On July 16, 1994, astronomers were in awe as the first of numerous pieces of the Shoemaker-Levy 9 comet collided with Jupiter with an extraordinary impact 30 years ago. The event prompted a significant amount of interest in the field of planetary defense, as people inquired whether it was possible to prevent such an occurrence from happening on Earth.
On July 16, the European Space Agency’s (ESA) Space Safety program made another stride toward addressing this issue. The Rapid Apophis Mission for Space Safety (Ramses) is the next planetary defense mission for which the program has been granted permission to commence preparatory work.
In 2029, Ramses will meet the asteroid 99942 Apophis and accompany it during its safe but exceptionally near flyby of Earth. Researchers will examine the asteroid’s physical characteristics as Earth’s gravitational pull changes them. Their findings will enhance our capacity to safeguard our planet from a comparable object on the brink of colliding with it.
Asteroid Apophis
On April 13, 2029, the asteroid Apophis, which is approximately 375 meters in diameter and approximately the size of a cruise liner, will pass within 32,000 kilometers of Earth’s surface. For a brief period, it will be visible to the unaided eye in clear, dark skies for approximately two billion people across a significant portion of Europe, Africa, and Asia.
Apophis will not collide with Earth for at least the next 100 years, as astronomers have disregarded the possibility of a collision. However, the Apophis flyby in April 2029 is a highly uncommon natural phenomenon. Astronomers estimate that an asteroid of this magnitude approaches Earth only once every 5,000 to 10,000 years, as determined by examining the diameters and orbits of all known asteroids. By comparison, a total solar eclipse occurs approximately every 18 months on Earth, and Comet Halley returns to the Earth’s skies every 76 years.
The 2029 Apophis flyby will be a unique opportunity for public engagement, planetary defense, and science, and it will capture the attention of the entire globe.
Ramses Spacecraft
Before passing Earth, the ESA’s Ramses spacecraft will rendezvous with Apophis and escort the asteroid during the flyby to observe the impact of our planet’s gravity on its shape and movement.
Patrick Michel, the Director of Research at CNRS at the Observatoire de la Côte d’Azur in Nice, notes that there is still much to discover about asteroids. However, up until now, we have been required to travel deep into the Solar System to study them and conduct experiments on their surface.
He further stated that for the first time in history, nature is presenting and conducting an experiment. Patrick Michel, the Director of Research at CNRS at the Observatoire de la Côte d’Azur in Nice, notes that there is still a great deal that we have yet to discover about asteroids. However, up until now, we have been required to travel deep into the Solar System to study them and conduct experiments on their surface.
He further stated that for the first time in history, nature is presenting and conducting an experiment. All we need to do is observe as Apophis is stretched and squeezed by strong tidal forces, which may trigger landslides and other disturbances, and disclose new material from beneath the surface.
Ramses must launch in April 2028 to arrive at Apophis in February 2029, two months before the near approach. To ensure the deadline is met, ESA requested authorization to commence the mission’s preparatory work as soon as feasible, utilizing existing resources. The Space Safety Programme Board has authorized this action. The decision to fully commit to the mission will be made at the Ministerial Council meeting of ESA in November 2025.
The spacecraft will perform a comprehensive before-and-after survey of the asteroid’s shape, surface, orbit, rotation, and orientation using a variety of scientific instruments. Scientists will gain a wealth of knowledge about the asteroid’s composition, interior structure, cohesion, mass, density, and porosity by examining the changes in Apophis during the flyby. These are all critical attributes for determining the most effective method of diverting a hazardous asteroid from a collision course with Earth. Data from Ramses will also provide new scientific insights into the formation and evolution of the Solar System, as asteroids are also time archives that were formed over four billion years ago.
In the interim, NASA has redirected its OSIRIS-REx spacecraft to Apophis. Due to the constraints of orbital mechanics, the newly renamed OSIRIS-APEX will arrive at Apophis approximately one month after the asteroid’s Earth flyby.
According to researchers, Earth’s tidal forces are expected to affect the asteroid’s rotational condition, potentially causing landslides and earthquakes. Having Ramses present in advance will obtain a comprehensive “before and after” analysis of the impact of the near encounter on Apophis. Subsequently, the presence of two highly capable spacecraft at Apophis following the flyby will facilitate the measurement of long-term effects and the conduct of additional scientific investigations.