ESA GIOVE-B: Maser Atomic Clock ticking

Three years after ESA’s Galileo prototype GIOVE-B reached orbit, the passive hydrogen maser at its heart is still ticking away as the most precise atomic clock ever flown in space for navigation – that is, until the first Galileo satellites join it later this year.

Launched by Soyuz rocket from Baikonur in Kazakhstan on 27 April 2008, GIOVE-B was ESA’s second Galileo In-Orbit Validation Element satellite to fly. The first, GIOVE-A, made it to orbit on 28 December 2005.

The satellites had the same goals: secure the radio frequencies provisionally allocated to Europe’s Galileo satnav system by the International Telecommunications Union, gather data on the radiation environment of medium Earth orbit, and validate key Galileo payloads in orbit.

	Hydrogen maser clock

“GIOVE-B has now been in orbit for 36 months, nine months more than its nominal lifetime,” said Valter Alpe, overseeing GIOVE operations for ESA.

“Both satellites are still working well. GIOVE-A has reached 64 months in orbit. This longevity is partly due to an unusually mild solar cycle, but also reflects well on the operating margins built into their design.

“Most notably, GIOVE-B’s passive hydrogen maser – Europe’s main technological advance for Galileo – is still operating as precisely as planned.

We haven’t experienced any real surprises. As a result, much the same design is being used for the operational Galileo satellites.”

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