Arianespace Announces Cause of Galileo Launch Anomaly

Arianespace released the results of an investigation into why two European Union (EU) Galileo navigation satellites were left in the wrong orbit following a launch using Russia’s Soyuz rocket with Fregat upper stage.  The root cause was a “shortcoming” in the system thermal analysis of the Fregat design that led to freezing of the hydrazine fuel.

The conclusion was reached by an Independent Inquiry Board established by Arianespace after the August 22, 2014 anomaly.  The two Galileo satellites, intended to be the first of the Full Operational System, were stranded in an orbit that renders them unable to perform their primary mission.  The inquiry Board was led by Peter Dubock, former Inspector General of the European Space Agency (ESA).  The EU is funding the Galileo navigation satellite system, which is similar to the U.S. Global Positioning System (GPS).  ESA is the EU’s design and procurement agent for Galileo.  The EU plans to have 30 operational Galileo satellites in orbit by the end of the decade.

Arianespace launches Russia’s Soyuz rocket from its launch site in Kourou, French Guiana, through a partnership with Russia’s space agency, Roscosmos, and two Russian manufacturers — RKTs-Progress, which builds Soyuz, and NPO Lavochkin, which builds the Fregat upper stage.  

At first, the August 22 launch seemed to go fine, but the satellites were later discovered in the wrong orbit.  The Arianespace inquiry drew on data supplied by its Russian partners and its findings “are consistent with” a separate board of inquiry appointed by Roscosmos.

The Soyuz rocket was exonerated and found to have performed as planned.   The problem was in the Fregat upper stage because the hydrazine fuel froze and blocked the fuel supply to the Fregat’s thrusters.  The fuel froze because the hydrazine and cold helium feed lines were connected by the same support structure, creating a thermal bridge.  The root cause was found to be “ambiguities” in the design documentation as the result of poor system thermal analysis in the design phase. 

Arianespace concluded that the issue is easy for Lavochkin to resolve and launches could resume as early as December 2014.  The company also noted that this failure followed 45 consecutive successful uses of the Fregat.