07/16/2024
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Thirty years ago, on July 16, 1994, astronomers watched in amazement as the first of many pieces of Comet Shoemaker-Levy 9 slammed into Jupiter with incredible force. The event sparked a surge of interest in planetary defense, with people asking, “Is there anything we can do to prevent this from happening to Earth?”
Today, ESA’s Space Security programme has taken another step towards answering this question. The programme has been given permission to start preparatory work on its next planetary defence mission: the Apophis Fast Mission for Space Security (Ramses).
Ramses will rendezvous with asteroid 99942 Apophis and accompany it on its safe but unusually close flyby of Earth in 2029. Researchers will study the asteroid as Earth’s gravity changes its physical characteristics. Their findings will improve our ability to defend our planet against any similar objects on a collision course in the future.
Apophis
The asteroid Apophis, about 375 m in diameter and about the size of a cruise ship, will pass within 32,000 km of the Earth’s surface on April 13, 2029. For a short time, it will be visible to the naked eye, in clear, dark skies, to about two billion people in much of Europe, Africa and parts of Asia.
Apophis will miss Earth: Astronomers have ruled out any possibility of the 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 estimate that an object of this size approaches Earth only once every 5,000 to 10,000 years. For 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 2029 Apophis flyby will attract worldwide attention and represents a unique opportunity for science, planetary defense and public engagement.
Apophis’ orbit deflected by Earth’s gravity – NEO Toolkit
Ramses
ESA’s Ramses spacecraft will rendezvous with Apophis before it passes close to Earth and will accompany the asteroid during the flyby to observe how it is distorted and changed by our planet’s gravity.
Patrick Michel, CNRS research director at the Côte d’Azur Observatory in Nice, comments: “We still have a lot to learn about asteroids, but until now we have had to travel deep into the Solar System to study them and carry out experiments ourselves to interact with their surface.”
“For the first time, nature has brought us one and conducted the experiment itself. All we have to do is watch Apophis stretch and compress under strong tidal forces that can trigger landslides and other disturbances and reveal new material beneath the surface.”
ESA’s Ramses mission to the asteroid Apophis
Ramses is scheduled to be launched in April 2028 to allow for arrival at Apophis in February 2029, two months before the approach point. In order to meet this deadline, ESA has requested permission to start preparatory work for the mission as soon as possible using existing resources. This permission has been granted by the Space Safety Programme Steering Committee. The decision to fully commit to the mission will be taken at the ESA Ministerial Council meeting in November 2025.
Using a suite of scientific instruments, the spacecraft will conduct a comprehensive pre- and post-flyby study of the asteroid’s shape, surface, orbit, rotation, and orientation. By analyzing Apophis’ changes during the flyby, scientists will learn a great deal about an asteroid’s response to external forces, as well as its composition, internal structure, cohesion, mass, density, and porosity.
These properties are very important for assessing how best to prevent a dangerous asteroid from hitting Earth. Since asteroids are also time capsules formed more than four billion years ago, Ramses data will also provide new scientific insights into the formation and evolution of the solar system.
Apophis radar observations rule out future impact
NASA has redirected its OSIRIS-REx spacecraft to Apophis. Due to limitations in orbital mechanics, the new OSIRIS-APEX spacecraft will arrive at Apophis about a month after the asteroid’s flyby of Earth.
Researchers predict that Earth’s tidal forces could alter the asteroid’s rotational state and trigger earthquakes and landslides. Having Ramses there in advance will provide a detailed “before and after” view of how Apophis was altered by its close encounter. Then, after Apophis’ flyby, the presence of two high-performance spacecraft will allow for additional scientific research and measurement of long-term effects.
Rapid Reconnaissance: A Cornerstone of Planetary Defense
The international collaboration between NASA’s DART asteroid impactor and ESA’s Hera asteroid sleuth demonstrates that, in principle, humanity can redirect an asteroid if necessary. But to respond to a real threat, we need to be able to design and deploy a rapid response.
Richard Moissl, Head of ESA’s Planetary Defence Office, explains: “Ramses will demonstrate that humanity is capable of deploying a reconnaissance mission to reach an approaching asteroid in just 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 analyse the orbit and structure of the approaching asteroid. The results would be used to determine how best to redirect the asteroid or rule out non-impacts before developing a costly deflection mission.”
Paolo Martino, ESA Ramses mission manager, added: “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 strict deadlines and Ramses will follow suit.”
Hera approaches asteroid Didymos