The Iridium satellite constellation is a system of 66 active communication satellites with spares in orbit and on the ground. It allows worldwide voice and data communications using handheld satellite phones . The Iridium network is unique in that it covers the whole earth, including poles, oceans and airways. The service is interdicted by American embargoes in North Korea , Iran , Libya and Sudan ; if one tries to use the Iridium service in one of these countries it will not work.

The company derives its name from the chemical element known as Iridium ; the size of the satellite constellation projected in the early stages of planning was 77 – which is equivalent to the atomic number for Iridium.

The satellites are frequently visible in the night sky as satellite flares – a phenomenon typically observed as short-lived bright flashes of light.

History

Iridium communications service was launched on November 1 , 1998 and went into Chapter 11 bankruptcy on August 13 , 1999 . The first Iridium call was made by then- Vice President of the United States Al Gore . Motorola provided the technology and major financial backing.

Its financial failure was largely due to insufficient demand for the service, coupled with a massive initial capital cost running into the billions of dollars (the handsets could not operate until the entire constellation was in place). The increased coverage of terrestrial cellular networks (e.g. GSM ) and the rise of roaming agreements between cellular providers proved to be fierce competition. The cost of service was also prohibitive for many users, despite the continuous worldwide coverage of the Iridium service. In addition, the bulkiness and expense of the handheld devices when compared to terrestrial cellular mobile phones discouraged adoption among potential users.

Mismanagement has also been cited as a major factor in the original program's failure. In 1999, CNN writer David Rohde detailed how he applied for Iridium service and was sent information kits, but was never contacted by a sales representative. He encountered programming problems on Iridium's website and a "run-around" from the company's representatives. After Iridium filed bankruptcy it cited "difficulty gaining subscribers".

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

At one stage there was a threat that the Iridium satellites would have to be de-orbited; however they remained in situ and operational. Their service was restarted in 2001 by the newly founded Iridium Satellite LLC, which was owned by a group of private investors. Although the satellites and other assets and technology behind Iridium were estimated to have cost on the order of US$6 billion, the investors bought the firm for about US$25 million.

Present status

Iridium Satellite LLC claims to have 203,000 subscribers as of June 30, 2007, an 11% increase from the total by the end of the first quarter 2007. Revenue for the second quarter of 2007 was $66.7 million with EBITDA of $20.2 million. Revenue in 2006 was $212.4 million and EBITDA was $53.9 million.

The system is being used extensively by the U.S. Department of Defense for its communication purposes through the DoD Gateway in Hawaii . The commercial Gateway in Tempe, Arizona provides voice, data and paging services for commercial customers on a global basis. Typical customers include maritime, aviation, government, the petroleum industry, scientists, and frequent world travelers. Iridium satellites are now an essential component to communications with remote science camps, especially the Amundsen-Scott South Pole Station . As of December 2006, an array of 12 Iridium modems was put online providing 24/7 data services to the station for the first time. Total bandwidth is 28.8 kbit/s, making real time e-mail conversations finally possible.

Iridium and other satellite phones may be identifiable to the listener because of the particular "clipping" effect of the data compression and the latency (experienced as a noticeable lag or time delay) due to the electronic equipment used and the distances the signal must travel. Iridium operates at 2200 to 3800 baud , which requires very aggressive voice compression and decompression algorithms . The voice codec used is called Advanced Multi-Band Excitation . Iridium claims data rates up to 10 kilobits per seconds for their 'direct internet' service. Phones can be connected to computers using a RS-232 connection, as can the 9522A, which is just a tranceiver module. These can be used for data-logging applications in remote areas. This is a common practical use for Iridium's services, and the new Tsunami warning system uses Iridium satellites to communicate with their base. The remote device must be programmed to call the base at specified intervals, or it can be set to accept calls in order for it to offload its collected data. Despite the bandwidth limitations, transparent TCP/IP is supported. Latency is around 1500 milliseconds.

The former Iridium provided phones from two vendors, Kyocera and Motorola . Neither still manufacture these handsets. Kyocera phone models SS-66K and SD-66K are no longer in production but still available in the second-hand and surplus market. The Motorola phone 9500 is a design from the first commercial phase of Iridium, whereas the current 9505A model is the most current version of the handset and the 9522A is the most current version of the OEM L-Band Transceiver module designed for integration into specific applications. The 9505A phone is functionally identical to the 9505 but is no longer manufactured by Motorola and contains a slightly different set of components.