Clocks fail on some Galileo satellites, backups working

Clocks have failed onboard several Galileo satellites in space, reports Phys.org, a web-based science, research and technology news service.

The cause of the failure is being investigated, European Space Agency director general Jan Woerner told journalists in Paris on Wednesday.

Each Galileo satellite has four atomic timekeepers — two rubidium and two hydrogen maser. Three rubidium and six hydrogen maser clocks are not working.

Passive hydrogen maser atomic clock of the type flown on Galileo, accurate to one second in three million years. (Photo: ESA)

The rubidium devices are similar to those used on current GPS satellites. The more precise hydrogen maser instruments were designed to give Galileo superior performance to the American GPS network.

Five of the maser failures have occurred on the satellites that were originally sent into orbit to validate the system, but all three rubidium stoppages are on the spacecraft that were subsequently launched to fill out the network, reports BBC News.

Each orbiter needs one working clock for the satellite navigation to work, with the other three clocks being spares. As of mid-January, 10 Galileo atomic clocks, the key element in a navigation satellite, had failed on four different satellites. One was recently returned to service, leaving nine outages, reports Space Intel Report.

Initial services were launched in December, and the failure of nine clocks out of 72 launched to date has not affected operation, Woerner said.

“If this failure has some systematic reason we have to be careful” not to place more flawed clocks in space, Woerner said. The question now is “should we postpone the next launch until we find the root cause?”

The next four satellites were to have been launched in August-September, but the launch has been postponed for November or December to investigate the clock failures. “You can say we wait until we find the solution, but that means if more clocks are failing then we are reducing the capability of Galileo,” Woener said.

The failures have occurred on two satellite platform designs: one built by Airbus and Thales Alenia Space as part of a four-satellite system validation program, and the other by Galileo prime contractor OHB SE of Germany, reports Space Intel Report. This is complicating the analysis to determine the cause of the failures.

Eighteen orbiters have been launched for the Galileo constellation to date, a number that will ultimately be boosted to 30 operational satellites and two spares.