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ESA\u2019s asteroid mission for planetary defense 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. <\/p>\n
The mating took place at OHB Bremen in Germany, with Hera\u2019s Core Module raised more than 3 m above its Propulsion Module and 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 millimeter.<\/p>\n
\u201cThe mission keeps on hitting milestones right now, but this is a big one, and a very emotional moment for the team,\u201d explains Paolo Martino, Hera system engineer. \u201cPreviously we had these two modules, now you can say the spacecraft has been born.\u201d<\/p>\n
Hera is Europe\u2019s contribution to an international planetary defense experiment. Following the DART mission\u2019s impact with the Dimorphos asteroid last year \u2013 modifying its orbit and sending a plume of debris thousands of kilometers out into space \u2013 Hera will return to Dimorphos to perform a close-up survey of the crater left by DART. The mission will also measure Dimorphos\u2019 mass and make-up, along with that of the larger Didymos asteroid that Dimorphos orbits around.<\/p>\n
To make its rendezvous with Dimorphos Hera has to lift off in October 2024. So to maximize working time the mission was constructed by prime contractor OHB as two separate modules, which could be worked on in parallel.<\/p>\n
Hera\u2019s Propulsion Module incorporates its propellant tanks \u2013 housed within a central titanium cylinder, the \u2018backbone\u2019 of the spacecraft \u2013 along with piping and thrusters, which will have the job of hauling the mission across deep space for more than two years, then to maneuver around Dimorphos and Didymos.<\/p>\n
Meanwhile, Hera\u2019s Core Module can be thought of as the brains of the mission, hosting its onboard computer, mission systems, and instruments.<\/p>\n
Manufactured together, the Core Module remained at OHB while the Propulsion Module traveled to Avio near Rome in Italy for the addition of its propulsion system. The pair were then reunited in Bremen to prepare for the mating operation.<\/p>\n
\u201cA similar double-module process is often used for telecom missions, but those are usually standardized designs,\u201d adds Paolo. \u201cThis is the first time it has been applied to a deep space mission, on a much more ad hoc basis.\u201d<\/p>\n
The mating had been exhaustively simulated in advance using CAD software, but OHB\u2019s assembly, integration, and testing team were still checking alignment as the crane lowered the Core Module every step of the way. The cleanroom door was kept sealed during the mating to prevent any distractions.<\/p>\n \u201cWe studied a lot together with our designers on which were the most critical parts of the process, so most of them were already taken into account,\u201d explains Matteo Grimaldi, Senior Assembly, Integration and Testing technician at OHB.<\/p>\n 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.<\/p>\n \u201cThe two modules are now together forever, as they will be in space, barring any major unexpected problem,\u201d explains Paolo. \u201cIf we need to, we can still access internal units through side panels. Next, we will be adding some payload units to the spacecraft’s top deck which we are receiving directly from the manufacturers once Hera moves to its next stop. \u201cThat is at the end of this month when Hera is being transported to the ESTEC Test Centre in the Netherlands, where it will go through a full-scale environmental test campaign to check its flight readiness.\u201d<\/p>\n![](\"https:\/\/cdn.satnow.com\/news\/hera_3_638285372492327962.jpg\")
Complete Hera Spacecraft<\/span><\/span><\/span><\/p>\n