[Satellite TODAY 12-20-10] Lockheed Martin Space Systems won a $1.3 billion contract modification from the U.S. Air Force to build the fourth Advanced Extremely High Frequency (AEHF) secure communications satellite, Lockheed Martin announced Dec. 15.
    The modification follows a $22 million contract awarded to Lockheed Martin by the Air Force in September 2009 to begin acquiring parts for AEHF-4.
The AEHF constellation will replace the current-generation Milstar satellites. AEHF-1, launched in August, experienced an on-board propulsion system failure that has prevented the satellite from entering service. The Air Force said special maneuvers were proceeding on schedule and that the satellite would reach its geostationary orbit between June and August.
    The second AEHF satellite has completed testing and is expected to be placed in orbit sometime in 2011. The Air Force plans to purchase at least two more AEHF satellites in the planned six-satellite constellation.