Updated Dec. 31 10:12 a.m. EDT

WASHINGTON — The U.S. Air Force has awarded Lockheed Martin Space Systems of Sunnyvale, Calif., a $116 million contract modification for launch support and related activities for the fourth in a series of highly secure military communications satellites, according to a Dec. 27 release from the Pentagon.

The money covers the fourth vehicle in the Advanced Extremely High Frequency (AEHF) constellation. Prelaunch planning and preparation traditionally begin about a year before launch, the announcement said. The fourth AEHF satellite is expected to launch in 2016 or 2017, Air Force officials have said.

Launch support activities include satellite shipment and related preparations, the launch campaign, launch, orbit raising and on-orbit testing, said Mark Lewis, a Lockheed Martin spokesman.

The satellites are used by Canada, the United Kingdom and the Netherlands in addition to the United States.

Lockheed Martin’s AEHF contract includes six satellites and associated ground systems and has an estimated value of $9 billion or more.

The third AEHF satellite was launched in September.

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