Hera planetary defense mission begins

The European Space Agency’s (ESA) first planetary defense spacecraft has left planet Earth. The mission of the Hera space probe is to inspect a unique target among the more than 1.3 million known asteroids in our solar system: the only body whose orbit has been modified by human action. The inspection aims to find out the details of said deviation.

With this mission, Hera will help increase Earth’s security by improving scientific knowledge on the kinetic impact asteroid deflection technique. The mission is part of a more ambitious initiative: turning terrestrial asteroid impacts into a type of completely avoidable natural catastrophe.

Developed within the framework of ESA’s Space Security program, Hera took off aboard a SpaceX Falcon 9 rocket from the Cape Canaveral Space Center (Florida, USA) on October 7 at 10:52 local time (16:52 CEST, 14:52 UTC) and its solar panels were deployed an hour later.

The car-sized Hera will carry out the first detailed study of a “binary” – or double-body – asteroid, 65803 Didymos, which is orbited by a smaller body, Dimorphos. Hera will focus primarily on the smaller of the two, whose orbit around the larger asteroid was modified by NASA’s DART (Double Asteroid Redirection Test) mission, which demonstrated the deflection of asteroids by kinetic impact in 2022.

Hera will also conduct deep space technology experiments, such as deploying two shoebox-sized CubeSats to approach the target asteroid and maneuver in ultra-low gravity to obtain additional scientific data before landing. The lead ship will also attempt to autonomously navigate around the asteroids based on visual tracking.

Artistic recreation of Hera and her CubeSats connected to each other via radio telecommunication links. (Image: ESA Science Office)

ESA’s European Space Operations Center in Darmstadt, Germany, oversaw the launch and will now oversee the remainder of the journey.

ESA, together with NASA and other partner agencies, keeps an eye on the sky to identify and track dangerous asteroids. But if the arrival of an asteroid were detected, what could be done to stop it?

NASA’s DART mission was created to help answer that question. On September 26, 2022, the DART spacecraft performed humanity’s first asteroid bypass by intentionally crashing into Dimorphos, the large pyramid-sized moon of the larger, mountain-sized asteroid Didymos, changing its orbit. .

Based on observations made from Earth, DART managed to reduce Dimorphos’ orbital period around Didymos by 33 minutes, almost 5% of its original value, while throwing a plume of debris thousands of kilometers into space.

However, there are still many unknowns to be resolved before this method of kinetic impact deflection of asteroids becomes a well-known and reliable planetary defense technique. What was the size of the crater left by the DART impact, or did the entire asteroid undergo a remodeling? What is the mineralogy, structure and exact mass of Dimorphos?

With a cube-shaped main body approximately 1.6 meters in diameter and flanked by twin 5-meter solar wings, the Hera space probe is ESA’s own contribution to this international planetary defense collaboration. Once it reaches the binary asteroid Didymos in two years, the spacecraft will carry out an investigation of the effects of the impact from very close range to gather all the necessary missing knowledge.

“Hera’s ability to closely study its asteroid target will be just what is needed for operational planetary defense,” explains Richard Moissl, director of ESA’s Planetary Defense Office. “We can imagine a scenario where a reconnaissance craft is quickly sent to an asteroid to assess whether any follow-up deflection action is necessary. “We will soon practice this again with our Ramses spacecraft, which should encounter the asteroid Apophis during its approach to Earth in 2029.”

Around 100 European companies and institutes from 18 ESA member states have participated in the development of the Hera mission. OHB System AG led the industrial consortium, including responsibility for the overall spacecraft design, development, assembly and testing.

Hera will conduct the most detailed exploration to date of a binary asteroid system. Although binary asteroids represent 15% of all known asteroids, none of them have ever been studied in detail. In addition, the asteroid Dimorphos is the smallest body visited so far on a space mission.

The CubeSat Milani, developed for ESA by Italian industry led by Tyvak International, will study the mineral composition of Dimorphos and the dust surrounding it, while the CubeSat Juventas, produced by a Luxembourg-led consortium within the framework of GOMspace, will carry out the first radar survey of the subsurface of an asteroid. Toward the end of its six-month period studying asteroids, Hera will also test an experimental mode of self-propulsion that will allow it to navigate around asteroids autonomously based on tracking surface features.

ESA’s Hera mission scientist Michael Kueppers comments: “At the end of the Hera mission, the Didymos pair should become the best-studied asteroids in history, helping to protect Earth from the threat of incoming asteroids. ».

On its journey, Hera will pass very close to Mars in March 2025. This will give the ship additional speed to reach its final goal: Didymos. This maneuver on Mars is of the type known as gravitational assist. Hera will take advantage of its passage near Mars and its satellites to observe the Martian moon Deimos, deploying its instruments for scientific use for the first time.

Arrival at Didymos is scheduled for autumn 2026. This will be when the mission will enter its main phase. (Source: ESA)