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Subject: DoD halts orders for 'selective availability' GPS
Softwar    9/19/2007 10:59:44 AM
http://www.eetimes.com/rss/showArticle.jhtml?articleID=201807477&cid=RSSfeed_eetimes_newsRSS DoD halts orders for 'selective availability' GPS The Defense Department has ended procurement of Global Positioning System satellites with hardware for a "selective availability" feature. The move implements in architecture what former President Bill Clinton ordered in May 2000: The end of the GPS "off" feature. While the order apparently does not apply to GPS Block IIF satellites which Boeing Co. has in the production pipeline, it will apply to future GPS III satellites. Two trends were at work warranting the end of the availability hardware. First, the European Space Agency is moving forward with the rival Galileo navigational network, though the system has been plagued with delays. In addition, the new GPS III will feature new military-only frequencies which alleviates the need to turn off signals in order to protect national security. A Pentagon statement said the decision "reflects the United States' strong commitment to users by reinforcing that this global utility can be counted on to support peaceful civil applications around the globe." When President Clinton ordered selective availability values set at zero in existing GPS satellites in May 2000, he cited the need to reassure civilian and commercial users that the network would not be shut down or degraded. Clinton also cited the wide use of land-based commercial "workarounds" for military dithering of signals, such as Differential GPS, that made selective availability features obsolete. GPS is a 24-satellite network of Navstar navigational satellites that transmit signals to users, giving them an accurate position in three dimensions along with a time stamp. While it was originally developed in the 1970s as a navigational aid for submarine-based Trident nuclear missiles, its commercial use has expanded well beyond vehicle and hiker navigation to include network timing control for accurate delivery of packet communications. Boeing announced production of the first GPS IIF satellite on Sept. 12, a generation that features a new civil code, a new encrypted military code and satellite crosslinks. GPS III, slated for initial launch in 2012, will carry a range of new features dubbed "Navwar," including significant upgrades in transmitter power that provide resistance to jamming and an integrated nuclear detonation detection system.
 
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ArtyEngineer       9/19/2007 8:51:25 PM
I neer understood why this feature was termed "Selective availability"  It wasnt as if the system was turned of or made unavailable, but rather that a bias error could be put into the system so that anyone not using a "Military" GPS reciever would not have and accurate location.
 
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