Europe’s fifth Galileo satellite, one of two delivered into a wrong orbit in August 2014, has transmitted its first navigation signal.
The fifth and sixth Galileo satellites, launched together on 22 August 2014, ended up in an elongated orbit travelling up to 25,900 km above Earth and back down to 13,713 km. The combined team from the European Space Agency (ESA) and France’s CNES space agency initially maintained the satellites pointing at the Sun using their gyroscopes and solar sensors. This kept the satellites steady in space but their navigation payloads could not be used reliably. The fifth Galileo satellite has now been moved to a more suitable orbit following 11 manoeuvres performed across 17 days, gradually pushing the satellite upwards at the lowest point of its orbit. As a result, it has risen more than 3,500 km and its elliptical orbit has become more circular.
The revised, more circular orbit means the fifth satellite’s Earth sensor can be used continuously, keeping its main antenna oriented towards Earth and allowing its navigation payload to be switched on. Significantly, the orbit means that it will now overfly the same location on the ground every 20 days. This compares to a normal Galileo repeat pattern of every 10 days, effectively synchronising its ground track with the rest of the Galileo constellation. After the fifth satellite reached its new target orbit, the navigation payload has been successfully switched on and a detailed test campaign is now under way. The same recovery manoeuvres are planned for the sixth satellite, taking it into the same orbital plane but on the opposite side of Earth. The decision whether to use the two satellites for Navigation and SAR purposes as part of the Galileo constellation will be taken by the European Commission based on the test results.
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