WASHINGTON — The fifth production satellite in the U.S. Navy’s next-generation mobile communications system is completing its final testing, according to an Aug. 4 press release from the program’s prime contractor, Lockheed Martin Space Systems of Sunnyvale, California.

The satellite, referred to by the Navy as Mobile User Objective System-4, is expected to launch in summer 2015.

Lockheed Martin put a production rush on the fourth and fifth MUOS satellites after a soldering problem delayed production of the third in the program. The Navy also shuffled the launch order of the satellites, moving the fourth and fifth satellites ahead of the third, which the service now refers to as MUOS-5.

The first and second MUOS satellites were launched in February 2012 and July 2013, respectively; MUOS-3 now in final checkout, is scheduled to launch in January 2015. The MUOS-5 satellite, which Lockheed Martin still refers to as production vehicle No. 3, is slated to launch in 2016.

The MUOS constellation is designed to provide smartphone-like communications to mobile U.S. forces as well legacy mobile services at rates 10 times faster than the legacy system.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.