According to the ESA Near Earth Object Coordination Center (NEOCC), 35,264 Known asteroids regularly cross the orbit of Earth and other inner planets. Of these, 1.626 have been identified as Potentially dangerous asteroids (PHAs), meaning they could one day pass close enough to Earth to be caught by its gravity and impact its surface. While planetary defense has always been a concern, the comet Shoemaker's tax 9 The collision with Jupiter in 1994 sparked intense interest in this field.
In 2022, NASA Double asteroid redirection test The mission (DART) successfully tested the kinetic impact method when it collided with Dimorphos, the small asteroid orbiting Didymos. Today, the ESA Space Safety The program is taking steps to test the next planetary defense mission: the Apophis fast mission for space safety (RAMSES). In 2029, RAMSES will encounter the near-Earth asteroid (NEA) 99942 Apophis and accompany it on its very close (but safe) flyby of Earth in 2029. The data it collects will help scientists improve our ability to protect Earth from similar objects that could pose an impact risk.
Discovered in 2004, Apophis is an irregularly shaped asteroid measuring about 375 m (410 yd) in diameter. At the time, observations indicated there was a small risk of it impacting Earth in 2029, 2036, or 2068. Given its size and the devastating effect an impact would have, astronomers decided to name it after the Egyptian god of chaos and destruction. Although astronomers have since ruled out the possibility of a collision for at least the next century, Apophis will pass within 32,000 km (~19,885 mi) of Earth's surface on April 13, 2029.
At this distance, the asteroid will be close enough to be visible to the naked eye to about two billion people across much of Europe, Africa and parts of Asia. Based on analyses of the size and orbits of all known asteroids, astronomers believe that objects of this size pass this close to Earth only about once every 5,000 to 10,000 years. The RAMSES spacecraft will encounter Apophis before it makes its closest pass by Earth and track it, monitoring it with a suite of scientific instruments to see how Earth’s gravity changes it.
The goal is to conduct before-and-after studies of the asteroid's shape, surface, orbit, rotation, and orientation. Based on this comparative analysis, scientists will learn more about how an asteroid's fundamental characteristics—its composition, internal structure, cohesion, mass, density, and porosity—respond to external forces. These properties are vital to determining how to deflect a PHA from its course so that it does not collide with Earth. Patrick Michel, research director at tohe National Center for Scientific Research (CNRS) and the Côte d'Azur Observatory in Nice, explained in an ESA article Press release:
“We still have a lot to learn about asteroids, but so far we have had to travel deep into the Solar System to study them and perform experiments to interact with their surface. For the first time, nature is bringing one to us and performing the experiment itself. All we have to do is watch as Apophis is stretched and compressed by strong tidal forces that can trigger landslides and other disturbances and reveal new material from beneath the surface.”
ESA recently received permission from the Space Safety Programme Board to begin preparatory work on the mission so it can launch in April 2028. This deadline is necessary, so the mission must be ready to launch and rendezvous with Apophis in orbit in February 2029. A final decision to commit to the mission will be made at the ESA meeting. Meeting of the Ministerial Council in November 2025. In the meantime, NASA has re-directed its newly renamed APEX OSIRIS spacecraft toward Apophis, arriving a month after the asteroid makes its flyby.
Since asteroids are leftover material from the formation of the Solar System (about 4.5 billion years ago), this encounter is also an opportunity to obtain data that could provide new insights into planetary formation and evolution. This makes the 2029 flyby an extremely rare opportunity for astronomy, asteroid science, planetary defence and to engage billions of people around the world. It will also be an opportunity for international collaboration, as DART and the ESA programme have already demonstrated. Hera missions: the first redirected to Didymos while the second confirmed a change of orbit.
Last but not least, the RAMSES mission will test the ability of space agencies to rapidly build and deploy an asteroid response. As Richard Moissl, head of ESA's asteroid response programme, Planetary Defense Officeexplained:
“Ramses will demonstrate that humanity can send a reconnaissance mission to rendezvous with an asteroid within a few years. This type of mission is a cornerstone of humanity’s response to a hazardous asteroid. A reconnaissance mission would first be launched to analyze the asteroid’s orbit and structure. The results would be used to determine how best to reroute the asteroid or rule out potential impacts before developing a costly deflection mission.”
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