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Thirty-two GPS Satellites? Not Quite Yet ...
http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=492980
Feb 20, 2008
GPS World
It seems a healthy, 32-satellite GPS constellation isn't going to be
orbiting the earth just yet.
The U.S. military's GPS administrators sent out an advisory to GPS
users Tuesday stating that satellite SVN23, transmitting L-band code as
PRN32, would not be set to healthy as they had advised earlier this
month. The PRN32 designation is notable among other reasons because it
is the first time that the PRN32 designation will be used by an
operational, healthy GPS satellite -- and the first time there have
been 32 healthy birds in the air.
The U.S. Coast Guard Navigation Center advised GPS users Tuesday that
new data and time for setting SVN23 (PRN32) usable has not been
determined. But Air Force GPS operators suggested in Tuesday's Notice
Advisory to Navstar Users -- NANU, in military acronym parlance
-- that the satellite would be set to healthy in the near future.
When it is set to healthy, some older GPS receivers might not be able
to see it; GPS receivers initially were built to accommodate up to 31
satellite signals, and a PRN designated with the number 32 can't be
tracked by some manufacturers' devices that look for PRNs numbered 0
through 31. The U.S. Air Force began testing the PRN32 designation late
in 2006 -- while SVN23/PRN32 was set to unhealthy and not included
in the operational GPS constellation almanac, some all-in-view GNSS
tracking stations received the L-band signal.
As of January 2007, SVN23 has been broadcasting but set to unhealthy
and not included in the almanac. Nevertheless, a number of civilian
users have reported being able to track PRN32 since then.
