In an official statement issued on July 16, 2024, ESA declared that its Space Safety Programme received the green light to prepare a new planetary defense mission, the Rapid Apophis Mission for Space Safety (Ramses). The mission aims to send a spacecraft to rendezvous with the asteroid 99942 Apophis two months before its close encounter with the Earth in April 2029 and follow it during and after the flyby.
Ramses will be equipped with scientific instruments developed for the Hera mission, collecting data to understand how the Earth’s gravity can alter the physical characteristics of the asteroid while skimming the planet at around thirty thousand kilometers from the surface. Measuring those values before and after the event will be a unique chance to learn more about these celestial bodies, improving the Space Safety Programme’s abilities to develop and adopt planetary defense actions.
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Apophis, a missed threat to our planet
Apophis is a stony-type NEA (Near Earth Asteroid), 375 meters wide, discovered twenty years ago on June 19, 2004, and named after the Egyptian god of chaos and destruction. Some months after its discovery, the initial observations used to calculate its potential trajectory provided a 2.7% probability of impact with the Earth for its encounter on April 2029.
The collision of such an asteroid could result in the release of over a thousand megatons of energy and widespread destruction extending up to several hundred kilometers from its impact site. This huge potential damage and the impact probability put Apophis at the top of the Torino Impact Hazard Scale, as the most hazardous object ever discovered.
Later observations lowered the impact probability for the 2029 rendezvous to zero, removing Apophis from the Torino scale. Nevertheless, the 2029 encounter will be an exceptional event since asteroids of that size approach the Earth once every five to ten thousand years.
Apophis will pass at just thirty-two thousand kilometers from the Earth’s surface, closer than geostationary orbit, and will be visible to the naked eye in clear skies in the Eastern Hemisphere, Europe included, drawing the attention of the scientific community and the entire world.
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Hera spacecraft technology for a rapid reconnaissance mission
Scheduled to launch in October 2024, ESA’s Hera Mission will examine the Didymos binary asteroid system, after the voluntary impact of the DART spacecraft into the little moon Dymorphos to test the first asteroid deflection strategy ever. Due to the similar scope of the two missions, Hera’s technology will be used to build the Ramses spacecraft, minimizing its development time and cost.
“The Ramses mission concept reuses much of the technology, expertise, and industrial and science communities developed for the Hera mission. Hera demonstrated how ESA and European industry can meet strict deadlines and Ramses will follow its example.”
— Paolo Martino, ESA System Engineer for Ramses Mission
The heritage of Hera will support the launch of Ramses in April 2028, and the deadline to reach Apophis in February 2029, in time to meet the mission objectives. The rapidity of such a mission is a key success factor for a planetary defense strategy to react to a real hazard.
Ramses won’t be the only spacecraft headed to Apophis in 2029. After accomplishing its mission, NASA diverted the OSIRIS-REx spacecraft, now OSIRIS-APEX, to meet with Apophis. However, the encounter will only take place after the asteroid’s flyby with Earth, due to orbital mechanics limits.
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