From Robert Sheaffer's "Psychic Vibrations" column in the
January/February 1998 _Skeptical Inquirer_:
"During the first fifty years of Saucerdom we had no
shortage of objects in the sky to cause UFO sightings. Now,
in the fifty-first year of that era, we suddenly must
contend with an entirely new phenomenon guaranteed to
bamboozle the casual skywatcher. A new generation of global
communications technology is now being developed and
deployed, under the name `Iridium.' This is a series of
communications satellites developed by Motorola's Satellite
Communications Division to provide direct satellite-to-
telephone communications, virtually anywhere on the globe.
While the system is not yet operational, the first Iridiums
were launched May 5, 1997 (for more information, see
http://www.iridium.com:80).
     Almost immediately, amateur satellite watchers began
reporting remarkable things. While the Iridium satellites
are not particularly large and are normally visible only
with the aid of binoculars, satellite watchers were
astonished to see one or more of the Iridiums suddenly flare
up to be as bright as the brightest stars, then fade back to
invisibility. Additional skywatching revealed that the
Iridium satellites would often flare so brightly as to
actually outshine Jupiter, or even Venus.  Indeed,
experienced satellite watchers have occasionally reported
flares from the Iridium satellites so bright as to rival the
first-quarter moon, and some have even been observed during
daylight.
     Mathematical analysis by Rob Matson and Randy John,
both authors of satellite-tracking software, quickly yielded
an answer to the mystery. The four Main Mission Antennas of
an Iridium satellite, developed by Raytheon, are oriented at
90 degrees to each other. While they are not especially
large (188 by 86 cm), they consist of highly reflective
aluminum flat plates, treated with silver-coated Teflon for
thermal control. Each being maintained at an angle of 50
degrees from Earth toward the satellite's zenith, one always
facing in the direction of the satellite's travel, they
probably represent the best flat reflecting surfaces ever to
orbit Earth. When the angle is just right between the
satellite, the observer, and the sun, sunlight reflecting
off the silvered panels results in the sudden appearance of
a dazzingly bright, slow-moving, unexpected object that
disappears in about twenty seconds or less--the perfect
culprit to cause UFO sightings. The flare-up lasts just long
enough for someone to shout "Look! Up there!", giving the
crowd a few seconds of dazzling brilliance, then fading
completely from view. (For more information on the Iridium
flares and to download software to predict them, see
http://www2.plasma.mpe-garching.mpg.de/sat/vsohp/
iridium.html.)
     Flares from the thirty-four Iridium satellites now in
orbit are visible sporadically in most locations around the
globe, typically occurring during the time of evening or
morning twilight. When the Iridium program is fully
deployed, it will consist of sixty-six satellites. Hence,
the flares can be expected to increase in frequency and
continue indefinitely.
     While we are on the subject of satellites that mimic
UFOs, we should mention Superbird A, a dead Japanese
communications satellite now adrift in the satellite
graveyard just outside the Clarke belt of geosynchronous
orbit, many times more distant than the Iridium satellites.
It, too, sometimes reflects the sun from both the front and
back side of its huge solar panels as it tumbles
approximately once every twenty-three seconds. When the
satellite is favorably placed in the sky, for a period of
about six minutes per evening observers can see millisecond-
duration pulses of light every 11.6 seconds, looking for all
the world like a strobe flash hanging in the heavens.
     While not nearly as bright as the Iridium reflections
because of its great distance, Superbird A is the only
object in or near geosynchronous orbit regularly visible to
the naked eye. Because of its distance from Earth, Superbird
A can be expected to remain in orbit for intervals measured
in `eras,' not `millenia.' The night sky will continue to
glitter with space junk long after we're all dead."
--- msgedsq 2.0.5
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