RAMSES: Companion for Near-Earth Asteroid Apophis
When the asteroid Apophis grazes past Earth in April 2029, the space probe Ramses will be there to take scientific measurements. Ramses will accompany the asteroid for a total of six months.
On April 13, 2029, the asteroid Apophis will fly past Earth at a distance of just under 32,000 kilometers. Its flight path lies well within the Moon's orbit. A collision with Earth has now been ruled out with certainty. Nevertheless, such a close flyby of an asteroid is a once-in-a-millennium event. The European and Japanese space agencies are sending the Rapid Apophis Mission for Space Safety (RAMSES) space probe on a rendezvous course to study the flyby from a close distance.
RAMSES will arrive at Apophis approximately two months before its flyby of Earth and will accompany it for a total of six months. At times, the probe will venture as close as one kilometer to the asteroid.
The launch into space is planned for April 2028 (launch window: April 24th – May 11th, 2028). Equipped with eight scientific instruments, RAMSES will determine (among other properties) the composition, internal structure, surface, and porosity of the asteroid. In addition, the instruments will document with high temporal resolution how the asteroid, its shape, trajectory, and rotation change under the influence of Earth's gravity.
The MPS is sending the Ramses Plasma Spectrometer (RPS) along for the ride. It measures the energy and distribution of ions and electrons in the asteroid's environment.
Apophis is one of the asteroids that regularly crosses Earth's orbit. With a length of about 450 meters and a width of about 170 meters, it is of medium size. Numerous similar chunks are known to exist and regularly cross Earth's orbit on their way around the Sun. In order to protect our planet from impacts by such bodies in the future, it is crucial to know their properties as accurately as possible. In an emergency, this could help to develop a space mission to divert a threatening asteroid from its collision course with Earth.