MUOS 2 encapsulated prior to launch in 2013. Photo: Lockheed Martin

[Via Satellite 04-11-2016] United Launch Alliance (ULA) is delaying the Atlas 5 launch of the Mobile User Objective System 5 (MUOS 5) satellite indefinitely due to ongoing evaluation of a first stage anomaly experienced during the OA-6 mission.

On March 22, ULA successfully delivered the OA-6 Cygnus spacecraft to the International Space Station (ISS), but the launch system experienced a premature first stage shutdown, cutting off approximately 6 seconds early. The Atlas 5’s Centaur upper stage automatically compensated by burning longer, delivering Cygnus to a precise orbit as planned, but what caused the first stage shutdown remains unclear.

The ULA engineering team is continuing to review the data and has developed initial fault trees with industry partners. The team has isolated the anomaly to the first stage fuel system and its associated components. ULA and its partners are assessing all flight and operational data to determine root cause and identify appropriate corrective actions prior to future flights.

The MUOS 5 spacecraft and launch vehicle are secure at their processing facilities.