Galileo G2 navigation payloads begin testing

Testing on Galileo’s second-generation hardware has begun.

Test versions of the satellites’ navigation payloads is undergoing evaluation by Airbus Defence and Space at its Ottobrunn facility in Germany and by Thales Alenia Space at the ESTEC technical center in the Netherlands of the European Space Agency (ESA).

Known as the Galileo Payload Testbeds (GPLTBs), these are development models of the navigation payloads intended for the Galileo Second Generation (G2) satellites. The navigation antennas of the testbed payloads are being testing to check whether they meet the ambitious performance levels set for the G2 satellites.

Instead of being assembled from space-ready components like an actual satellite payload, the GPLTBs are built from electronic parts placed in test racks, with a proof-of-concept version of a navigation antenna attached.

“The goal with these test campaigns is to prove their design concepts early, and anticipate any technical issues that might arise as early as possible,” said Cédric Magueur, ESA’s payload manager for the Thales G2 satellites.

“These campaigns also make it possible to develop and validate new performance measurements concepts for these new generation of complex navigation payloads,” said Dirk Hannes, ESA’s payload manager for the Airbus G2 satellites. “This will allow us to optimize the production efficiency of the flight model series.”

The second satellite in the European Data Relay System (EDRS) undergoes tests at Airbus’s Compact Antenna Test Range facility. (Photo: ESA)

“Results from the testing will feed into the up-coming Preliminary Design Review for the new satellites, backing up the analyses by the companies with solid measurements,” Cédric said. “Such early testing also supports the ambitious timescale for the development and construction of G2 satellites, with the first satellites planned to reach orbit by the middle of this decade.”

There are 26 Galileo satellites now in orbit; deployment of 12 more will begin by the end of this year. Next will come the first 12 G2 satellites, featuring enhanced navigation signals and fully digital payloads. The new generation will be made up of two independent families of satellites meeting the same performance requirements, produced by Thales Alenia Space in Italy and Airbus Defence and Space in Germany.

Airbus Defence and Space’s GPLTB is undergoing radiated testing at the company’s Ottobrunn facility, inside a Compact Antenna Test Range (CATR). Meanwhile, the Thales Alenia Space GPLTB is about to start testing inside ESTEC’s own Hybrid European Radio Frequency and Antenna Test Zone (Hertz) chamber. The metal-walled chambers are isolated from external radio interference, with inner walls studded with foam pyramids to minimize radio-frequency signal reflections, mimicking the void of space.

“Up until now all GPLTB testing has taken place by plugging them into test boards,” Cédric said. “These test campaigns mark the first time that their performances will be confirmed in terms of radiating signals. In our first phase we will perform near-field measurements directly around the antenna to measure all the characteristics of the signal shape, to check it matches previous conductance tests. Then, via computation, we can derive its far-field performance.”

In the second test phase, the actual far-field measurements will be performed using another feature of the chambers, a pair of paraboloid reflectors. In this way, the signal from the testbed can be reshaped as if it had traveled the long distance that actual Galileo signals need to travel, from an altitude of 23,222 km down to Earth’s surface.

At Airbus, the testing is being undertaken in reverse order, with the far-field measurements taking place before performing the near-field measurements.