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Technical details Air interfaceCommunication between satellites and handsets is done using a TDMA and FDMA based system using L-band spectrum between 1616 and 1626.5 MHz. Iridium exclusively controls 7.775 MHz of this and shares a further 0.95 MHz. In 1999 Iridium agreed to timeshare a portion of spectrum, allowing radio astronomers to observe hydroxyl emissions; the amount of shared spectrum was recently reduced from 2.625 MHz.
In addition to the Air Force’s 24 NAVSTAR global positioning system (GPS) satellites, OS/COMET is used by the entire constellation of more than 70 satellites owned by Iridium LLC
In 1967 Dr. Coffman joined Lockheed's Space Systems Division as a guidance and control systems analyst. After leading the development of several major space programs and large ground data processing systems ... and the Corporation's work on Iridium.