Germany is the largest contributor to the mission. The German Space Agency at the German Aerospace Center coordinates the German ESA contributions with funds from the Federal Ministry for Economic Affairs and Climate Protection. DLR is involved scientifically with the DLR Facility for Space Operations and Astronaut Training in Cologne and the DLR Institute for Planetary Research in Berlin. The Hera space probe was developed and built at OHB in Bremen. Hera will use an antenna newly developed in Germany to send its data to Earth. Two cameras from Jena provide images of Didymos and Dimorphos.
Asteroid impacts on Earth are very rare today, but can have serious consequences. On February 15, 2013, around 1,500 people were injured when a small asteroid twenty meters in diameter entered the Earth’s atmosphere near the Russian city of Chelyabinsk. Most of it evaporated, but when it exploded at a height of around thirty kilometers, its remnants triggered a pressure wave that shattered countless window panes in the city of over a million inhabitants. They were the cause of the injuries.
“Chelyabinsk was an event that can serve as a reminder to us. In order to prevent dangerous events in the future, we need the data from the Hera mission,” explains Manuel Metz, Hera project manager at the German Space Agency. “The consequences of the impact of a larger celestial body would be much more severe. They could even threaten entire ocean coasts or continents. “That would have existential consequences for the continued existence of humanity,” emphasizes Stephan Ulamec from the DLR Facility for Space Operations and Astronaut Training, who is scientifically involved in Hera. “This is demonstrated not least by the remains of the almost two hundred kilometer wide Chicxulub crater in what is now Mexico.”
The good news: None of the approximately 36,000 known NEOs – Near Earth Objects – with a diameter of more than a hundred meters are currently on a collision course with the Earth. The asteroid Apophis, discovered in 2004, will pass Earth in 2029. During its flyby, at 31,750 kilometers above the surface, it comes closer to it than satellites in geostationary orbit. It has a diameter of around 350 meters, which would have extreme consequences in the event of an impact. Based on current knowledge, such a collision can be ruled out for the 21st century. However, the fact that it passes so close to Earth shows that we must always be prepared for such objects.
In order to develop methods with which humanity can effectively counter such dangers, NASA and Esa are carrying out the “Asteroid Impact & Deflection Assessment” AIDA cooperation. It consists of the NASA DART mission and the ESA Hera mission. It started with DART, the “Double Asteroid Redirection Test”. The double asteroid Didymos and Dimorphos was chosen as the target, with the significantly smaller Dimorphos with a diameter of around 150 meters orbiting the 800 meter large Didymos as an asteroid moon.
The aim was to influence the orbital period of both asteroids around each other. For this purpose, DART hit Dimorphos in a controlled manner on September 26, 2022 at a speed of over six kilometers per second. Measurements with telescopes determined that Dimorphos’ orbital period had been shortened by 33 minutes from the original 11 hours 55 minutes – previously modeled was only ten minutes.
Hera is now sent on her way to the double asteroid to investigate how exactly the orbital period and shape of the asteroids have changed. For this purpose, the probe is equipped with twelve measuring instruments. Among the most important are the two Asteroid Framing Cameras, two redundant, monochromatic cameras built in Jena that are used to determine the position of the space probe in the asteroid system. They are essential for the navigation of the probe and will also contribute to the study of asteroids.
The Hera team will use the images from the framing cameras to calculate a digital terrain model of the asteroids and search for changes on Dimorphos that were caused by the DART impact. “Did a crater form on Dimorphos? Has the entire asteroid been altered? Was the surface of Didymos also hit by ejecta? We want to answer these questions with our digital terrain model,” says the scientific director of the cameras, Jean-Baptiste Vincent from the DLR Institute of Planetary Research.
Hera also carries two CubeSats, Juventas and Milani, each the size of a shoebox. They will observe Dimorphos up close and even land on the asteroid in the final phase of the mission to measure its surface, internal structure and gravity. The measurements are intended to determine the exact mass of Dimorphos, which was previously determined by the AFCs. Determining the mass is necessary to understand exactly how effective the DART deflection was.
The data obtained can then be used to calculate how the deflection from other celestial bodies can be achieved. In the event of an asteroid on an actual collision course, this will be the basis of a true planetary deflection mission. In addition, the data collected will represent another milestone for asteroid research in general.
Germany is the largest contributor to the Esa mission with around 130 million euros, or 37 percent of the total. The Hera probe was developed and built by the company OHB SE in Bremen. A newly developed antenna made of carbon fiber reinforced plastic comes from the Munich company HPS. The two asteroid framing cameras come from Jena-Optronik. The TU Dresden is significantly involved in the development of the radar experiment on the Cubesat Juventas. In addition, researchers from Germany are involved in the Hera Science team to scientifically evaluate the data obtained from the mission.
DLR / RK
