Thales Alenia Says Eutelsat W5’s Solar Array Motor is Malfunctioning

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  Space News Business

Thales Alenia Says Eutelsat W5’s Solar Array Motor is Malfunctioning

By PETER B. de SELDING
Space News Staff Writer
posted: 09 September 2008
09:54 am ET






PARIS
— Satellite manufacturer ThalesAlenia Space has determined that the Eutelsat W5 satellite in geostationary orbit above
Asia
has definitively lost the use of the drive mechanism that turns one of its two solar arrays. The failure will reduce the satellite’s planned 15-year service life by between one and three years, the company said Sept. 4.

Operated at 70.5 degrees east longitude and providing television and other communications links between
and
Europe
, the W5 satellite carries 24 transponders. Four of them have been taken out of service to compensate for the reduced power caused by the inability of one of the two solar arrays to orient itself toward the sun.

Cannes, France-based ThalesAlenia Space said a fifth transponder may need to be taken out of service during eclipse periods each year, when the spacecraft relies on the power stored in its batteries.

W5 was launched in November 2002. It features a bearing and power transfer assembly that is similar to the ones aboard the ThalesAlenia Space-built Arabsat-3A and Thaicom-3 satellites on which similar problems occurred in 2001 and 2003, respectively. The company had tentatively concluded that the Arabsat and Thaicom failures were not caused by the same problem, and that the Arabsat anomaly likely was due to a foreign object that caused a short circuit.

Thales
Alenia Space has since begun to build its own version of this system, known as a solar array drive assembly.

A solar array locked in a single position requires the satellite to expend more fuel during normal attitude-correction maneuvers that are conducted throughout a spacecraft’s operational life.

Thales
Alenia Space’s inquiry into the W5 issue has concluded that while it is likely that the satellite will expend more fuel as a result of the problem, it is impossible to say how much fuel will be needed in the coming years to compensate for the stuck solar array drive assembly.

The company said its best estimate is a loss of one to three years of service life.

Paris-based Eutelsat said in a Sept. 3 statement that W5 is expected to be retired in early 2014 rather than late 2018.

The company said the capacity lost on the satellite is not large enough to justify an impairment charge, and that it will not need to adjust the value of the W5 as it is carried on Eutelsat’s financial accounts.

Eutelsat
faced unusual public criticism of its decision to remove a New York-based television broadcaster, New Tang Dynasty Television, from W5 following the June onboard failure. A free-speech organization questioned whether New Tang Dynasty was removed because of a technical issue or because the broadcaster used W5 to beam programming sympathetic to the outlawed Falun Gong organization to its audience in mainland
China
. Eutelsat denied any political calculations and said its decision was based on technical considerations alone.