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Satellites: Ground
built 280 days ago
WorldSpace operates a pair of satellites: AfriStar (launched October 28, 1998) and AsiaStar (launched March 21, 2000). Each satellite has three beams transmitting in L-band between 1467 to 1492 MHz. Each beam transmits two TDM signals, where each TDM signal contains 96 Prime Rate channels. One of these signals is from the on-board processor, the other is a "transparent" channel transponded from the ground.
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GPS satellites continually broadcast their precise locations, and these can be read by small portable receivers, relatively inexpensive. Using a built-in computer, these receivers then derive their own precise position on the ground, within 10-50 meters. Russia operates its own system, GLONASS, and European countries are planning a third one.
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Navigational satellites are satellites which use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location. The relatively clear line of sight between the satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation systems to measure location to accuracies on the order of a few meters in real time.
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