The ISHTAR mission: Probing the interior of asteroids

ISHTAR (Internal Structure High-resolution Tomography by Asteroid Rendezvous) is a mission developed in response to ESA's recent call for ideas for Near Earth Object (NEO) exploration and discovery. The study, led by Astrium in cooperation with several scientific institutes throughout Europe, has produced a low-cost spacecraft design capable of performing multiple asteroid rendezvous and to characterize them with a focussed set of instruments. The ISHTAR concept is centred around a Radar Tomography payload .able to probe the internal structure of a small asteroid to depths of 300-1000m. This instrument uses low-frequency radio waves that can penetrate deep inside solid rock and records the reflected echoes caused by changes in the internal structure (permittivity). By combining these signals in a coherent fashion, it is possible to reconstruct a 3D image of the asteroid interior. The radar payload combined with a multispectral imager for measurement of the surface properties & surface geology, an IR spectrometer for mineralogical characterization, and a radio science experiment for accurate mass, mass distribution and density determination. The ISHTAR mission is designed to visit at least 2 NEOs, ideally one stony and one carbonaceous in composition, as these types are the most common among the NEO population. This unique combination of instruments and multiple rendezvous will allow the first detailed physical characterization of the NEO population and represents an essential step towards the development of mitigation strategies to protect the Earth from impact.