GPS Modernization and the L5 Signal

One of the most significant additions among the raft of changes that are being made to the GPS system is the addition of a second safety-of-life signal for civilian use. This new L5 signal is centred at 1176.45MHz in the worldwide Aeronautical Radio-navigation Services band, and will be broadcast at roughly twice the power of the existing L1 and L2C signals. It also features wider bandwidth and longer spreading codes, and will be particularly useful for enabling aircraft to make precision landings in high multipath environments as well as reducing errors due to the ionosphere.

The first of the new constellation of satellites capable of broadcasting the L5 signal, the GPS IIR-20(M), was launched from Cape Canaveral Air Force Station, Florida, on 23rd March 2010, and began broadcasting the L5 signal on 10th April 2010. But while this satellite will serve as ample proof of concept, the full L5 signal coverage will not be available until the GPS modernisation is complete, which is unlikely before 2013.

However, designers of equipment can prepare for GPS modernisation by simulating all the new signals today using Spirent's range of GNSS simulators. Not only do these instruments cover the new L5 signal, as defined in the new ICD-GPS-705 standard, they also cover all the other enhanced signals that will be provided by the new modernised GPS constellation. Beyond GPS, they also cover all signals for the GLONASS and Galileo GNSS’s as well as the regional and local augmentation systems.

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