Updated Oct. 25 5:47 p.m. EDT

PARIS — A defective digital timing unit that forced four commercial broadband satellites to be pulled from launch preparations in September has now had the same effect on the Gaia star-mapping satellite owned by the European Space Agency (ESA), European government and industry officials said.

As was the case with the four satellites owned by startup operator O3b Networks, whose late-September launch aboard a Europeanized Soyuz rocket was scrubbed in the middle of the month, Gaia’s planned Nov. 20 liftoff has now been postponed.

The O3b satellites were subsequently returned to their manufacturer, Thales Alenia Space, where they have been undergoing tests at the company’s Rome facility following the prelaunch discovery of a signal anomaly in one or more of the four O3b satellites already in orbit.

Thales Alenia Space officials apparently discovered the cause of the problem, a digital clock used to create timing signals to downlink satellite telemetry, during the week of Oct. 14. The company sent out an alert to all its customers about the issue, including ESA, which on Oct. 22 elected to pull Gaia from the Soyuz launch manifest. 

While Gaia shares the timing component, the hardware’s location on the satellite makes it much easier to remove than is the case with the O3b spacecraft. Gaia therefore will remain at Europe’s Guiana Space Center spaceport on the northeast coast of South America while the defective timing-signal generator and the small box that houses it will be removed and returned to Italy for repair.

Thales Alenia Space officials did not respond to requests for comment.

In an Oct. 23 interview, Thomas Passvogel, head of projects at ESA’s science and robotic exploration directorate, said the component in question is fairly easy to remove from the Gaia satellite, and that returning it to Europe for repair is expected to take about four weeks. “We’re fortunate in that it’s not that deeply embedded” in Gaia, Passvogel said.

Once ESA is certain of when Gaia will be ready for launch, it will open negotiations with the Arianespace launch services consortium on a new launch date. Passvogel said Gaia’s next launch window opens on Dec. 17 and lasts for about three weeks, and that the spacecraft would be ready to launch on that day.

Gaia, whose mission is to map 1 billion stars in the Milky Way, cost some 940 million euros ($1.3 billion). 

For Evry, France-based Arianespace, the second consecutive 11th-hour cancellation of a Soyuz launch because of a satellite issue can only complicate a 2014 manifest that is already crowded.

The O3b issue has pushed the four satellites’ launch into early 2014, where it joins a list of payloads awaiting 2014 launch slots aboard the Europeanized Soyuz. Others include satellites for Europe’s Galileo positioning, navigation and timing constellation, which has suffered multiple delays.

O3b, based in Britain’s Channel Islands, has not yet announced a new launch date.

ESA, which is the technical manager of the Galileo project on behalf of the European Commission, told its ruling council the week of Oct. 16 that two Galileo satellites likely will be ready for launch in June. If that occurs, two additional pairs of satellites would be ready for launches before the end of the year.

ESA’s Sentinel-1A Earth observation satellite, which is also late, is slated for a Soyuz launch in 2014 as well. O3b, meanwhile, has another set of four satellites that had been moving toward a 2014 launch.

Pending confirmation of Gaia’s availability, Arianespace has only one launch planned before the end of the year. The heavy-lift Ariane 5 ECA rocket is scheduled to launch two commercial telecommunications satellites in mid-December.

Depending on the launch trajectories, Arianespace has said it takes about two weeks to realign its down-range tracking radars to prepare for a Soyuz launch after an Ariane 5 launch.

An Arianespace official said the Dec. 13 Ariane 5 launch date had been selected in part to give ground crews time to reconfigure the tracking radars following the Gaia launch. With Gaia having been pushed to the second half of December, the Ariane 5 — depending on the readiness of its two satellite customers — may be able to launch earlier.

That could enable Soyuz to launch Gaia at the beginning of its window and avoid having the Gaia and launch preparation teams working between Christmas and New Year’s.

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Europe’s Star-mapping Gaia Satellite Finally Launch Pad-bound

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.