The US Navy has exercised a $339.6m contract option for Lockheed to build a fifth satellite in the Mobile User Objective System (MUOS) constellation.

MUOS will replace the current Ultra High Frequency Follow-On (UFO) system and provide assured communications, including simultaneous voice, video and data, for mobile warfighters.

Lockheed vice president and MUOS program manager Mark Pasquale said the MUOS will provide 10 times more communications capability than the current UFO satellite system.

The first MUOS satellite is currently undergoing thermal vacuum testing to verify spacecraft functionality and performance in a vacuum environment and is scheduled for delivery in mid-2011.

The second satellite will undergo environmental testing of the fully integrated satellite in preparation for delivery in 2012.

Lockheed Martin Space Systems is the prime contractor and system integrator, and the team includes GD C4 Systems and Boeing Defense, Space and Security.