ESA GALILEO: Satellite Recovered and Transmittting Navigation Signals

ESA's Galileo satellites are placed in medium orbits, at 23 222 km altitude along three orbital planes so that a minimum of four satellites will be visible to user receivers at any point on Earth once the constellation is complete. 

Credit: ESA

ESA’s fifth Galileo satellite, one of two delivered into a wrong orbit by VS09 Soyuz-Fregat launcher in August, has transmitted its first navigation signal in space on Saturday 29 November 2014.

It has reached its new target orbit and its navigation payload has been successfully switched on.

A detailed test campaign is under way now the satellite has reached a more suitable orbit for navigation purposes.

Recovery

The fifth and sixth Galileo satellites, launched together on 22 August, ended up in an elongated orbit travelling up to 25 900 km above Earth and back down to 13 713 km.

A total of 11 manoeuvres were performed across 17 days, gradually nudging the fifth satellite upwards at the lowest point of its orbit.

As a result, it has risen more than 3500 km and its elliptical orbit has become more circular.

“The manoeuvres were all normal, with excellent performance both in terms of thrust and direction,” explained Daniel Navarro-Reyes, ESA Galileo mission analyst.

“The final orbit is as we targeted and is a tribute to the great professionalism of all the teams involved.”

The commands were issued from the Galileo Control Centre by Space Opal, the Galileo operator, at Oberpfaffenhofen in Germany, guided by calculations from a combined flight dynamics team of ESA’s Space Operations Centre, ESOC, in Darmstadt, Germany and France’s CNES space agency.

The commands were uploaded to the satellite via an extended network of ground stations, made up of Galileo stations and additional sites coordinated by France’s CNES space agency.

Satellite manufacturer OHB also provided expertise throughout the recovery, helping to adapt the flight procedures.

Until the manoeuvres started, the combined ESA–CNES team 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.

In the new orbit, the satellite’s radiation exposure has also been greatly reduced, ensuring reliable performance for the long term.

ESA Galileo satellites 'Doresa' and 'Milena' on Payload Dispenser

The two Galileo FOC satellite 'Doresa' and 'Milena' are installed on the payload dispenser system. 

The two Galileo navigation satellites have been integrated on their payload dispenser system at Europe's Spaceport in Kourou, French Guiana. 

The pair will be mated atop a Soyuz Fregat upper stage and encapsulated in the protective payload fairing.

Galileo SATs 5-6 are scheduled to lift off at 12:31 GMT (14:31 CEST, 09:31 local time) on 21 August from Europe’s Spaceport in French Guiana on top of a Soyuz rocket. 

They are expected to become operational, after initial in-orbit testing, in autumn.


The two satellites will join the four Galileo ‘in-orbit validation’ satellites already in space. 

Launched in pairs in October 2011 and October 2012, these four satellites, the minimum required to obtain a position fix, served to demonstrate and validate the space and ground segments of the system.

Credits: ESA/CNES/Arianespace/Optique Vidéo du CSG - P Baudon