Introducing Ramses, ESA’s mission to the asteroid Apophis

Today, ESA’s Space Security Program took another step towards answering this question. The program received permission to begin preparatory work for its next planetary defense mission – the Rapid Apophis Mission for Space Safety (Ramses).

Ramses will encounter asteroid 99942 Apophis and accompany it during its safe but exceptionally close flyby of Earth in 2029. Researchers will study the asteroid to see how Earth’s gravity changes its physical properties. Finding them will improve our ability to defend our planet against any similar object found to be on a collision course in the future.

Apophis

Asteroid Apophis with a diameter of 375 m, the size of a cruise ship, will fly by on April 13, 2029 at a distance of 32,000 km from the Earth’s surface. It will be visible to the naked eye for a short time in clear and dark skies for about two billion people across much of Europe and Africa and parts of Asia.

Apophis to miss Earth: Astronomers have ruled out any chance of an asteroid colliding with our planet for at least the next 100 years. But the Apophis flyby in April 2029 is an extremely rare natural phenomenon.

By analyzing the sizes and orbits of all known asteroids, astronomers believe that an object this large approaches Earth only once every 5,000 to 10,000 years. By comparison, a total solar eclipse occurs somewhere on Earth about once every 18 months, and Halley’s Comet returns to Earth’s sky every 76 years.

The Apophis flyby in 2029 will attract worldwide attention and represent a unique opportunity for science, planetary defense and public engagement.

Ramses

ESA’s Ramses spacecraft will encounter Apophis before it passes Earth and will accompany the asteroid during the flyby to watch it being warped and altered by our planet’s gravity.

Patrick Michel, Director of Research at the CNRS at the Observatoire de la Côte d’Azur in Nice, comments: “There is still so much to learn about asteroids, but until now we have had to travel deep into the Solar System to study. and we ourselves conduct experiments to interact with their surface.’

“For the first time ever, nature brings us one and performs the experiment herself. All we have to do is watch Apophis being stretched and squeezed by strong tidal forces that can trigger landslides and other disturbances and expose new material from beneath the surface.”

Ramses must launch in April 2028 to allow for a flyby of Apophis in February 2029, two months before close approach. In order to meet this deadline, ESA requested permission to begin preparatory work on the mission as soon as possible using existing resources. This clearance was granted by the Space Safety Program Board. A decision on whether to fully commit to the mission will be made at the ESA Ministerial Council meeting in November 2025.

Using a suite of scientific instruments, the probe will conduct a thorough before-and-after survey of the asteroid’s shape, surface, orbit, rotation and orientation. By analyzing how Apophis changes during the flyby, scientists will learn a lot about the asteroid’s response to external forces, as well as the asteroid’s composition, internal structure, cohesion, mass, density and porosity.

These are all very important properties for assessing how best to knock a dangerous asteroid off a collision course with Earth. Since asteroids are also time capsules formed more than four billion years ago, data from Ramses will also offer new scientific insights into the formation and evolution of the Solar System.

Meanwhile, NASA redirected its OSIRIS-REx spacecraft towards Apophis. Due to the limits of orbital mechanics, the newly renamed OSIRIS-APEX will arrive at Apophis about a month after the asteroid’s flyby of Earth.

Researchers hypothesize that Earth’s tidal forces will alter the asteroid’s rotational state, possibly triggering tremors and landslides. Having Ramses there beforehand will provide a detailed “before and after” look at how Apophis was changed by his close encounter. Then, as a result, having two highly capable spacecraft at Apophis after the flyby will allow for further scientific investigations and measurements of long-term effects.

Rapid Exploration: The cornerstone of planetary defense

An international collaboration between NASA’s DART asteroid impactor and ESA’s Hera asteroid probe shows that, in principle, humanity can redirect an asteroid if needed. However, in order to respond to a real threat, we must be able to quickly create and deploy a response.

Richard Moissl, head of ESA’s Planetary Defense Office, explains: “Ramses will demonstrate that humanity can deploy a probe mission to rendezvous with an incoming asteroid within a few years. This type of mission is the cornerstone of humanity’s response to a dangerous asteroid. First, a reconnaissance mission would be launched to analyze the trajectory and structure of the incoming asteroid. The results would be used to determine how best to redirect the asteroid or rule out misses before a costly deflector mission is developed.

Paolo Martino, head of ESA’s Ramses effort, adds: “The Ramses mission concept reuses much of the technology, expertise and industrial and scientific communities developed for the Hera mission. Hera has demonstrated how ESA and European industry can meet tight deadlines and Ramses will follow suit .”