The U.S. Air Force and Lockheed Martin have shipped the second in the service’s series of highly secure communications satellites to Cape Canaveral Air Force Station, Fla., in preparation for a scheduled April 27 launch.

The Advanced Extremely High Frequency (AEHF)-2 satellite arrived from California Feb. 13, the Air Force said in a Feb. 23 press release. The satellite will undergo 75 days of preparation before being launched to geostationary transfer orbit atop a United Launch Alliance Atlas 5 rocket, the Air Force said.

Sunnyvale, Calif.-based Lockheed Martin Space Systems is under contract to build four AEHF satellites, which are designed to provide assured and highly secure communications links under all conditions, including a nuclear war environment. Northrop Grumman Aerospace Systems of Redondo Beach, Calif., provides the satellites’ communications payloads.

The Air Force is expected to order two more AEHF satellites this year.

The first AEHF reached geostationary orbit late last year, more than a year after it was launched. Its arrival to its operating position was delayed by an onboard propulsion glitch that forced the Air Force and Lockheed Martin to devise a new orbit raising plan.