WASHINGTON — United Launch Alliance’s Atlas 5 rocket returned to flight June 24 with its first launch in three months to successfully lift the fifth and final satellite in the U.S. Navy’s next-generation mobile communications system.
The launch completes the Navy’s next-generation narrowband communications constellation, known as the Mobile User Objective System, which includes four satellites and an on-orbit spare that provide smartphone-like communications to mobile forces at rates 10 times faster than the legacy system.
The MUOS-5 satellite launched aboard an Atlas 5 rocket from Cape Canaveral Air Force Station, Florida, at 10:30 a.m. local time. The Atlas 5 configuration used in the launch featured a 5-meter payload fairing, five solid-fueled strap-on boosters and a Centaur upper stage powered by a single RL-10 engine.
Tory Bruno, ULA’s chief executive, confirmed the successful launch on Twitter at 1:36 p.m. The Navy said June 24 the satellite will take several days to reach its destination in geosynchronous orbit.
The launch also marked a return to flight for the Atlas 5 following an anomaly during a March 22 launch of a Cygnus cargo spacecraft to the International Space Station. Then, ULA said the Atlas 5 experienced an “unexpected shift in fuel pressure differential” across a mixture ratio control valve in the RD-180 engine, about four minutes after liftoff. The change caused the engine to run oxidizer-rich, depleted the supply of liquid oxygen and shut down the engine prematurely, even though there was still “significant fuel” left on the first stage.
While ULA has stressed that it considered the March 22 launch a successful mission after it placed the Cygnus cargo spacecraft into its planned orbit, the company also sought to make changes to avoid the anomaly in the future.
ULA said the engine supplier, NPO Energomash, made a minor change to the valve and that the fix has been verified in hot-fire tests.
The delay in launching MUOS is not expected to have any long-term impact on ULA’s manifest. The company still expects to launch nine more times by the end of 2016. ULA’s next launch is a mission for the National Reconnaissance Office, dubbed NROL-61, aboard an Atlas 5 on July 28.
ULA launched the first MUOS satellite in February 2012. The next three went up on Atlas 5 launches between July 203 and September 2015. All five satellites were built by Lockheed Martin Space Systems of Sunnyvale, California.