How engineers rescued two lost satellites from a faulty orbit
In short: In August, two Galileo satellites were launched into the wrong orbit by a Soyuz-Fregat launcher. They were considered lost, but a massive international effort has successfully nudged them back toward their intended mission, turning a potential failure into a triumph of precision engineering.
The crisis began in August when the VS09 Soyuz-Fregat launcher delivered Europe's fifth and sixth Galileo satellites into an incorrect, elongated orbit. Instead of their target, they were traveling in an elliptical path that swung between 13,713 km and 25,900 km above Earth. Because of this instability, the satellites' navigation payloads could not be used reliably, though teams managed to keep them steady by pointing them toward the Sun using gyroscopes and solar sensors.
Recovery required a complex, 17-day campaign involving 11 precise maneuvers. Guided by flight dynamics teams from ESA’s Space Operations Centre in Darmstadt and France’s CNES, the Galileo operator, Space Opal, issued commands from Oberpfaffenhofen, Germany. These maneuvers, performed at the lowest point of the orbit, gradually nudged the fifth satellite upward by more than 3,500 km, transforming its elliptical path into a more circular one.
The success of these maneuvers changed the mission's outlook. By reaching a more suitable orbit, the fifth satellite's Earth sensor could be used continuously to orient its antenna toward Earth. This allowed the navigation payload to be switched on, with the first signal successfully transmitted on Saturday, 29 November 2014. Furthermore, the new orbit significantly reduces radiation exposure, ensuring the satellite's long-term reliability. The satellite will now overfly the same ground location every 20 days.
This recovery was made possible through a coordinated effort between ESA, CNES, and the satellite manufacturer OHB, who helped adapt the necessary flight procedures.
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Sources
- Summary by Intellect · source: Galileo satellites recovered
- Also: Galileo satellite recovered and transmitting navigation signals
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