The pair were launched from Europe’s Spaceport in French Guiana on May 24 (http://galileognss.eu/galileo-liftoff-replay-soyuz-vs15/).
After launch and maneuvers to reach their final orbital altitude, their navigation and search-and-rescue payloads were methodically switched on and checked out. Their performance was assessed in relation to the rest of Galileo system.
This lengthy test phase saw the satellites being run from the second Galileo Control Centre in Oberpfaffenhofen, Germany, while their payloads’ output was assessed from the European Space Agency’s (ESA’s) Redu centre in Belgium, equipped for the tests with specialized antennas for receiving and uplinking signals.
The test campaign measured the accuracy and stability of the satellites’ atomic clocks — essential for the timing precision to within a billionth of a second as the basis of satellite navigation — as well as assessing the quality of the navigation signals.
Oberpfaffenhofen and Redu were linked for the entire campaign, allowing the team to compare Galileo signals with satellite telemetry in near-real time, according to ESA.
These two satellites were visible in the sky above Redu for a limited time each day, ranging from three to nine hours, so tests were scheduled accordingly.
Now that in-orbit testing is completed, the satellites are transmitting working navigation signals and are ready to relay any Cospas–Sarsat distress calls to emergency services.
The next four satellites, launched together on Nov. 17 (http://galileognss.eu/launch-of-4-new-galileo-satellites/), are beginning the same in-orbit testing activity, with the aim of joining the network next spring.