Want to stay on top of all the space news? Follow @universetoday on TwitterAn Iridium satellite is one of 66 satellites that make up the Iridium satellite constellation. This particular group of satellites is basically used for communication, specifically for satellite phones, pagers and other integrated transceivers. The constellation got its name from the element iridium. In case you’re wondering where the resemblance lies, there’s none now. But during the planning stages, an assembly of 77 satellites (which is the atomic number of iridium) was envisioned, hence the name.
Through this assembly, calls can be made from one part of the world through a satellite phone which transmits the call to a satellite above it. That satellite then relays the information to another and so on until the data is received by one that is situated above a ground station near the desired recipient.
The data is beamed down to that ground station, which relays the information to either the public voice network or the Internet before reaching the recipient.
Since the constellation has access to the entire surface of the Earth, it is unparalleled in terms of coverage. This allows subscribers to enjoy very minimal interruption due to blind spots and other technical obstacles.
The Iridium satellite constellation is owned and operated by Iridium Satellite LLC, which is based in Bethasda, Maryland in the USA. The company reported about 320,000 subscribers by the of December 2008. One of its biggest users is the US Department of Defense, wherein the DoD pays $36 million per year for unlimited access.
Aside from the 66 that are required to be operational at the same time, the company also has backup satellites that are already in orbit, ready to substitute whenever a node fails. Each Iridium satellite operates at an altitude of about 780 km. They communicate with one another through Ka band (that’s 26.5-40Ghz) intersatellite links. This band can be found within the microwave range in the electromagnetic spectrum.
On February 10, 2009, an Iridium satellite collided with an obsolete Russian satellite. As promised, a backup satellite took the place of the ill-fated Iridium unit. The replacement procedure was completed 30 days after the accident.
Starting 2014, the first batch of next-generation Iridium satellites will be launched into orbit. On that same year, a good number of the existing ones will be decommissioned. Once complete, the new constellation will still be comprised of 66 simultaneously operating units. Four more will be added for backup.
Here in Universe Today, we’ve talked about the satellite collisions as well as how Iridium immediately replaced the destroyed satellite using an orbital spare.
NASA has some awesome pictures that you might want to see. One is of Iridium 52′s flare. Another was taken by Don Petit, from the ISS.