Galileo quartet – what stage are the satellites at now?

30 January 2018
The satellites are currently in the correct orbit and are drifting to their final slots. ©ArianeSpace

Six weeks ago, four new Galileo satellites were successfully launched from the European spaceport in Kourou, French Guiana. A lot has happened since then, as the satellites move towards their final orbit and prepare for the first transmission of navigation signals.

At exactly 19:36:08 CET on December 12, an Ariane 5 rocket lifted-off from Kourou carrying four Galileo satellites: Nicole, Zofia, Alexandre, and Irina. Four hours later, the satellites established first contact with Earth, unfolded their solar panels and reached a stable configuration. However, the story does not end there, as the satellites go through a number of crucial stages between their launch and reaching their final position.

Days after their launch, the four satellites transited from sun acquisition mode to Earth tracking mode, also called nominal operational mode (NOM), where they point to the Earth and all antennas are orientated towards the ground. After transition to NOM, the satellites began moving up to Galileo orbit, and Nicole and Zofia made the first and second manoeuvres.

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Nicole was first to finish all of its manoeuvres and control of the satellite was transferred from the EOP team in Toulouse to the Galileo Control Centres in Fucino and Oberpfaffenhofen, leaving the remaining three satellites under the control of the EOP team. At this stage the launch NAGU was published on the GSC website. Then, control of Zofia was transferred to the Galileo Control Centre and Alexandre and Irina started their manoeuvres - control of these satellites was later transferred to the GCC.

What next?

The four satellites are currently in the correct orbit and are drifting, in pairs, to their final slots. As soon as they reach their final position, they will be ready to start payload testing. After payload testing starts, it will still be several months before the satellites go into service.

GSA oversees EOP

This launch was the first mission in which the European GNSS Agency (GSA) was responsible for the Early Orbit Phase (EOP). GSA worked hand-in-hand with ESA, responsible for the launch phase, oversaw Spaceopal (joint venture between Telespazio and DLR-GfR) in their new role as Galileo Service Operator, and French Space Agency (CNES)- responsible for EOP operations. The EOP is one of the most important phases of a space mission as it positions the spacecraft into the correct orbits after launch, and gradually switches on and tests the first satellite elements.

The EOP activities were led by a team of specialists from GSA which oversaw the operations teams of Spaceopal and CNES. EOP operations were conducted from a dedicated control room in the CNES Centre Spatial de Toulouse, from which the team monitored and controlled all of the main EOP stages.

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Updated: Feb 01, 2018