The recently launched Block IIF satellite (SVN62/PRN25) is the first of...

Three's the Challenge
July 20, 2010
By: Oliver Montenbruck, André Hauschild, Peter Steigenberger, Richard B.
Langley
A Close Look at GPS SVN62 Triple-Frequency Signal Combinations Finds
Carrier-Phase Variations on the New L5

The recently launched Block IIF satellite (SVN62/PRN25) is the first of
a new generation of GPS satellites designed to transmit ranging signals
for civil users on three frequencies: the C/A-code on L1 at 1575.42 MHz,
the L2C-code on L2 at 1227.60 MHz, and the I5/IQ codes on L5 at 1176.45
MHz. Unlike L2, the L5 signal is located inside the protected
Aeronautical Radionavigation Services (ARNS) band, which makes it
specifically useful for safety critical aviation applications. In
combination with the legacy L1 signal, civil aviation users can now
perform ionospheric corrections without referring to the L2C signal.
Compared to L2C, the new L5 signal offers a much higher chipping rate
(the same as the encrypted P-code signal) of 10.23 MHz, which promises a
lower ranging noise and better multipath resistance. L5 signals have
already been transmitted for some time by the geostationary satellites
of the United States’ Wide Area Augmentation System (WAAS) and are now
about to become an integral part of the GPS constellation.

Following a short test transmission on June 17, 2010 (reported in the
July issue), the L5 signal was continuously activated on the morning of
June 28. According to GPS officials, the checkout of the satellite is
proceeding nominally and all signals have been found to fully comply
with specifications. This will allow the satellite to be set healthy as
soon as all commissioning tasks have been completed.

See:
http://www.gpsworld.com/gnss-system/gps-modernization/news/threes-challenge-10246?print=1