News from the European Space Agency (ESA)
Within ESA’s Maxwell EMC Facility, each Galileo satellite is switched on as if it were already operating in space. The test procedure is a check of the satellite’s electromagnetic compatibility; all its systems are run together to detect any harmful interference between them.
Once Maxwell’s main door is sealed, its metal walls form a Faraday Cage, screening out external electromagnetic signals. The anechoic foam pyramids covering its interior absorb internal signals – as well as sound – to prevent any reflection, mimicking the infinite void of space for satellite testing.
In the photo here, sheathed in multi-layer insulation, the 2.5 x 1.2 x 1.1-meter satellite’s main 1.4-m diameter antenna transmits L-band navigation signals. To its left is the hexagonal search and rescue antenna that will pick up distress signals and relay them to local emergency services, contributing to saving more than 2,000 lives annually.
The Face of Galileo: A Galileo satellite is tested in the Maxwell EMC Facility before heading for space. (Photo: ESA)
To the bottom right of the navigation antenna are a pair of infrared Earth sensors to keep the navigation permanently locked onto Earth by homing in on the contrast between the heat of Earth’s atmosphere and the cold of deep space.
Above them is the laser retro-reflector: lasers are shone up to this from International Laser Ranging Service stations to perform an independent check of the satellite’s orbital position down to an accuracy of less than a centimeter, as a backup of standard radio ranging.
Above that is the circular C-band antenna, which every 45 minutes or so receives the navigation messages from the Galileo ground segment. These signals incorporate corrections for slight clock errors, orbital drift or satellite malfunctions that user receivers can process as they perform positioning fixes, helping ensure Galileo delivers meter-scale positioning to users around the globe.
What resembles a white baton on the end of the satellite is its S-band antenna, employed to return “housekeeping” telemetry data to mission control on Earth and pick up telecommands to operate the satellite platform and payload – as well as performing the ranging used to estimate the satellite’s position in space.
The Maxwell EMC Facility is part of the ESTEC Test Centre in ESA’s technical heart in Noordwijk, the Netherlands – Europe’s largest satellite testing facility, which has flight-tested all but two of the 28 Galileo satellites already in orbit, and is doing the same for the next 10 satellites planned to join the constellation.