CubeSats are small satellites typically used for educational purposes or minor tasks in Earth’s orbit. However, in this case, the Milani Cubesat, together with Juventas, will be the first ESA CubeSats to travel into space for months, with the Hera mission to rendezvous with a binary asteroid system in 2026.
“This is a paramount achievement for Tyvak International. Milani is now ready to be delivered to ESA and undergo the system tests with Hera, to ensure the validation of the interfaces and the end-to-end communication prior to the launch.”
— Margherita Cardi, VP Programmes for Tyvak International and Milani Programme Manager
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Milani CubeSat instruments
The Milani CubeSat is named after Giovanni Domenico Milani, an Italian astronomer known for his contributions to asteroid orbit studies and celestial dynamics research.
He was also the first to devise what became ESA’s Near Earth Object Coordination Centre, based at the Agency’s ESRIN center in Frascati, Italy. The name pays tribute to his significant impact in the field of astronomy, reflecting the satellite’s mission to study the Didymos asteroid.
Developed by Tyvak International srl, the CubeSat is dedicated to the visual inspection and detection of dust on the Didymos asteroid after the DART impact. Its primary scientific objectives are to map the global composition of the Didymos asteroids, characterize their surface, evaluate the effects of NASA’s DART mission, and study dust clouds surrounding the asteroid.
The Milani CubeSat is equipped with advanced instruments tailored to its mission. VISTA is a micro-thermogravimeter that efficiently detects dust particles and volatiles. ASPECT is a miniaturized hyperspectral imager that captures 2D snapshots from visible to SWIR wavelengths, forming spectral datacubes. ASPECT has four independent measurement channels, including VIS, NIR, and SWIR, with tunable FPIs.
Other onboard tools include accelerometers and gyros for landing dynamics, a visible camera, and star trackers for attitude monitoring. Additionally, an Inter-Satellite Link (ISL) enables radio science, allowing gravity field measurements beyond the capabilities of Hera alone.
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Hera mission and the Role Of Milani CubeSat
The Hera mission is a planetary defense initiative aimed at studying ways to alter the orbit of asteroids to protect Earth when necessary. Didymos, which is orbited by a smaller asteroid called Dimorphos, does not currently pose a threat to Earth. However, conducting experiments on these asteroids will be useful in ensuring Earth’s safety in the future.
On September 26, 2022, NASA’s DART Mission impacted Dimorphos in an attempt to reduce the orbital period of the asteroid around Didymos by 10 minutes. In October 2022, NASA declared that the mission was a success because the reduction was of 32 minutes.
The upcoming Hera mission will revisit this small pair of asteroids to study the crater left by DART, the composition of Dimorphos, its surface temperature, and its internal structure.
Meanwhile, Hera will deploy two CubeSats, Juventas and Milani, to collect even more detailed data before attempting to land.
Together, the data from ESA’s Hera mission and NASA’s DART mission will help us understand how this technique might be used in the future to deflect an asteroid in a collision orbit with Earth.
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A long trip and a tricky deployment
Milani and Juventas will spend two years traveling to Dymiphos aboard the Hera probe. The launch is scheduled for October 2024, and the Hera rendezvous is planned for December 2026.
To maintain the health of the nanosatellites during Hera’s two-year deep-space cruise and ensure their proper functioning before releasing them within the asteroid’s ultra-low gravitational field, the mothership is equipped with Deep Space Deployers (DSDs). The DSDs are positioned at opposite ends of Hera’s upper side. Unlike standard deployers used for CubeSat missions in low Earth orbit, which support the satellites during their turbulent journey to space and then inject them into orbit with a quick release, Hera’s DSDs must operate for a longer period and release their cargo gradually due to the asteroid’s minimal gravity. This slower release prevents the CubeSats from missing the asteroid.
“In addition, the two DSD will be used to communicate with their CubeSats, throughout Hera’s approximately two-year voyage to Dimorphos, exchange telemetry and telecommands, update software, charge batteries, test reaction wheels and perform final health checks.”
— Franco Perez Lissi, Hera’s ESA system engineer
When they are ready to deploy, the deployment does not happen simultaneously. Initially, the CubeSat is pushed to the top of the DSD by springs, but it remains connected to Hera through an umbilical for power and communications. Over approximately 24 hours, each CubeSat undergoes system activation and checks while being exposed to space. This includes testing the inter-satellite links for communication with Hera. Finally, they are released slowly and precisely.
Overall, the Milani CubeSat, in conjunction with the Hera probe, will significantly enhance our capacity to alter the orbit of asteroids, safeguarding our planet from these rare yet dangerous events in the future.
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