Probing the interior of asteroid APOPHIS, a unique opportunity in 2029

The near Earth asteroid (99942) Apophis, discovered in 2004, (with an approximately diameter of 270 meter) will come back very close to the Earth on April 13, 2029. During its 2029 pass, Apophis will present an unique opportunity for study its characterization and investigate possible mitigation techniques. The object will be easily visible from the Earth and it can be expected that its geometry and thermal properties will be well determined from ground based observations. However, the characterization of its interior will not be achievable from purely terrestrial observations. Such a characterization, beyond its high scientific value, is essential for planning any mitigation operation, should it be necessary in the future. Near Earth objects are a precious source of information as they represent a mixture of different population of small bodies containing fundamental issues on the origin and early evolution of the solar system. The accretion mechanism plays a major role in the formation of the planets of the solar system. These small bodies are believed in fact to be the remnants of the swarm of planetesimals from which the planets were formed. Monitoring the response of this asteroid to the gravitational constraints induced by its close approach to the Earth will permit to characterize its internal structure. A study to identify some affordable mission scenario for such a mission is presently underway at CNES (the French Space Agency). The paper will present the scientific and mitigation objectives of the mission as well as the preliminary results of the mission analysis and the main system characteristics.