ESA Sends Hera Probe Into Space On Planetary Defence Mission

The European Space Agency’s (ESA) Hera mission has launched from Cape Canaveral in Florida to study the aftermath of a NASA probe that intentionally slammed into an asteroid two years ago.

Hera, along with its two shoebox-sized satellites, launched aboard a SpaceX Falcon 9 rocket at 10:52 am local time (15:52 BST) on Monday.

The flight was Falcon 9’s first since the US Federal Aviation Administration (FAA) grounded the rockets due to an anomaly during SpaceX’s Crew 9 mission on 29 September.

The FAA is continuing to investigate that issue, but authorised the Hera launch on a one-off basis.

Crash-site investigation

The mission is set to reach the asteroid Dimorphos in late 2026, after passing by Mars in mid-March 2025 in order to gain extra momentum.

Dimorphos, a small body about the size of the Pyramid of Giza which orbits a larger mountain-sized asteroid named Didymos, was the target of NASA’s DART mission two years ago.

The US agency’s Double Asteroid Redirection Test (DART) mission was aimed at testing whether a probe could redirect a potentially hazardous near-Earth object (NEO) by impacting with it at 13,645 miles per hour.

The asteroids do not pose a threat to Earth, but were seen as ideal for testing planetary defence technologies.

Since the DART test astronomers have monitored the aftermath of the impact using Earth-based telescopes, and have determined that the probe successfully shifted the body’s orbital period, adding about 32 or 33 minutes to its orbital period.

Hera is intended to provide further information, such as how great an effect the probe’s impact had on the asteroid, which could help scientists further refine planetary defence technology.

At the time the Hera probe arrives at the double-asteroid system it is expected to be about 121 million miles from Earth.

Planetary defence

Hera is to initially spend six weeks observing both asteroids, after which it will release its two small satellites, Juventas and Milani, which have radar and multispectral imaging instruments capable of providing an in-depth analysis of the space rocks.

Hera will come as close as 0.6 miles from the asteroids’ surface, passing over the DART impact crater multiple times, and may eventually land on Didymos, while the satellites may land on Dimorphos.

The analyses may help scientists learn if the rocks are, for instance, groups of rubble held together by gravity or if they have a solid core surrounded by boulders and gravel.

The investigations may provide insights about similar space objects that occasionally impact with Earth, such as a house-sized asteroid that in 2013 exploded over the town of Chelyabinsk in Russia, blowing out windows for hundreds of square miles and injuring more than 1,600 people.

The ultimate goal of space defence programmes is to be able to detect such impacts before they occur and minimise the potential risk.