CubeSats Mark Milestone in ESA’s Hera Planetary Defense Mission

The recent activation of the two CubeSats aboard ESA’s Hera mission has marked a significant milestone in planetary defense efforts. With their first signals sent back to Earth, both Juventas and Milani have confirmed their operational readiness, showcasing the capabilities of these miniature spacecraft designed to gather crucial data on asteroids.

Launched on 7 October, Hera is ESA’s inaugural mission focused on planetary defense, specifically targeting Dimorphos, the asteroid whose orbit was altered by NASA’s DART mission in 2022. This endeavor doesn’t just focus on the main spacecraft; it also involves two shoebox-sized CubeSats that will venture closer to the asteroid to collect additional scientific data.

“Each CubeSat was activated for about an hour in turn during live sessions with the ground to perform commissioning tests,” explains Franco Perez Lissi, the Hera CubeSats Engineer. This rigorous check involved activating and testing various onboard systems, including platform avionics and inter-satellite communication links. The CubeSats’ reaction wheels, necessary for maintaining attitude control, were also tested to confirm their functionality.

Juventas and Milani were designed to complement each other’s missions. Juventas, developed by GOMspace, will conduct the first-ever radar probing of an asteroid, providing insights into the internal structure of Dimorphos. In contrast, Milani, crafted by Tyvak International, is set to perform multispectral mineral prospecting, which will reveal valuable information about the composition of the asteroid’s surface.

The commissioning took place at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, and was closely coordinated with the European Space Security and Education Centre (ESEC) in Belgium. This complex setup especially important for ensuring that communication and data transfer between the various teams and control centers operate smoothly throughout the mission.

As the CubeSats were activated, the distances involved presented unique challenges. Juventas was activated when it was approximately 4 million kilometers away from Earth, while Milani was turned on at a staggering distance of 7.9 million kilometers. The vast stretches of space result in significant communication delays: a 32.6-second round trip for Juventas and a 52-second round trip for Milani, leading to an exhilarating yet tense wait for the teams back on Earth.

“This commissioning has not only confirmed the CubeSat instruments and systems work as planned but has also validated the entire ground command infrastructure,” remarked Sylvain Lodiot, Hera Operations Manager. The setup involves a sophisticated network where data is managed and relayed among multiple centers, ensuring that telemetry is accurately received and processed in real-time.

The CubeSats demonstrated remarkable resilience during their initial tests, as noted by Andrea Zanotti, Milani’s Lead Software Engineer: “Milani didn’t experience any computer resets or out-of-limits currents or voltages, despite its deep space environment.” Camiel Plevier, lead software engineer for Juventas, also reported similarly favorable results, highlighting that both CubeSats maintained healthy battery levels even in the cold conditions of space.

Once Hera reaches Dimorphos towards the end of 2026, the CubeSats will be deployed gently at a speed of just a few centimeters per second. This meticulous approach is vital due to Dimorphos’s low gravitational pull, which could easily lead to a loss of the CubeSats if they were to be released too quickly.

Franco notes the significance of the successful commissioning phase: “This is a significant achievement for ESA and our industrial partners, demonstrating that a spacecraft can effectively operate alongside smaller companion spacecraft.” The future of space exploration promises to be thrilling as ESA plans additional missions like Ramses for planetary defense and the Comet Interceptor spacecraft, which will further expand our understanding of celestial bodies.

The CubeSats will be reactivated every two months throughout Hera’s cruise phase, allowing for ongoing maintenance and updates to ensure they remain in optimal condition. This routine is essential for preparing them for the groundbreaking scientific tasks that lie ahead as they approach their target and embark on an unprecedented journey into the unknown realms of our Solar System.