GPS PRN32 giving problems

Some older GPS receivers are having problems with GPS satellite PRN32 - particularly some marine navigation receivers used by Automatic Identification Systems (AIS).

The problem - highlighted in earlier news - stems from the older receivers' non-compliance with the GPS interface standard, IS-GPS-200. They use a 5-bit digital stream to recognise each satellite's allocated pseudo-random noise (PRN) code - this covers PRNs 00 to 31, but not the newly-allocated PRN32.

On 26 February, GPS satellite SVN23 began transmitting L-band code as PRN32.

Affected systems are reported to include Saab R3 Class A AIS, Northrop Grumman Sperry R3 Class A AIS, and the Northrop Grumman Sperry Navigation Heading Compass.

Saab have confirmed that it had received reports that its R3 transponders and R30 base stations were having problems.

The company said it has been able to correct the problem in a laboratory environment, and is working on a software upgrade for field use. In the meantime, it has outlined a series of steps on its website that users of older equipment can take to minimize the problem.

Details from GPS World