Ramses Plasma Spectrometer (RPS)
The instrument is the first plasma spectrometer with high particle energy resolution and high time resolution to be used in an asteroid mission.
RPS measures the energy and distribution of ions and electrons in the asteroid's environment.
The unique near-Earth trajectory of asteroid Apophis allows RPS to study the asteroid's interaction with both the solar wind and the particles of Earth’s radiation belt. This is because the asteroid Apophis will fly so close to Earth that it will even penetrate the outer radiation belt. Captured by Earth's magnetic field, high-energy particles race around our planet there.
In addition, RPS can help determine the surface composition of the asteroid.
RPS aims to answer three scientific questions.
- How does asteroid Apophis interact with the plasma environment surrounding it? At the beginning and end of the mission, the focus will be on its interaction with the solar wind. During its flyby of Earth, the interaction with the Earth's radiation belts will be crucial.
- Which plasma physics processes determine the environment near the surface of Apophis? On its journey through space, the asteroid is constantly bombarded by particles from the solar wind or radiation belts. This bombardment can catapult ions and electrons from the asteroid's surface into space in various ways (sputtering, backscattering, emission of Auger and secondary electrons). RPS will investigate these processes in detail.
- What elements make up the surface of Apophis? Auger electrons and sputtered ions make it possible to determine the composition of the asteroid's surface.
RPS offers high energy and temporal resolution for these investigations.
RPS is an almost identical twin of the instrument PEP-JEI, which is currently traveling to Jupiter's icy moons aboard ESA's JUICE spacecraft. Such “reuse” is possible because the conditions in the plasma environment of Jupiter's large moons are similar to those near Earth. Necessary changes and adjustments are currently being made in collaboration with the Swedish Institute of Space Physics IRF.