ESA’s Spacecraft for Asteroid Mission Successfully Assembled

ESA’s Spacecraft for Asteroid Mission Successfully Assembled

ESA’s 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. 

The mating took place at OHB Bremen in Germany, with Hera’s 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.

“The mission keeps on hitting milestones right now, but this is a big one, and a very emotional moment for the team,” explains Paolo Martino, Hera system engineer. “Previously we had these two modules, now you can say the spacecraft has been born.”

Hera is Europe’s contribution to an international planetary defense experiment. Following the DART mission’s impact with the Dimorphos asteroid last year – modifying its orbit and sending a plume of debris thousands of kilometers out into space – Hera will return to Dimorphos to perform a close-up survey of the crater left by DART. The mission will also measure Dimorphos’ mass and make-up, along with that of the larger Didymos asteroid that Dimorphos orbits around.

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.

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 maneuver around Dimorphos and Didymos.

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

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.

“A similar double-module process is often used for telecom missions, but those are usually standardized designs,” adds Paolo. “This is the first time it has been applied to a deep space mission, on a much more ad hoc basis.”

Complete Hera Spacecraft

The mating had been exhaustively simulated in advance using CAD software, but OHB’s 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.

“We 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,” explains Matteo Grimaldi, Senior Assembly, Integration and Testing technician at OHB.

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 two modules are now together forever, as they will be in space, barring any major unexpected problem,” explains Paolo. “If 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. “That 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.”

Click here to learn more about ESA's Hera Asteroid Mission.

Publisher: SatNow

GNSS Constellations - A list of all GNSS satellites by constellations


Satellite NameOrbit Date
BeiDou-3 G4Geostationary Orbit (GEO)17 May, 2023
BeiDou-3 G2Geostationary Orbit (GEO)09 Mar, 2020
Compass-IGSO7Inclined Geosynchronous Orbit (IGSO)09 Feb, 2020
BeiDou-3 M19Medium Earth Orbit (MEO)16 Dec, 2019
BeiDou-3 M20Medium Earth Orbit (MEO)16 Dec, 2019
BeiDou-3 M21Medium Earth Orbit (MEO)23 Nov, 2019
BeiDou-3 M22Medium Earth Orbit (MEO)23 Nov, 2019
BeiDou-3 I3Inclined Geosynchronous Orbit (IGSO)04 Nov, 2019
BeiDou-3 M23Medium Earth Orbit (MEO)22 Sep, 2019
BeiDou-3 M24Medium Earth Orbit (MEO)22 Sep, 2019


Satellite NameOrbit Date
GSAT0223MEO - Near-Circular05 Dec, 2021
GSAT0224MEO - Near-Circular05 Dec, 2021
GSAT0219MEO - Near-Circular25 Jul, 2018
GSAT0220MEO - Near-Circular25 Jul, 2018
GSAT0221MEO - Near-Circular25 Jul, 2018
GSAT0222MEO - Near-Circular25 Jul, 2018
GSAT0215MEO - Near-Circular12 Dec, 2017
GSAT0216MEO - Near-Circular12 Dec, 2017
GSAT0217MEO - Near-Circular12 Dec, 2017
GSAT0218MEO - Near-Circular12 Dec, 2017


Satellite NameOrbit Date
Kosmos 2569--07 Aug, 2023
Kosmos 2564--28 Nov, 2022
Kosmos 2559--10 Oct, 2022
Kosmos 2557--07 Jul, 2022
Kosmos 2547--25 Oct, 2020
Kosmos 2545--16 Mar, 2020
Kosmos 2544--11 Dec, 2019
Kosmos 2534--27 May, 2019
Kosmos 2529--03 Nov, 2018
Kosmos 2527--16 Jun, 2018


Satellite NameOrbit Date
Navstar 82Medium Earth Orbit19 Jan, 2023
Navstar 81Medium Earth Orbit17 Jun, 2021
Navstar 78Medium Earth Orbit22 Aug, 2019
Navstar 77Medium Earth Orbit23 Dec, 2018
Navstar 76Medium Earth Orbit05 Feb, 2016
Navstar 75Medium Earth Orbit31 Oct, 2015
Navstar 74Medium Earth Orbit15 Jul, 2015
Navstar 73Medium Earth Orbit25 Mar, 2015
Navstar 72Medium Earth Orbit29 Oct, 2014
Navstar 71Medium Earth Orbit02 Aug, 2014


Satellite NameOrbit Date
NVS-01Geostationary Orbit (GEO)29 May, 2023
IRNSS-1IInclined Geosynchronous Orbit (IGSO)12 Apr, 2018
IRNSS-1HSub Geosynchronous Transfer Orbit (Sub-GTO)31 Aug, 2017
IRNSS-1GGeostationary Orbit (GEO)28 Apr, 2016
IRNSS-1FGeostationary Orbit (GEO)10 Mar, 2016
IRNSS-1EGeosynchronous Orbit (IGSO)20 Jan, 2016
IRNSS-1DInclined Geosynchronous Orbit (IGSO)28 Mar, 2015
IRNSS-1CGeostationary Orbit (GEO)16 Oct, 2014
IRNSS-1BInclined Geosynchronous Orbit (IGSO)04 Apr, 2014
IRNSS-1AInclined Geosynchronous Orbit (IGSO)01 Jul, 2013