The independent inquiry board tasked with identifying the cause of the anomaly in the August 22, 2014 launch of the two satellites of the Galileo constellation announced its findings. The unofficial news that came at the end of September, which blamed a malfunction in the rocket’s Fregat upper stage. The freezing of the hydrazine used as a fuel resulted in the inability to insert the satellites in their correct orbit.

In the days following the launch, Arianespace, which managed it on behalf of ESA, created an independent inquiry board together with the Agency and the European Commission. Initially, the launch appeared to succeed but in the following hours the two satellites of the Galileo constellation, the European alternative to the GPS system, were found in a orbit different than the planned one.

The inquiry board established that the Soyuz rocket worked properly and that’s the reason why until the end everything seemed to go well. The problem has been identified in the Fregat upper stage, the one used for the last maneuvers required for a satellite to enter its correct orbit or even to an interplanetary probe to be inserted into the path to its destination.

The Fregat is versatile and can be used in various configurations, depending on the needs. In the case of the launch of the Galileo satellites the Fregat-MT version was used but the board found a design problem that caused the malfunction on that occasion.

A cold helium feed line passes near a hydrazine line and they’re connected to the same support structure, which became a thermal conductor. The result was that the hydrazine was cooled so much that it froze and two thrusters ceased functioning. The consequence was an error in the orientation of the Fregat and then the insertion of the two Galileo satellites in an incorrect orbit.

The proximity of the helium and hydrazine feed lines is present in other Fregats because the thermal conduction of the support structure was overlooked. This type of problem had never happened previously because it depends on various factors such as the number of thruster burns and the time between burns.

According to the inquiry board, the problem can be solved easily and quickly. For this reason, it should be possible to proceed with a new launch in December 2014, which should be again on a Soyuz carrier rocket with a Fregat-MT upper stage. There’s still the problem of the two satellites in the wrong orbit.

The first assessments made after the launch made ​​it clear that it would be impossible to move the two Galileo satellites in their planned orbit. The biggest problem is that their orbit is very eccentric and brings them to within the van Allen belts, where radiation is very high. Although they were designed to withstand radiation, continuous exposure to such high levels will reduce their life.

At the end of September, at the 65th International Astronautical Congress, Kristian Pauly, one of the managers of OHB AG, one of the Galileo project’s contractors, stated that he was optimistic about the possibility of adjusting at least in part the satellites’ orbit. Making it less eccentric orbit, it may be possible to use them. It would be quite an achievement!

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