On 25 July, four new satellites for the European Galileo satellite navigation constellation were placed into orbit by Ariane 5. Over the last 12 days, CNES’s experts have completed a demanding and vital sequence of operations to position the satellites on orbit with extreme precision and ready them for operational service.
Operations were conducted from the Toulouse Space Centre (CST) where, after monitoring the deployment of the satellites’ solar arrays, teams determined their orbits and updated manoeuvring strategies. The teams also spun up and checked the attitude control reaction wheels over a period of roughly 24 hours during which the satellites remained pointed at the Sun, before switching them in sequence into nominal Earth-pointing mode as planned. They then performed three scheduled manoeuvres to put each satellite in a drift orbit to separate them and take them to their final positions. Today marked the end of these manoeuvres as control of the four satellites was handed over to the Galileo Control Centre in Oberpfaffenhofen, Germany. From 23 September through to end October, the second part of the Launch and Early Orbit Phase (LEOP) will see CNES’s experts bring the satellites out of their drift orbit and finely tune their positions to within five metres of their intended orbital slots.
These four satellites positioned by CNES bring the current Galileo constellation to 26 satellites, thus concluding an accelerated deployment cycle since 2015, going from 6 satellites to 26 in three years, notably thanks to Ariane 5’s ability to launch four satellites at a time.
Galileo has been delivering an operational service to several hundred million users since December 2016. Service availability is being constantly improved as the number of satellites in the constellation approaches the ultimate goal of 30. Only 24 satellites are required to provide positioning accurate to one metre anywhere in the world, anytime. The six additional satellites will provide back-up in the event of anomalies and during maintenance operations, and will replace satellites reaching the end of their design life in order to assure continuity of service for Galileo’s hundreds of millions of users.