#^Hera observes asteroids as DART reveals more about its destination
Travelling through the asteroid belt, the European Space Agency’s Hera spacecraft has taken its first images of asteroids. The spacecraft is heading toward asteroid 65803 Didymos and its companion Dimorphos, on a mission to study the results of an intentional collision between NASA’s DART spacecraft and Dimorphos. The new images validate Hera’s capabilities to lock its cameras onto a faint target to guide itself towards its destination.
The Double Asteroid Redirection Test (DART) crashed into Dimorphos on Sept 26, 2022, intending to change the asteroid’s course. Telescopes on Earth imaged the impact alongside space-based observatories such as Hubble and the James Webb Space Telescope. Additionally, DART deployed a companion, the Light Italian Cubesat for Imaging of Asteroids (LICIACube), ahead of its collision, which imaged the debris from up close.
A recent study analyzed the debris with LICIACube’s images and found boulders ejected at high speed. Analyzing how this expelled material could have changed Dimorphos’ trajectory, the team found that DART likely changed the tilt, or inclination, of its orbit around Didymos. Hera will be able to measure and confirm these effects after it arrives at the binary asteroid.
Together, DART and Hera lay the foundations for future planetary protection missions. Focusing on asteroids that could pose harm to our planet, these missions require planning and execution at short notice, sending a spacecraft to rendezvous with the asteroid and study or even deflect it.
https://www.nasaspaceflight.com/wp-content/uploads/2025/08/liciacube_video.mp4(Video: LICIACube captured the immediate aftermath of DART’s impact as it passed by Dimorphos minutes after. Credit: Farnham et al.)DART’s impact successfully altered Dimorphos’ path around Didymos, shortening its orbit by about 33 minutes. LICIACube separated from the main DART spacecraft 15 days ahead of the impact. It flew past Didymos a few minutes after the event and recorded the debris from multiple perspectives as it flew by.
Astronomers analyzed LICIACube’s images and modelled the plume of debris to gain better insight into DART’s collision, but did not provide much detail about the composition of the debris. The new study aimed to fill in these gaps by leveraging LICIACube’s changing perspective to locate and track individual boulders in the debris field.
“We saw that the boulders weren’t scattered randomly in space,” said lead author Tony Farnham of the University of Maryland (UMD). “Instead, they were clustered in two pretty distinct groups, with an absence of material elsewhere, which means that something unknown is at work here.”
https://www.nasaspaceflight.com/wp-content/uploads/2025/08/liciacube_boulders_video.mp4(Video: Boulders identified in LICIACube’s images. The highlighted South Cluster is believed to originate from a rock named Atabaque. Credit: Farnham et al.)The team reprocessed to remove noise and enhance the visibility of individual pieces of debris. They identified 104 boulders ranging from 20 cm to 3.6 m in diameter, hurtling away from the asteroid at speeds up to 52 m/s. Many of these boulders were found outside the main dust plume, indicating that they might have originated from collisions with different parts of the spacecraft.
The scientists believe that one particular group, containing about 70% of the tracked objects, may have ejected after DART’s solar panels slammed into it, which impacted moments earlier than the main spacecraft bus.
“DART’s solar panels likely hit two big boulders, called Atabaque and Bodhran, on the asteroid,” said co-author Jessica Sunshine of UMD. “Evidence suggests that the southern cluster of ejected material is probably made up of fragments from Atabaque, a 3.3-meter-radius boulder.”
The boulders and dust forming visible in LICIACube’s images were ejected sideways, imparting a perpendicular force on Dimorphos, which likely changed the asteroid’s orbital inclination. While this effect is too subtle for telescopes on or near Earth to measure, Hera should be able to easily observe the slight change in tilt. Eventually, tidal forces will pull the asteroid’s orbit back to its original inclination, but this happens slowly enough not to meaningfully affect the orbit before Hera’s arrival.
“Data gathered from LICIACube provides additional perspectives on impact events, especially as DART was originally designed to solely rely on Earth-based observations,” said Farnham. “Hera will do the same by giving us another direct view of the impact’s aftermath, relying on the predictions we’ve made using data gathered from DART.”
(Video: Asteroid 1126 Otero captured by Hera on May 11. Credit: ESA)On Oct. 7, 2024, a SpaceX Falcon 9 lifted off from Cape Canaveral, lofting Hera into space. The spacecraft flew by Mars on March 12 and is now travelling through the asteroid belt, observing faint asteroids to test its instruments. Over the next year, Hera will slowly catch up with Didymos and Dimorphos, where it will arrive in December 2026.
Hera pointed its Asteroid Framing Camera (AFC) at asteroid 1126 Otero on May 11, observing the asteroid for three hours and taking images every six minutes. The AFC serves dual purposes as a science instrument and a navigation instrument. By observing Otero, it demonstrated the latter, which it needs to guide Hera on its approach to the binary Asteroid.
“Didymos will also be a tiny, faint point of light among the stars when it first appears,” said ESA Flight Dynamics Engineer Giacomo Moresco, of ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany. “The spacecraft will need to identify Didymos as soon as possible and keep the asteroid in the centre of the camera’s field of view as it approaches.”
In addition to the AFC’s two redundant monochrome cameras sensitive to visible light, Hera is fitted with a suite of instruments. The Thermal Infrared Imager (TIRI) provided by the Japan Aerospace Exploration Agency (JAXA) will map the temperature of the asteroid’s surface, while the Dutch HyperScout H spectrometer will picture the asteroid in 25 visible and infrared colors. Additionally, the spacecraft is fitted with star trackers, a laser range finder, communications instruments, and a camera to monitor its two companion CubeSats.
Illustration of Hera deploying its two CubeSats, Milani and Juventas. (Credit: ESA/Science Office)
On its final approach to Didymos and Dimorphos, Hera will deploy a pair of CubeSats that will help study the asteroids in more detail. The first, called Milani, will study the dust surrounding Dimorphos and take spectral images of both asteroids to study their compositions. The other spacecraft, named Juventas, will line up with Hera to perform radio science experiments and study Dimorphos’s interior using radar. After their respective observations, both CubeSats will attempt a soft landing on Dimorphos.
“The Hera spacecraft is performing very well,” notes Moresco. “So, we can use the cruise phase to test procedures and carry out other activities that will help us prepare for arrival, such as attempting to observe nearby asteroids.”
When Hera gets its first glimpse of the binary asteroid, it will be over six times dimmer than Otero. To prove it would be able to spot the pair, Hera observed another asteroid named 18805 Kellyday on July 19.
“Kellyday appeared roughly 40 times fainter than Otero,” said Moresco. “So, these observations really pushed the limits of Hera’s faint object detection and of our image processing capabilities. But nonetheless, we spotted it!”
Asteroid 18805 Kellyday captured by Hera on July 19. (Credit: ESA)
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Observing Otero and Kellyday not only verified Hera’s instruments but also demonstrated ESA’s capabilities of observing new astronomical objects. After vetting hundreds of thousands of asteroids for their suitability as an observation target, Hera’s Flight Dynamics and Flight Control teams planned and executed the observations in only a couple of weeks.
“By demonstrating that we can safely and efficiently command Hera to observe a new target on short notice, we are building confidence for the mission’s science phase, while also demonstrating a potential framework for rapid-response observations of interesting objects in deep space,” said Moresco.
ESA envisions that these capabilities could be used to study newly discovered astronomical objects. The agency might use the process to study newly discovered asteroids such as 2024 YR4, which, for a short period, was believed to be on a potential collision course with the Earth in 2032. More observations ultimately eliminated this possibility, but the rapid-response operations demonstrated by Hera might accelerate this process for future studies.
Besides its demonstrated agility when observing asteroids, Hera might also accelerate ESA’s future asteroid missions. Hera’s architecture serves as a base for the agency’s forthcoming Ramses mission to the asteroid 99942 Apophis, which will approach Earth within 32,000 km on April 13, 2029.
Illustration of ESA’s Ramses mission to asteroid 99942 Apophis. (Credit: ESA/Science Office)
Although this encounter provides a unique opportunity for performing science and testing planetary defense capabilities, the mission must be executed on a tight schedule to meet the required launch date in 2028. By building on Hera, ESA hopes to leapfrog the development process.
“The Ramses mission concept reuses much of the technology, expertise, and industrial and science communities developed for the Hera mission. Hera demonstrated how ESA and European industry can meet strict deadlines, and Ramses will follow its example,” said Ramses Project Manager Paolo Martino of ESA when the mission was announced in July 2024.
In addition to its Hera-derived main spacecraft, the Ramses mission also carries two CubeSats. One combines the observational capabilities of Milani and Juventas, featuring both a dust analyzer and a low-frequency radar. The other spacecraft will be deployed a few kilometers from Apophis and study the asteroid before landing on its surface.
Although ESA and its partners are already working on Ramses, the mission still awaits formal approval from ESA’s Ministerial Council, which is set to decide on the mission’s funding in November.
Animation of asteroid 99942 Apophis’ encounter with Earth on April 13, 2029. (Credit: ESA)
Missions like DART, Hera, and Ramses will help astronomers better understand asteroids and the threat they might pose to our planet and its inhabitants. Moreover, these missions prepare space agencies and the space industry to quickly respond to these threats. All findings from these missions, including the tiny changes to Dimorphis’ orbital inclination suggested by LICIACube’s images, add to the body of knowledge that might eventually save our planet from disaster.
“If an asteroid was tumbling toward us, and we knew we had to move it a specific amount to prevent it from hitting Earth, then all these subtleties become very, very important,” explained Sunshine. “You can think of it as a cosmic pool game. We might miss the pocket if we don’t consider all the variables.”
Farnham et al.’s study was published in the journal The Planetary Science Journal on July 4.(Lead image: Illustration of Hera and its CubeSats at the binary asteroid pair Didymos and Dimorphos. Credit: ESA/Science Office)
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