The European Space Agency (ESA) has let a €129.4 million contract covering detailed design, development, manufacturing and testing of HERA, the agency’s first planetary defence mission, it announced on 15 September. This constitutes Europe’s contribution to an international asteroid deflection effort, which will conduct sustained exploration of a double asteroid system.
Named after the Greek goddess of marriage, HERA will operate in conjunction with NASA’s Double Asteroid Redirect Test (DART) spacecraft in providing Earth’s first probe to rendezvous with a binary asteroid system, a little understood class making up around 15% of all known asteroids.
The contract was signed by ESA and OHB System AG of Bremen, prime contractor for the HERA consortium, at the agency’s ESOC centre in Darmstadt, which will serve as mission control for the 2024 HERA mission.
Both spacecraft fall under the joint Europe/US Asteroid Impact & Deflection Assessment (AIDA) programme. The DART spacecraft – due for launch in July 2021 – will first conduct a kinetic impact on the smaller of the two bodies. The desk-sized HERA will then follow up with a detailed post-impact survey to turn the experiment into a well-understood, repeatable asteroid deflection technique.
While doing so, HERA will also demonstrate multiple novel technologies, such as autonomous navigation around the asteroid – like modern driverless cars on Earth – while gathering crucial scientific data, to help scientists and future mission planners better understand asteroid compositions and structures. It will also deploy Europe’s first CubeSats (already under contract and in development) into deep space for close-up asteroid surveying, including the very first radar probe of an asteroid’s interior – using an updated version of the radar system carried on ESA’s ROSETTA comet mission.
Due to launch in October 2024, HERA will travel to a binary asteroid system – the Didymos pair of near-Earth asteroids, comprising a 780 m-diameter mountain-sized main body, orbited by a 160 m moon, christened Dimorphos in June, about the size of the Great Pyramid of Giza.
DART’s kinetic impact into Dimorphos in September 2022 is expected to alter its orbit around Didymos, as well as create a substantial crater. This moonlet asteroid will become unique, as the first celestial body to have its orbital and physical characteristics intentionally altered by human intervention. HERA will arrive at the Didymos system at the end of 2026, to perform at least six months of close-up study.
Of 17 ESA member states contributing to HERA, Germany is at the forefront, tasked with overall spacecraft design and integration, main navigation cameras, tanks, thrusters, high-gain antenna, reaction wheels, and mass memory unit.
Italy is leading the mission’s power and propulsion subsystems, and is providing the deep-space transponder that will enable the mission’s radioscience experiment. It is also leading the dust and mineral prospecting CubeSat, named after the late asteroid scientist Andrea Milani.
Belgium is developing HERA’s on-board computer and software, the brain of the spacecraft, plus its power conditioning and distribution unit - the heart of its electrical subsystem. It is also contributing to the Japanese-developed thermal imager and CubeSats operations centre.
Luxembourg is leading the radar-hosting JUVENTAS CubeSat and the inter-satellite communication system allowing the two HERA CubeSats to communicate with Earth through an innovative network using HERA as data relay.
Portugal and Romania are developing the laser altimeter, which will provide crucial information for the autonomous navigation functions. In addition, Romania is developing the image processing unit, harness and the electrical test equipment, while also contributing to its GNC development.
The Czech Republic is responsible for the full satellite structure, payload software (to command the instruments), independent software validation and ground support equipment for pre-flight satellite testing. It is also providing components for JUVENTAS’ low-frequency radar and data processing software on the second CubeSat.
And Spain is developing HERA’s advanced guidance, navigation and control system as well as the deep-space communication system. It is also providing the JUVENTAS gravimeter instrument.
• Austria is supporting with mission data analysis and processing
• Denmark is contributing to the JUVENTAS CubeSat and remote terminal unit
• France is providing JUVENTAS’ low-frequency radar, as well as star trackers and support to the CubeSats’ payload operations planning and close-proximity trajectories
• Hungary is supporting scientific calibration of the cameras
• The Netherlands is developing the new deep-space CubeSat deployment system and providing HERA’s sun sensors
• Switzerland is contributing with structural elements and mechanisms for the solar arrays
• Finland is providing the second CubeSats’ multi-spectral imager and onboard equipment, as well as the data processing unit
• Poland is contributing with JUVENTAS’ low-frequency radar deployable antennas
• Ireland is providing an innovative inertial measurement unit for HERA, to support deep-space navigation
• Latvia (an ESA associate member state) is contributing a time-of-flight detector for the mission’s laser altimeter