The European Space Agency’s (ESA) Planetary Transits and Oscillations of Stars (Plato) mission is gearing up to explore one of science’s biggest questions: are there other Earth-like planets out there?

Set to launch in 2026, Plato will head to a special region in space about 1.5 million kilometres from Earth. From this cosmic vantage point, it will hunt for distant worlds orbiting Sun-like stars – particularly those in the ‘habitable zone,’ where conditions could be just right for liquid water, and maybe even life.

But before Plato can begin its planet-hunting adventure, ESA needs to make absolutely sure the spacecraft can ‘talk’ to Earth once it's out there. That’s where the Ground Segment Reference Facility (GSRF) comes in. Tucked inside ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, the GSRF is a high-tech rehearsal space. It allows engineers to test every aspect of a mission’s ground segment – the complex web of antennas, hardware, software, and networks that will keep Plato connected to ESA mission control.

The radio frequency tests that took place in April 2025 made sure that Plato’s communication system is capable of exchanging information and otherwise interacting smoothly with the 35-metre deep space antennas in ESA’s Estrack network.

To conduct the tests, engineers placed a physical replica of Plato’s communication hardware inside a shielded Faraday cage, which blocks out all external electromagnetic interference. This allowed them to isolate Plato’s signals and verify its communication system in a clean, controlled environment and to catch potential glitches long before Plato blasts off.

The hardware replica will remain at ESOC throughout Plato’s mission, where it will live alongside similar equipment belonging to ESA’s other science missions, such as Euclid, BepiColombo and Juice. Having this equipment on hand at all times helps ESA teams troubleshoot and solve any unexpected communication issues encountered while the spacecraft is in space.

Similar tests take place at the GSRF to ensure that ESA’s antennas are compatible with partner missions supported by the Agency, such as JAXA’s Martian Moons Exploration mission and ISRO’s Gaganyaan human spaceflight capsule.

This image shows the signal flowing from Plato’s radio, out of the Faraday cage through a cable, and into the nearby rack of engineering equipment that is accurately mimicking one of ESA’s deep space antennas. In the future, a signal that looks very similar to this may arrive at a real ground station carrying exciting information about newly discovered distant worlds.