[maemo-users] FYI - possible GPS degradation in next few years

From: Andrew Daviel advax at triumf.ca
Date: Fri May 22 04:48:44 EEST 2009
"It is uncertain whether the Air Force will be able to acquire new 
satellites in time to maintain current GPS service without interruption."


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

More information about the maemo-users mailing list