The European Space Agency’s HERA mission, fully assembled in Germany, is set to study the asteroids Dimorphos and Didymos. It will soon undergo rigorous testing in the Netherlands to ensure it is ready for space. Credit: European Space Agency/Science Office
The European Space Agency’s Hera asteroid defense mission has been successfully assembled at OHB Bremen in Germany.
Hera is complete. The European Space Agency’s Planetary Defense Asteroid mission was built and prepared in two halves, but now, through a painstaking process, they have been brought together to create a single spacecraft, ready for large-scale testing of its space readiness.
The mating took place at OHB Bremen in Germany, where the Hera base unit was lifted more than 3 meters above its thrust unit and then gradually and carefully set into place, over the course of three hours. The units were placed in cages to ensure that they were properly aligned relative to each other down to a few tenths of a millimeter.
“The mission continues to see important milestones at the moment, but this is a big mission and a very emotional moment for the team,” explains Paolo Martino, Hera System Architect. “Before we had these two modules, now you can say the spacecraft is born.”
The Hubble Space Telescope image of the asteroid Dimorphos was taken on December 19, 2022, nearly four months after the asteroid impact with NASA’s DART (Double Asteroid Reorientation Test) mission. Hubble’s sensitivity detects a few dozen rocks that fell from the asteroid with the force of the impact. The scattered boulders range in size from three feet to 22 feet, based on the Hubble Photometry. They are drifting away from the asteroid at just over half a mile per hour. Credits: NASA, ESA, David Jewett (University of California), Alyssa Pagan (STScI)
HERA is Europe’s contribution to the international planetary defense experiment. After the DART mission collided with the asteroid Dimorphos last year – modifying its orbit and sending a column of debris thousands of kilometers into space – Hera will return to Dimorphos for a close-up survey of the crater left by DART. The mission will also measure the mass and composition of Dimorphos, as well as the mass of the much larger asteroid Didymos around which Dimorphos orbits.
The HERA propulsion module includes the propellant tanks – housed within a titanium central cylinder, the spacecraft’s “workhorse” – along with tubes and thrusters, which will have the mission of ferrying the mission through deep space for more than two years, then maneuvering around Dimorphos and Didymus. This module was mated to the HERA base module at OHB Bremen to complete the spacecraft structure. Credit: Oh
In order to rendezvous with Dimorphos Hera, it must launch in October 2024. So, to maximize working time, the mission has been created by prime contractor OHB as two separate units, which can be worked on in parallel.
The HERA propulsion module includes the propellant tanks – housed within a titanium central cylinder, the spacecraft’s “workhorse” – along with tubes and thrusters, which will have the mission of ferrying the mission through deep space for more than two years, then maneuvering around Dimorphos and Didymus.
Meanwhile, the HERA core unit can be thought of as the mission’s brains, hosting the onboard computer, mission systems and instruments.
The HERA core unit can be thought of as the mission’s brains, hosting the onboard computer, mission systems and instruments. Enclosed in a cage, it can be seen here being lowered onto the spacecraft’s thrust module at OHB Bremen to complete the spacecraft. Credit: Oh
Built together, the base unit remained at OHB while the drive unit traveled to Avio near Rome, Italy to add its propulsion system. The couple was then reunited in Bremen to prepare for the mating.
“A similar dual-module process is often used for communications missions, but these are usually standardized designs,” Paolo adds. “This is the first time it has been applied to a deep space mission, on a much more customized basis.”
Hera is complete. The European Space Agency’s Planetary Defense Asteroid mission was built and prepared in two halves, but now, through a painstaking process, they have been brought together to create a single spacecraft, ready for large-scale testing of its space readiness. The mating took place at OHB Bremen in Germany, where the Hera base unit was lifted more than 3 meters above its thrust unit and then gradually and carefully set into place, over the course of three hours. The units were placed in cages to ensure that they were properly aligned relative to each other down to a few tenths of a millimeter. Credit: Oh
The mating had been comprehensively simulated beforehand using CAD software, but OHB’s assembly, integration and testing team was still checking alignment as the crane lowered the base unit every step of the way. The cleanroom door was kept closed during mating to prevent any distraction.
“We studied a lot with our designers about the most important parts of the process, so most of it has already been taken into account,” explains Matteo Grimaldi, Senior Assembly, Integration and Test Technician at OHB.
Hera and CubeSats and their rock target destination. Credit: European Space Agency/Science Office
Once the end of the drive unit cylinder meets the top surface of the base unit, mating is complete. An initial test screw was then inserted to verify that the alignment was complete before the two units were fully screwed together.
“The two modules are now together forever, as they will be in space, unless some major unforeseen problem occurs,” Paolo explains.
“If we want to, we can still access the interior modules through the side panels. After that, we will add some payload modules to the upper deck of the spacecraft that we receive directly from the manufacturers once HERA goes to its next stop.”
“It will be at the end of this month, when the Hera will be transferred to the ESTEC test center in the Netherlands, where it will undergo an extensive environmental testing campaign to verify its readiness to fly.”
Meet Hera, our asteroid investigator. Together with two CubeSats – Milani, a rock analyst, and Juventas, a radar visionary – Hera embarks on an adventure to explore Didymos, a typical double asteroid system among the thousands that pose a threat to planet Earth.
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