ESA wants to know why Galileo satellites' clocks stopped working

Because satellite navigation systems need precise atomic clocks to work properly.


Something strange is going on with the Galileo satellites, and the European Space Agency wants to find out what's causing it. Apparently, ten atomic clocks on board five of the 18 navigation probes already in orbit have malfunctioned, and it could force the agency to delay the scheduled launch of four more satellites in August. Satellite-navigation systems like ESA's Galileo need highly precise atomic clocks to work properly, since they have to broadcast their signals at the same time. Broken clocks will hinder Galileo's ability to "deliver real-time positioning accuracy down to the meter range" like the ESA promised.

Three of the devices hit by the mysterious affliction are rubidium atomic frequency clocks, while the rest are more-precise passive hydrogen maser variants. One of the hydrogen devices has been restarted, bringing the total number down to nine. Since each satellite carries four clocks and none of them have more than two broken devices, Galileo still works. According to Space, the agency thinks the clocks short-circuited and failed because they're switched off for long periods. However, it still needs to investigate the event further to make sure the rest of the clocks won't get affected.

The Galileo constellation was supposed to be up and running back in 2008 but was plagued with delays. While it currently has 18 satellites, it will ultimately be composed of 24 with six spares if everything goes well. For now, the agency plans to examine and refurbish the clocks aboard the four satellites scheduled to launch in August to prevent their untimely deaths.