U.S. Air Force officials are preparing to launch the second Boeing GPS IIF satellite on July 14.

The launch window opens at 2:49 a.m. EDT at Cape Canaveral, says Col. Christopher Warack, space systems program manager at the Space and Missile Systems Center near Los Angeles.

The satellite, SVN-63, will be boosted by a Delta IV using two solid-rocket motor strap-on boosters as well as a 4-meter payload faring. The GPS IIF satellite, made by Boeing, will be lifted 11,000 mi. into a circular orbit after three upper-stage burns, says Jim Sponnick, vice president of mission operations at United Launch Alliance.

The first GPS IIF satellite was launched in May 2010 and is providing “excellent atomic clock performance,” Warack says. It is one of 31 GPS satellites of various configurations transmitting precision timing and location signals to users today.

Though the first GPS IIF satellite is operational, its M-code (strong, military-specific), L2C and L5 signals are still being worked on and the M-code signal is now switched off, according to Warack. “There is no question whether the satellite will meet its requirements,” Warack said during a teleconference with reporters July 5. The issue has been continuing to explore the amount of margin in the power level for the M-code signal, he says.

The receivers needed to use the new M-code have not yet been fielded, and the capability will not be added until elements of the new Raytheon-built GPS operational control segment are fielded in 2016.

Warack says the Air Force is experimenting with different power levels for the M-code signals to “make sure we are operating the satellites optimally.”

The government notified users in April that the M-code would be switched off.

An industry official says Boeing has developed optimized transmitter settings to address the signal issue.

The second GPS IIF was built by Boeing at a loss owing to manufacturing problems. The Air Force is expected to buy a total of 12 satellites, and Boeing has established a pulse production line to more efficiently build the spacecraft.

Meanwhile, Lockheed Martin has completed its systems design review for the GPS IIIB program, the second increment of next-generation satellites in the constellation. Lockheed is developing the GPS III family, with the first IIIA slated for launch in 2014.