05 November 2008

L2C navigation message coming soon

The GPS Wing announced the availability of the GPS new navigation message on L2C in autumn 2009. "In the fall of 2009, the U.S. Air Force will achieve another milestone on the path toward GPS modernization. Operators at the 50th Space Wing and the 2nd Space Operations Squadron will upload new software to the IIR-M satellites enabling the first broadcast of a transitional Civil Navigation (CNAV) message on the already transmitted second civil signal (L2C). Once the go-ahead is given, the new message will broadcast on the L2C signal emanating from the IIR-M satellites. With the upcoming launches of the remaining two IIR-Ms, there will be a total of eight modernized GPS satellites broadcasting L2C with the new CNAV message. Additionally, the IIF satellites will be launched with the built-in capability to broadcast the new message. ... he L2C signal will provide a lower tracking threshold and better cross-correlation protection than L1 C/A. The data portion of the L2C signal is also different; instead of the current "legacy" navigation (LNAV) structure with subframes of data repeating in a fixed pattern as on L1 C/A, the CNAV structure which will be used on L2C has individual messages which can be broadcast in a flexible order with variable repeat cycles."