Osiris, Ramses spacecraft to study asteroid Apophis
The Asteroid Apophis, named after a enormous serpent representing chaos and evil from Egyptian mythology, is scheduled for a close encounter with the Earth in April 2029. The asteroid will be studied by a pair of spacecraft from NASA and ESA, Osiris and Ramses. Osiris is the Egyptian god of the underworld, resurrection and fertility, while Ramses refers to a series of ancient pharoahs, also known as Ramesses.
On 19 June, 2004, astronomers at the Kitt Peak National Observatory in Arizona, USA noticed a spot of light moving through the constellation of Pisces. This was an asteroid, initially designated as 2024 MN4, and dubbed 99942 Apophis after follow-up observations confirmed the object. The initial observations indicated that the asteroid will impact the Earth in 2029, which is why it was named after an Egyptian serpent deity representing chaos, darkness, evil and destruction. The asteroid is both a Near Earth Object (NEO), with an orbit that crosses that of the Earth and a Potentially Hazardous Asteroid (PHA), a large asteroid that can strike the Earth in the distant future.
Follow-up observations by optical telescopes and radar instruments allowed scientists to finetune the trajectory, and determine that the asteroid will not be striking the Earth in 2029 after all. Instead, it will approach within 31,600 kilometers, closer than geostationary satellites. The asteroid measures 370 metres across and such a close approach by an asteroid of similar size takes place only every 5,000 to 10,000 years. During the close encounter, the asteroid will be visible to the naked eye from Asia, Africa and Europe. The flyby will take place on 13 April, 2029.
NASA’s OSIRIS-APEX mission to study Asteroid Apophis
In 2023, NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer) mission successfully lobbed a capsule containing samples retrieved from the asteroid Bennu towards the Earth, following a seven year mission. Subsequently, NASA repurposed the spacecraft and extended its mission, taking advantage of the 2029 close encounter with asteroid Apophis. The spacecraft is now dubbed OSIRIS-APEX. Launched in 2016, OSIRIS-REx completed its primary mission with more than a quarter of its fuel remaining, which is why NASA opted to use it to study Apophis.
Illustration of Apophis during its close approach to Earth. (Image Credit: NASA).
OSIRIS-APEX will only be able to reach asteroid Apophis shortly after the flyby, arriving on 21 April, 2029. The mission will spend 18 months in orbit around the asteroid, and will investigate how the close encounter with the Earth alters the orbit, spin and surface of the asteroid. The gravitational influence of the Earth is expected to trigger quakes or landslides on Apophis. NASA plans to use an innovative approach to study the deeper, subsurface material, by using the thrusters on the spacecraft to blow away the upper layers. The approach allows for spectral analysis of the composition of the asteroid.
Asteroid Apophis is primarily made up of silicates, nickel and iron. The observations by the OSIRIS-APEX mission will allow scientists to better understand S-type asteroids, which are the most common potentially hazardous asteroids. The research is expected to inform planetary defence strategies, which is the endeavour to protect the planet from potential impactors. Unlike the Bennu mission, the OSIRIS-REx spacecraft will not be collecting any samples, but will rely on remote sensing and surface interaction to maximise the science returns from the payloads on board. The extended mission costs $200 million on top of the $800 million cost of OSIRIS-REX, but benefits from using repurposed hardware. The observations will provide a rare opportunity to observe the effects of tidal forces on a large asteroid, from up-close.
ESA’s Ramses mission to asteroid Apophis
The European Space Agency has mounted its own mission to study Asteroid Apophis, called the Rapid Apophis Mission for Space Safety (RAMSES). Unlike the OSIRIS-APEX spacecraft, Ramses will arrive earlier, rendezvousing with Apophis in February 2029, about two months before the scheduled flyby. The timing allows Ramses to observe the asteroid before, during and after the close encounter, providing a comprehensive before and after perspective. Full funding for the mission is yet to be approved, with ESA aiming for a launch in April 2028.
Ramses will orbit Apophis, mapping its surface, and will deploy a pair of CubeSats. One will be used for remote observations, while the other will land on the surface and offer ground-level data. This CubeSat will be on the surface, using low-frequency radar and a gravimeter to measure how the shape,rotation and internal structure of Apophis changes during the close encounter. The tidal forces are expected to squeeze Apophis, potentially revealing new material. This data is crucial for understanding how large, stony asteroids react to gravitational stress, enhancing the deflection strategies against future threats.
The observations by NASA’s OSIRIS-APEX spacecraft and ESA’s Ramses mission are expected to be complementary to each other. ESA is racing against a tight timeline to capitalise on the rare encounter. ISRO may dispatch a payload to Apophis on the Ramses mission. In April 2029, an asteroid and two spacecraft named after Egyption gods will meet in the sky, Apophis, Ramses and Osiris.