Update on SVN23/PRN32

John Owen kindly corrected my last email concerning the use of PRN32 in his email that follows this one. GPS has used PRN32 once before on an operational satellite. I asked the GPS Operations Center and have been told that PRN32 was used between 1992 and 1993 and then it was changed to a different PRN after it was discovered that some receivers at that time interpreted the PRN as 00.

This history is in part why the United States Air Force GPS Wing issued an open memorandum over a year ago (September of 2006) to the GPS community. CGSIC distributed the memorandum to all of our membership at the time and the following link is to a copy of the memorandum. 


The issue was also discussed at the last CGSIC meeting at Fort Worth Texas during September of 2007. 

My thanks to John Owen for correcting my omission of the use of PRN32 in the 1990s.  It gives me the opportunity to stress to the CGSIC membership the importance of advising your associates in the GPS community to report any GPS receiver issues with PRN32 when it is placed operational next week. Roughly 15 years has passed since PRN32 was last broadcast and during that time much effort has been made in providing notification to the GPS manufacturers and users that PRN32 may be used in the future. However, there are probably many users who do not subscribe to NAVSTAR Advisory Notice to Users (NANUs) or participate in CGSIC. 

As stated in the NANUs, civil GPS users should report GPS outages or problems to the Navigation Center (NAVCEN). The preferred way to make a report is by internet using the "GPS report-a-problem" link located on the following NAVCEN website page:


A report can also be made by calling the Navigation Information Service
24 hour phone number (703-313-5900).