watch them every night," said David Sands of the Austin Astronomical Society. "You'll be looking up in the sky, see a satellite moving, very faint, then it gets brighter than all get out," he said. Others say they resemble the beam of a car headlight.
The flares appear when rays from the sun are aligned to reflect off shiny aluminum surfaces on an Iridium satellite's antennas. Because the 66 satellites cross the sky at a low, 421-mile-high orbit, the reflections are brighter and more frequent than similar flashes created by higher, traditional geostationary satellites.
In September, Iridium plans to offer a new kind of mobile phone and paging service using the space-based network.
How do you know where, and when, to look for the flares? The German Space Operations Centre takes away much of the guesswork through its Web site (www.gsoc.dlr.de/satvis/). By entering the name of your town (or, better yet, your latitude and longitude coordinates), the Web site calculates the best time and sky position to see a flare from an Iridium satellite.
According to the German Space Operations Web site, tomorrow night will be a particularly good one for spotting an Iridium flare if you view it from the District or Alexandria. Look to the southeast at 74 degrees above the horizon at around 8 p.m. An object that looks like a slowly moving star will be Iridium satellite No. 29. Peak flare intensity will come at 10 seconds after 8:07 p.m. in the District, and 12 seconds past in Alexandria, according to the Web site's calculations.
The light intensity of the flare will be "-7," using a standard astronomical scale measuring the strength of light. A magnitude -7 event is 120 times brighter, for example, than the brightest star in the sky, Sirius, which has a magnitude of -1. Venus sometimes reaches -5 and the moon shines at -12.
"Anyone who has seen a magnitude -7 flare cannot fail to be impressed, and it would be easy to think you had seen something else, such as a UFO, if you didn't know what you were looking at," said Chris Peat, who developed and runs the German Space Operations Web site near Munich.
But location is everything in flare-spotting. Iridium 29's beam will hardly be visible to Maryland residents. At 10:57 p.m. and 34 seconds watchers in Gaithersburg can view Iridium 16 in the northeast at 10 degrees above the horizon, but it's only a -2 intensity. |
