Lockheed Martin Space Systems of Sunnyvale, Calif., has delivered the first of a new generation of highly secure military communications satellites to Cape Canaveral Air Force Station, Fla., in preparation for a scheduled July 30 launch on an Atlas 5 rocket, the company announced May 24.

The Advanced Extremely High Frequency (AEHF) constellation will replace the U.S. Air Force’s Milstar communications satellites, over which the most sensitive and critical military signals travel. Lockheed Martin is under contract for three of the spacecraft, with a contract for the fourth satellite expected this summer, company officials have said.

AEHF was originally planned to be a constellation of three satellites, to be followed by the next-generation Transformational Satellite, or T-Sat, communications system. Cost estimates for T-Sat reached as high as $26 billion for the life of the program, and the Pentagon canceled it in 2009. The Air Force now plans to buy a total of six AEHF craft, some of which may incorporate some next-generation technologies developed under the T-Sat program.

The second and third AEHF satellites are planned to be launched eight and 16 months after the first craft.