Iridium 75 was part of a planned commercial communications network comprised of a constellation of 66 LEO spacecraft. The system will use L-Band to provide global communications services through portable handsets. A total of 125 spacecraft will be built by Lockheed for more than $700M. Commercial service is planned to begin in 1998. The system will employ 15-20 ground stations with a master control complex in Landsdowne, VA, a backup in Italy, and a third engineering center in Chandler, AZ. The spacecraft was 3-axis stabilized, with a hydrazine propulsion system. It had 2 solar panels with 1-axis articulation. The system employed L-Band using FDMA/TDMA to provide voice at 4.8 kbps and data at 2400 bps with 16 dB margin. Each satellite had 48 spot beams for Earth coverage and used Ka-Band for crosslinks and ground commanding.
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