May 25, 2009
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An independent government report suggests that the accuracy of GPS signals could deteriorate in the next
few years because of some delays in new satellite launches.
However, the Air Force says it has plenty of methods of keeping up the navigation system increasingly
relied on by drivers and cell phone users.
In April, the GAO (Government Accountability Office) reported that there is a risk that launches of
new satellites will not keep pace with the wear and tear on the Global Positioning System.
Called IIF, the next generation of GPS satellites has been affected by launch delays and cost overruns.
Boeing said the delays were due to design changes necessary to ensure that the satellites would last longer.
The work is now done, and the first IIF is slated to launch in November, nearly three years behind schedule.
This could mean that the accuracy and reliability of hundreds of millions of civilian and military GPS
devices including everything from "buddy finder" cell phone applications to guided bombs could degrade until
new satellites are in orbit.
Though it's now in widespread civilian use, GPS was originally developed for the military, and it's still
mostly managed by the Air Force.
The investigative arm of Congress, GAO said the chief risk is that the following generation of satellites,
IIIA, will be delayed in a similar fashion. Lockheed Martin is now building that series, and the first are
scheduled to launch in about five years from now.
The Air Force's mission is to maintain a group of 24 working satellites, virtually ensuring that at any time
there are at least four in the sky above any point on the Earth. That's the minimum number needed for a GPS
device to compute its location by measuring the slightly different amounts of time it takes for radio signals
to reach it from each satellite.
However, the satellites don't work forever... A few launched in the early ’90s are still in operation, but
most have shut down. The delayed launch of the IIF series means that for a few years, satellites could be
failing faster than they're being replaced.
Lieutenant Colonel Tim Lewallen, deputy director of GPS at Air Force Space Command at Peterson Air Force Base
in Colorado agreed with the GAO's conclusion that there is a risk that service could degrade. But he was also
quick to point out that the risk is very small.
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Source: eWeek.
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