Hera is complete. ESA’s asteroid mission for planetary defence was built and prepared in two halves, but now, through a painstaking operation, they have been mated together to make a single spacecraft, ready for full-scale testing of its readiness for space.

The mating took place at OHB Bremen in Germany, with Hera’s Core Module raised more than 3 m above its Propulsion Module then gradually and carefully slotted into place, over a three-hour period. The modules had been placed in cages to ensure their correct alignment relative to each other down to a few tenths of a millimetre.

Hera’s Propulsion Module incorporates its propellant tanks – housed within a central titanium cylinder, the ‘backbone’ of the spacecraft – along with piping and thrusters, which will have the job of hauling the mission across deep space for more than two years, then to manoeuvre around the Dimorphos and Didymos asteroids.

Meanwhile Hera’s Core Module can be thought of as the brains of the mission, hosting its onboard computer, mission systems and instruments.

Once the tip of the Propulsion Module cylinder met the top deck of the Core Module the mating was complete. Then an initial test bolt was inserted to check the alignment was entirely correct in advance of the two modules being fully bolted together.

The combined Hera spacecraft is scheduled to go through a test campaign to assess its readiness for spaceflight, along with the two CubeSats it will carry aboard, in preparation for its October 2024 lift-off.

Access the related broadcast quality footage.