ESA explains failing atomic clocks in Galileo satellites
Space agency ESA has explained about the failing atomic clocks on board the Galileo satellites. The organization suspects that the rubidium clocks have failed as a result of a short circuit, possibly due to a design flaw.
In recent months, three rubidium clocks have failed on Galileo-FOC satellites, ESA writes on its website. According to research by the European Space Agency, there are similarities with those three defects and it is probably a short circuit. The short circuit is said to be related to a certain test procedure that is performed while the atomic clocks are still on the ground. Research has revealed “potential weaknesses” in the design of the rubidium clocks, according to ESA, but the exact cause has not yet been determined. The investigation therefore continues.
While the investigation is still ongoing, the ESA and equipment suppliers agree that “some adjustments” are required to the 16 rubidium clocks in the eight satellites yet to be launched. ESA expects the risk of failure for the remaining 33 rubidium clocks, already in orbit, to be less. Different test procedures were used for those atomic clocks.
In addition, six hydrogen maser clocks have malfunctioned in the past two years. This concerns five copies on Galileo IOV satellites and one clock from an FOC satellite. ESA points to two causes: the first is ‘a small margin of error with a certain parameter’ and two clocks have failed as a result. The other cause is that when a hydrogen maser clock is turned off for a long time, it sometimes fails to start up. As a result, four clocks no longer work.
Rubidium clock and hydrogen maser clock
Thirty working hydrogen maser clocks are still present in the Galileo satellites. ESA says it is studying procedures to significantly reduce the risk of defects. This should yield results within a few weeks. This involves adjustments to the hydrogen maser clocks on the eight satellites yet to be launched.
Whether adjusting the atomic clocks will affect the satellite launch schedule is still under investigation. The ESA says it is confident that the two planned launches for 2017 and 2018 will go ahead as planned. The Galileo navigation system should be fully operational by 2020 and will consist of 30 satellites, of which 6 are reserves.
On Wednesday, the news came that the ESA is struggling with nine failing atomic clocks on its satellites for the Galileo navigation system. Each satellite has four atomic clocks on board, two of each type. To function, the satellites only need one clock, the rest is there as a backup. As a result, the defects have not yet affected the operation of the system.