Iridium (satellite)

The Iridium satellite constellation is also a system of 66 active communication satellites and spares around the earth. Named for the element Iridium, it was originally to have 77 active satellites, but was later redesigned to have its current number, though the name was retained.

Iridium allowed worldwide voice and data communications using handheld devices. The Iridium service once failed financially and the earth stations were shut down. Its financial failure was largely due to insufficent demand for the service, the bulkiness and cost of the handheld devices compared to cellular mobile phones, and the rise of cellular GSM roaming during Iridium's decade-long construction period. The Iridium satellites were, however, retained in orbit, and their services have been re-established in 2001 by the newly founded Iridium Satellite LLC, partly owned by Boeing and other investors. The system is being mainly used by the US Department of Defense for its communication purposes, however, it is open for everyone with global communicaction needs like oil companies, scientists and globetrotters. Fixed contracts (about 25.- US$/month with 1.50 US$/min) are available as well as Pre-paid contracts with a certain time account.

The initial commercial failure of Iridium has had a dampening effect on other proposed commercial satellite constellation projects, including Teledesic. Other schemes (Orbcomm, ICO and Globalstar) followed Iridium into bankruptcy protection, while a number of proposed schemes were never constructed.

Phone rates from land lines to Iridium phones are $2 to $4 per minute. Iridium and other satellite phones may be identifiable to the listener because of the particular "clipping" effect of the data compression and the time lag due to the long travelling path of the signal.

However, Iridium-fun can be had for free:

Because of the satellites' peculiar shape with two polished door-sized antennas at 45 degree angles with the main bus, the Iridium satellites are responsible for the satellite flare phenomenon: On their orbits, the antennas directly reflect sunlight, creating a predictable and quickly moving illuminated spot of about 10km diameter when the reflected beam hits the earth. To a spectator this looks like an extremely bright flare in the sky with a duration of only a couple of seconds. Some of the flares are so bright (up to -8 magnitude) that they can be seen at daytime. Most impressive, however, they are during normal satellite viewing conditions, i.e. after dusk and before dawn.

External links

• http://www.heavens-above.com/ Iridium flare predictions based on geographic location.
• http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/iridium Iridium information from Lloyd's satellite constellations
• http://www.iridium.com/ official Iridium Satellite website