advax at triumf
May 21, 2009, 6:48 PM
Post #1 of 2
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FYI - possible GPS degradation in next few years
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"It is uncertain whether the Air Force will be able to acquire new
satellites in time to maintain current GPS service without interruption."
http://www.gao.gov/products/GAO-09-670T
Where does this leave the wide span of military, civil, and other user of
GPS? If the Air Force does not meet its schedule goals for development of
GPS IIIA satellites, there will be an increased likelihood that in 2010,
as old satellites begin to fail, the overall GPS constellation will fall
below the number of satellites required to provide the level of GPS
service that the U.S. government is committing to providing. The
performance standards for both (1) the standard positioning service
provided to civil and commercial GPS users and (2) the precise
positioning service provided to military GPS users commit the U.S.
government to at least a 95 percent probability of maintaining a
constellation of 24 operational GPS satellites. Because there are
currently 31 operational GPS satellites of various blocks, the near-term
probability of maintaining a constellation of at least 24 operational
satellites remains well above 95 percent. However, DOD predicts that over
the next several years many of the older satellites in the constellation
will reach the end of their operational life faster than they will be
replenished, and that the constellation will, in all likelihood, decrease
in size. Based on the most recent satellite reliability and launch
schedule data approved in March 2009, the estimated long-term probability
of maintaining a constellation of at least 24 operational satellites
falls below 95 percent during fiscal year 2010 and remains below 95
percent until the end of fiscal year 2014, at times falling to about 80
percent. See figure 1 for details.
(Fig 1 shows an 85% chance of sub-optimal performance through 2013)
--
Andrew Daviel, TRIUMF, Canada
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