Galileo L-band antenna at Redu

Redu trains big dish on Galileo satellites

22/11/2011 1522 views 1 likes
ESA / Applications / Navigation

Launched in October, Europe’s first two Galileo navigation satellites orbit Earth about every 14 hours. As they transmit over Europe, ESA’s Redu centre in Belgium is ready to receive and analyse their signals.

Nestled deep within Belgium’s Ardennes forest, Redu is assessing the quality of the navigation signals transmitted by Galileo. The rigorous In-Orbit Test campaign began this month and will take around 90 days.

Galileo will offer a total of five different navigation services – transmitting on three different frequencies for added accuracy. Results gathered by this campaign will set a benchmark throughout the satellites’ 12-year operational lives and act a reference for the rest of the Galileo constellation set to follow the first two satellites into space.

ESA's Redu centre
ESA's Redu centre

“The platform side of both satellites underwent activation from Toulouse during the Launch and Early Operations Phase in the two weeks following launch, followed by hand-over to the Galileo Control Centre in Oberpfaffenhofen near Munich for platform commissioning and fine positioning manoeuvres” explained Marco Falcone, Galileo System and Validation Manager.

“Now we are at the stage of checking the Galileo payloads were not affected by launch and are working according to specifications.”

First two Galileo IOV satellites
First two Galileo IOV satellites

Opened in 1968, Redu was selected for the campaign because of its long heritage performing similar assignments for European telecommunications satellites.

For Galileo, the Redu centre has been equipped with a 20 m-diameter L-band antenna to receive navigation signals and a C-band transmit antenna to test the onboard mission receiver and be able to uplink navigation messages to the satellite.

A UHF antenna is also available for transmitting simulated search and rescue signals to the satellites.

Galileo's 20-m L-band antenna
Galileo's 20-m L-band antenna

“Because the satellites are so far away in space – up at 23 222 km altitude – we require a very large dish to pick up the signals with all the fine detail necessary,” added Marco.

“With this 20 m high-gain antenna we can capture the exact shape of the spread spectrum signals being transmitted, and can compare them to what we expected.”

As the tests are performed, Redu is in constant communication with the Galileo Control Centre, from where the satellite platforms are being controlled.

UHF antenna
UHF antenna

Once the campaign is completed then oversight of the Galileo payloads will pass to Galileo’s second control centre, at Fucino in central Italy.

The campaign mirrors a similar set of end-to-end tests carried out by Galileo’s team at the start of the year, except then the satellites were sitting in their integration facility at Thales Alenia Space in Rome.

“It helps ensure that ESA will be handing over to the European Commission a fully operational system, matching all the original requirements,” notes Marco.

Redu, extended and fitted to fulfil its mission, will be kept ready to check all future Galileo satellites, starting with the second pair in 2012.

“Redu serves ESA missions including the Artemis data relay satellite, the Earth-observing Proba-1 and Sun-watching Proba-2, and is the site of ESA’s new space weather data centre for Space Situational Awareness,” says Daniele Galardini, who heads the centre.

“Today, Galileo represents a new exciting mission that will fully exploit the expertise acquired in Redu during its life and the investments of the past five years.”

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