Europe takes the lead in planetary defence

04.23.2026, by

Reading time: 8 minutes

Illustration of the Ramses mission, which in 2028 will set off for the asteroid Apophis.

The Ramses mission to asteroid Apophis is set to launch in 2028. It forms the cornerstone of a planetary defence programme designed to protect our planet from the risk of collision with near-Earth objects.

The countdown to the launch in early 2028 of the European Space Agency's (ESA) new mission, Ramses1, has begun. The aim of the project, conducted in collaboration with the Japanese space agency (JAXA), is to study one of the most eagerly-awaited astronomical events of the coming decade, the extremely close approach to Earth of the asteroid Apophis on Friday, 13 April, 2029. On that day, the asteroid will fly past our planet at a closest distance of a mere 31,600 km, less than that of orbiting geostationary telecommunications satellites (approximately 36,000 km).

This unprecedented encounter will not go unnoticed. Apophis will be visible to the naked eye across most of Europe and Africa, allowing more than two billion people to observe it, provided the night skies are clear. As well as being spectacular, "this flyby of the Earth is also a crucial natural experiment that will help improve the defences of our planet against any asteroids that might impact it," explains Patrick Michel, an astrophysicist at the JL Lagrange laboratory2 in Nice (southeastern France), and lead scientist for the new mission.

A first mission

Long confined to the realm of science fiction, preventive measures against the risk of collision between our planet and an asteroid have now become reality. Since 2019, ESA has been developing its Space Safety Programme, part of which is devoted to asteroid impact prediction and prevention. It aims to monitor and study potentially dangerous bodies, and to devise strategies capable of averting such threats.

The programme already has a first mission under its belt, namely Hera. Launched in 2024, it will be a full-scale test of the deflection of the asteroid Dimorphos, located about 11 million kilometres from Earth, caused by the impact of NASA’s DART3 spacecraft.

Virtual reality view of the Hera spacecraft… in a living room.

An asteroid the size of the Eiffel Tower

Ramses is the programme's second mission. "Apophis is a near-Earth object, an asteroid whose orbit around the Sun occasionally crosses that of the Earth. Objects of this type could potentially collide with our planet," says Benoit Carry, an assistant astronomer and asteroid specialist at the Observatoire de la Côte d'Azur, also in in Nice.

Another distinctive feature of Apophis is that it is a relatively large asteroid. It has a diameter of around 330 m (the height of the Eiffel Tower) and an estimated weight of some 40 to 50 million tonnes. "The arrival of such a large body so close to our planet is a rare event, one that occurs only once every few thousand years," the astronomer points out. Besides, Apophis is travelling at very high speed – around 12 kilometres per second.

If such an object were to strike the Earth, "it would form a crater 8 to 10 times its own size, in other words about 2.5 km across", Carry explains. This would be enough to cause "a major catastrophe if it struck an urban area, or else a devastating tsunami if it impacted an ocean. Not to mention the huge amount of dust that would be ejected into the atmosphere, and would cause the climate to cool". According to Michel, "the damage would be on the scale of an entire country".

Radar images of the asteroid Apophis, during its closest approach to Earth, on 8, 9 and 10 March 2021. In 2029, it will pass even closer.

“A unique scientific opportunity”

Shortly after Apophis was discovered in 2004 by researchers at the University of Hawaii (US) specialising in asteroid studies, astronomers worked out that it had a 1 in 37 (or 2.7%) chance of striking Earth in 2029. This was "the highest probability of collision ever estimated for an asteroid", Carry says, which is why it was named after Apophis, the Egyptian god of chaos and destruction.

Fortunately, in the weeks that followed, more precise observations and calculations ruled out any risk of collision with the asteroid, not only in 2029, but also for at least another century.

So, if Apophis's very close flyby of Earth in 2029 no longer poses a danger, why bother to study it? "Because it provides us with a unique scientific opportunity to better understand the physical properties of the asteroid (its mass, density, porosity, internal structure, etc.) and how these evolve as a result of the Earth's gravitational pull," Michel explains.

Countering potentially dangerous asteroids

In fact, researchers expect that, once the two bodies are in close proximity, tidal forces due to Earth's gravity will stretch and compress Apophis. This could trigger landslides on the asteroid's surface, or even internal vibrations. In addition, its orbit and rotation period should undergo slight changes.

“As well as improving our understanding of asteroids, the study of Apophis's properties and behaviour at its closest point to Earth could also help define the best strategies to neutralise these potentially dangerous objects,” Michel adds. “For example, measuring its response to external forces, represented here by Earth's tidal forces, and determining its degree of porosity, in other words whether its interior contains a lot of empty space or not, will help ascertain the force required to strike a similar body and effectively deflect it from Earth's trajectory."

Schedule for the various stages of the Hera mission.

In practice, the mission will rely on a two-metre-wide spacecraft, whose design will be inspired by that of the Hera probe. "Like Hera, Ramses will comprise a primary spacecraft and two cubesats (miniature satellites) each weighing 12 kg, one of which will be deployed near Apophis while the other lands on the asteroid," Michel explains. However, "as it will be operating closer to the Sun, its solar panels will be smaller. And, to enable it to reach Apophis and remain in its vicinity, it will be equipped with larger tanks able to hold 33% more fuel".

A three-part, high-tech probe

In order to achieve its goals, Ramses will carry several instruments. One of these is a hyperspectral camera (able to capture images by using a large number of adjacent spectral bands), which will make it possible to determine the asteroid's chemical composition. Another high-resolution colour camera will take images of it with a resolution of about 10 cm, and will be able to detect any possible changes on its surface. Finally, a plasma spectrometer will analyse the environment of charged particles around the asteroid, related to its passage through the Earth's magnetosphere (the region of space under the influence of our planet's magnetic field).

The cubesat designed to be deployed near Apophis will carry a dust detector and analyser capable of establishing its chemical composition, as well as a low-frequency radar, which will probe the interior of the asteroid. As for the cubesat due to land on it, it will be equipped with a gravimeter to measure its gravitational field, as well as a seismograph to analyse the propagation of seismic waves and reveal the celestial body's internal structure.

"The radar in the first cubesat and the seismograph in the second are two French contributions," Michel points out. "They demonstrate France's world-renowned expertise in determining the internal structure of asteroids."

Image from Armageddon the film, 1998 (if an asteroid collides Paris)

Fears of an asteroid colliding with Earth are a popular theme in cinema – seen here, a still from the film “Armageddon” (1998).

Six months with Apophis

Ramses is scheduled to launch between 20 April and 15 May, 2028 from the Japanese island of Tanegashima, aboard a JAXA H3 launch vehicle. It will take ten months to get to Apophis, beginning its approach phase in February 2029, two months before the asteroid reaches its closest point to Earth.

The cubesat carrying the radar will be deployed in March 2029, while the one due to land on Apophis will do so a few days before the celestial body's closest approach to Earth. Ramses will then remain in the vicinity until August 2029.

The spacecraft will therefore accompany Apophis for at least six months, which will give it plenty of time to measure its physical properties and behaviour before, during and after its encounter with our planet.

The trajectory of OSIRIS-APEX on 23 September 2025.

Europe and Japan on the front line

Ramses should be joined by the American OSIRIS-APEX probe4, which is also set to investigate Apophis in 2029, although this spacecraft will not reach it until about a month after its nearest flyby of Earth. As a result, it will miss this historic rendezvous with the asteroid. Ramses therefore puts ESA and JAXA on the front line when it comes to characterising Apophis during its unique encounter with our planet.

"If Ramses is a success, it will confirm that Europe can rapidly launch a reconnaissance mission to an approaching asteroid – bearing in mind that, as with Hera, it took just four years to set up this space mission, instead of the normal average of 15 years," Michel concludes. "Such swift action would play a crucial role by giving us enough time to study a potentially dangerous body and find a way of shielding our planet before the collision takes place."