RAMSES (Rapid Apophis Mission for Space Safety) is a joint mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), executed under ESA leadership. Its target is the asteroid (99942) Apophis, which will pass within 32000 km from Earth's surface on 13 April 2029. RAMSES is scheduled for launch in April 2028.
Discovered in 2004, Apophis orbits the Sun in about 323 days and, measuring 450 x 175 m, is roughly peanut-shaped. In April 2029, due to its proximity to Earth, Apophis will be visible to the naked eye under clear, dark skies over Europe and Africa. Recent calculations have ruled out the possibility that Apophis will strike Earth. Furthermore, this close flyby - similar to targeted spacecraft maneuvers - will raise the asteroid's orbit, thereby further reducing the risk of a collision for the next hundred years.
An object of this size comes this close to Earth only once every 5,000 to 10,000 years. This offers a unique opportunity to study objects of this kind. In addition, researchers will study the asteroid as Earth's gravity alters its physical properties. Their findings will help us protect our planet from similar objects that might be on a collision course in the future.
RAMSES will rendezvous with Apophis as it approaches Earth and will accompany the asteroid during its flyby to observe how it is deformed and altered by our planet's gravity.
Both the satellite and its instruments are based on the earlier HERA and Comet Interceptor missions. Since RAMSES was developed in record time, it was necessary to rely on existing components.
RAMSES carries five scientific instruments on board, as well as two CubeSats, one of which is scheduled to land on Apophis. The IWF is involved in CHANCES (Colour High-resolution Apophis Narrow-angle CamEra System), a camera system provided by the University of Bern. CHANCES is designed to capture high-resolution color images of the asteroid Apophis. The instrument has refocusing capabilities, enabling sharp images across a wide range of distances as well as a resolution of 1.5 cm from a distance of 1.2 km. Another component is the filter wheel, which features various color and polarization filters to characterize the mineralogical composition, surface texture, porosity, and terrain changes caused by tidal forces during the close flyby.
The IWF is contributing two filter sets, each combining a color bandpass filter with a defined polarization pattern. This enables the rapid characterization of large areas of the surface. Each filter consists of a blue (475 nm) or red (720 nm) bandpass filter. The differences in color intensity between the two filters are used to determine the surface texture. A polarizing layer is applied as a second layer to each filter. The effect of the surface on the polarization of light provides information about the surface's roughness and porosity.
To capture larger areas more quickly, the polarized layer is divided into circular zones, each with a different polarization direction. The individual camera images of the asteroid's surface overlap, but are located in different polarization zones. By comparing these individual areas, the surface texture can be determined more accurately and quickly.
