Ariane 5-Flying the fantastic four


Separation will mark the start of a set of critical activities and manoeuvres to ensure the four Galileo sats are ready for handover by the 'CNESOC' team to the Galileo Control Centre the rest of their mission

Quad sats see space

8 November 2016This month, a single Ariane 5 rocket is set to propel four Galileo satellites into orbit for the navigation constellation’s first-ever quadruple launch. Mission controllers are training intensively for the complex space delivery.

On 17 November, an Ariane 5 will use a new payload dispenser to release four identical satellites into orbit in one go.

This will be the eighth Galileo launch, and will bring the number of satellites in space to 18. Once complete, the system will sport 24 operational satellites and a ground network to provide positioning, navigation and timing services.

To date, Soyuz rockets have carried two satellites at a time. This quadruple launch presents several technical challenges, including the new dispenser and the need to establish control over four independent satellites almost simultaneously.

Four times complex mission control

The ascent into the medium-altitude orbit will take three and a half hours. Then, after the satellites separate, a combined team from ESA and France’s CNES space agency will take over, establishing control and shepherding them through their early orbits, lasting nine days for one pair and 13 days for the other.

The joint ESA/CNES mission control team works, alternately, from here and from ESOC, in Darmstadt, Germany, to oversee the critical launch and early orbit phase flight control of Galileo satellites.

Galileo control room

“At the time that the four satellites separate two by two, we’ll have two shifts of the mission team working in the control room at the CNES centre in Toulouse, France, each shift managing two satellites – so it will be an intense period,” says Liviu Stefanov, co-flight director from ESA.

“This is the same team who conducted the previous Galileo early orbit phases, so we’re familiar with the satellites themselves,” says Hélène Cottet, lead flight director from CNES.

“What’s different this time is managing four satellites, sometimes in sequence and sometimes in parallel. We have concentrated a lot of effort on planning and training for the first few hours in space.”

Since 2011, the joint team have conducted the Galileo initial flight operations alternately from ESA’s centre in Darmstadt, Germany, and the CNES centre in Toulouse.

Target orbit: 23 200 km

Cutaway view shows the four Galileo satellites mounted on top of a specially adapted Ariane 5 rocket underneath the aerodynamic fairing.

Cut-away foursome

Separation will mark the start of a set of critical activities and manoeuvres to ensure the four are ready for handover to the Galileo Control Centre in Oberpfaffenhofen, Germany for the rest of their mission.

This includes ensuring that each have opened their solar wings and are ‘power positive’, establishing a data link via a set of ground stations, conducting extensive health checks and then switching the craft into a stable Earth-pointing mode, ready for subsequent manoeuvres.

Source:European Space Agency

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