The foam pyramids around Hera absorb radio signals, while the Maxwell chamber's 9-m high metal walls block external radio interference. This space mimics the void of space, allowing the Hera team to validate the spacecraft's interaction with its CubeSats through its Low Gain Antenna, while maintaining contact with Earth through its High Gain Antenna.

"We're testing that Hera can communicate with its CubeSats while also talking to Earth, without unexpected interference," explains Hera systems engineer Franco Perez Lissi. "Accordingly Hera's mission control team at ESA's European Space Operations Centre, ESOC, in Darmstadt, Germany, is also talking directly with the spacecraft for the first time, through the High Gain Antenna, just as they will when the mission is in space."

Hera, ESA's first planetary defense mission, is set for launch in October. It will travel to the Didymos binary asteroid system to survey the Dimorphos moonlet. Dimorphos is the first Solar System object to have its orbit changed by human activity, following NASA's DART mission impact in 2022.

Hera aims to collect critical data about Dimorphos, turning DART's experiment into a well-understood planetary defense technique. Hera carries ESA's first deep space CubeSats, equipped with instruments to gather data closer to the asteroid's surface and eventually land.

The Juventas CubeSat has a radar instrument to probe the asteroid's internal structure and a gravity-detecting gravimeter. The Milani CubeSat hosts a multispectral imager to survey surface mineralogy and a dust surveyor.

Inter-satellite links between the CubeSats and Hera will enhance the accuracy of Hera's measurements of Dimorphos's mass by analyzing gravity-driven Doppler shifts.

"Our testing of how Hera works with its CubeSats starts with the initial deployment process, which occurs differently from that of any standard CubeSat," adds Franco. "The Deep Space Deployer on Hera's topside 'Asteroid Deck' part releases each CubeSat, so it emerges from the spacecraft but still has power and data tethers connecting it. This will allow us to check the CubeSat is fully operational, and its radio link with Hera works as needed, before each one is fully deployed into space around a day later, to begin its own mission."

After the initial phase, testing will simulate the communications of the CubeSats in free flight back with Hera.

Related Links
Hera at ESA
Asteroid and Comet Mission News, Science and Technology