Repositioned Galileo Satellite Declared Fit for Service

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PARIS — Tests of the European Galileo positioning, navigation and timing satellite recently moved from its initial bad orbit to an improved one have confirmed that it can be inserted into the broader Galileo constellation to deliver precision results to users, the European Space Agency announced Dec. 17.

The results are especially important for ESA and for the Galileo system’s owner, the European Union, because the satellite in question is the first of a contracted 22 so-called Full Operational Capability (FOC) spacecraft to be tested in orbit.

Galileo separation. Credit: ESA/J. Huart

The second FOC satellite, launched with the first into a useless orbit in August following a failure of the Europeanized Russian Soyuz rocket’s Fregat upper stage, is being guided into the same suboptimal but still-useful position as the first.

ESA said that in addition to tests of Galileo’s commercial service, the first FOC satellite was tested using the Public Regulated Service (PRS), which is Galileo’s highest-precision capability reserved for European military and other government use.

The navigation performance test of the FOC satellite was done with the four Galileo In-Orbit Validation spacecraft launched in 2011 and 2012. At least one of these satellites has lost partial functionality, including broadcast of the PRS signal, because of what ESA suspects is an antenna issue that will not affect the FOC satellites.

Gustavo Lopez Risueno, who heads the Galileo receiver group at ESA’s Estec technology center in Noordwijk, Netherlands, said the successful early tests of the FOC satellite suggest that its regular use within the planned 30-satellite Galileo constellation “is within reach.”

“In particular, it opens the door to its immediate use in combination with additional navigation message information provided through ground networks, which is a standard mode of operation for mass-market receivers such as those found in our smartphones,” Lopez said.

ESA officials are still grappling with whether mass-market receivers worldwide will be able to lock onto the two satellites in their unplanned orbit as quickly are able to find the rest of the constellation once it is launched.

The Galileo satellites were supposed to be launched into a circular orbit with an altitude of 23,222 kilometers. In the event, they were dropped off into an orbit with an apogee of 25,900 kilometers and — which is worse — a perigee of 13,713 kilometers. The perigee, with its daily exposure to the Van Allen radiation belt, combined with the orbit’s inclination relative to the equator left them unusable for Galileo.

The 11 firings of the first FOC satellite’s on-board thrusters required to raise the perigee by 3,500 kilometers left the satellite with enough fuel to function for 12 years, ESA estimates. ESA expects the same result from moving the second FOC satellite.

It is the European Commission, which is the executive arm of the 28-nation European Union, which will decide whether the two FOC satellites should be fully incorporated into the Galileo network.