The second of the two Galileo satellites stranded in a useless orbit due to a launch fault has reached a target position that will allow it to serve at least some of its intended purposes.
Concluding a six-week recovery operation, controllers at the European Space Agency (Esa) confirmed the satellite is now circling the Earth in an elliptical orbit with the lowest point at about 17,000km, which would allow them to test the navigation payload.
“I am very proud of what our teams at Esa and industry have achieved,” said Marco Falcone, head of Esa’s Galileo system office. “Our intention was to recover this mission from the very early days after the wrong orbit injection. This is what we are made for at Esa.”
The sixth satellite of Europe’s global navigation satellite system Galileo was injected into a wrong orbit together with its sister satellite last August by a malfunctioning Soyuz rocket.
The incident left the two spacecraft circling the Earth on an ellipse with the highest point at 25,000km and the lowest at only 13,000km above the Earth’s surface. The indented operational orbit of the Galileo constellation is circular at the altitude of 23,500km.
To save the two satellites, Esa together with the French aerospace centre CNES devised an elaborate plan to raise the lowest point of the orbit and make it more circular.
The procedure was tested on the fifth Galileo satellite, which entered the corrected position at the end of November 2014.
Esa said the recovery operation required the controllers to perform seven complex manoeuvres.
The two satellites are now orbiting on mirror trajectories, which place them on opposite sides of the planet.
The orbit correction will allow the two spacecraft to revisit the same location above the Earth’s surface every 20 days compared to the standard Galileo repeat pattern of 10 days. Esa said the revisit time is sufficient for the spacecraft to synchronise their ground tracks with the rest of the constellation.
The manoeuvre also took the two spacecraft out of the heart of the Van Allen radiation belts, which threatened the satellites’ durability.
While tests on the fifth satellite already proved the payload performs correctly, tests on the sixth spacecraft are about to commence.
The decision, whether the spacecraft will be used for navigation and search-and-rescue purposes will be ultimately taken by the European Commission, who owns the constellation.
The next pair of satellites is due for launch on 27 March.