14 DAY TRIAL // Officials with the European Space Agency (ESA) are delighted to announce that a passive hydrogen maser installed aboard a trial satellite has reached an impressive milestone, having already spent more than 3 years in Earth's orbit.
The instrument, which is in essence the most precise atomic clock ever flown to space, is installed aboard the GIOVE-B prototype. This is a satellite that was constructed to test technologies which will fly on the Galileo spacecraft.
The latter are the European Union';s response to the American-built Global Positioning System (GPS). It will provide the same type of services, except with significantly higher accuracy.
At the same time, Europe will have access to more precise data. At this point, the US is imposing a precision limit on the GPS data it supplies to every other nation through its orbital positioning system.
The first Galileo satellites aren't scheduled to fly until later this year, but ESA already has the GIOVE-A and GIOVE-B demonstrators in orbit for years. Their main cargoes are the advanced atomic clocks that will enable Galileo to be so precise.
“GIOVE-B has now been in orbit for 36 months, nine months more than its nominal lifetime. Both satellites are still working well. GIOVE-A has reached 64 months in orbit,” says the ESA overseer of GOCE operations, Valter Alpe.
“This longevity is partly due to an unusually mild solar cycle, but also reflects well on the operating margins built into their design,” the official adds.
“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,” he goes on to say.
GIOVE-B, short for Galileo In-Orbit Validation Element satellite, was the second spacecraft of the validation series to fly. It took off from the Baikonur Cosmodrome in Kazakhstan on April 27, 2008, aboard a Soyuz delivery system.
It is also the first satellite ever to carry a passive hydrogen maser (PHM). This particular atomic clock has an accuracy of one second in three million years, ESA explains. For comparison, GIOVE-A has a rubidium atomic clock that is precise within 3 seconds in a million years.
On the actual Galileo satellites, both types of clocks will be installed together. However, only the PHM will be on during routine operations, with the rubidium one acting as a back-up.