The cause of two Galileo satellites being released into the
wrong orbit August 22 can be traced to improper installation of a hydrazine fuel line, according to
Space News and the
GalileoGNSS blog.
The hydrazine fuel line was installed too close to a supercold helium line on the Fregat upper stage, which caused the hydrazine to freeze long enough to upset the Fregat stage’s orientation and cause the two satellites’ release into an orbit that is both too low and in the wrong inclination, officials said as reported on the websites.
No official report has been issued; the
board of inquiry is expected to release its findings this week.
The Euro-Russian inquiry board looking into the cause of the failure has discovered that one in four Fregat upper stages at prime contractor NPO Lavochkin in Moscow had the same fuel-line installation, according to the reports. “We have to assume that this was a practice that had gone on in perhaps a quarter of the Fregat stages produced in the past decade, but that it had not affected our launches up to now because of mission-specific aspects like coast time between burns, the number of burns and so on, which can influence the effect of the helium on the hydrazine,” one official is quoted as saying. “In any case, we’d like Arianespace, which currently has almost no inspection rights on the Soyuz, to be given more say in quality assurance.”
In the stages without the installation issue, the hydrazine and helium lines were separated so that the supercold helium could not freeze the hydrazine. The design did not foresee any problem in putting the lines together, but in fact that is a problem for some missions.
European Union government and officials are debating how to proceed, the reports said. The options are to continue, as scheduled, with the December launch of two more Galileo satellites aboard a Soyuz Fregat rocket, or to wait until next spring or summer and launch four Galileo satellites on a heavy-lift Ariane 5 vehicle.
As for the two wayward satellites, in a presentation to the 65th International Astronautical Congress in Toronto September 30,
OHB’s Galileo deputy program manager, Kristian Pauly, said he was optimistic that once the satellites’ perigee is raised and their orbit made less eccentric, they can be fitted at least partially into the Galileo program and perform a navigation function, Space News reported. OHB System is the prime contractor for the full operational capability (FOC) satellites.
The first priority, Pauly said, is to take the two satellites out of regular contact with the Van Allen belts and adjust their Earth sensors to their new, unplanned view of Earth — which is much closer given the lower altitude.
Pauly did not speculate on what the Galileo launch schedule would be. He said that OHB’s delivery schedule will not change much. “We have a delivery schedule that is extremely challenging and we will keep to it,” he said.
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