We have carried out detailed investigations of key technologies vital to the exploration and deflection of NEOs [Fig. 2], including autonomous guidance, navigation, and control systems for a spacecraft in the final approach and proximity phases to an asteroid for the purposes of in-situ science such as surface observations and setting down a lander module, and for a kinetic impactor spacecraft to maximize the targeting accuracy. A harmonized verification approach [Fig. 4] for those technology developments was established leading to an independent validation of all three scenarios to TRL 5-6 by extensive test campaigns. Furthermore, an innovative low-cost kinetic-impactor deflection demonstration concept called NEOTωIST [Fig. 3] has been developed. We have also demonstrated techniques for precise and rapid NEO orbit determination [Fig. 5] and developed mechanisms for the collection of material samples from the surface of a NEO [Fig. 6].
Astronomical observations [Fig. 7] of selected NEOs have been carried out for the purposes of broadening our knowledge of their mitigation-relevant physical properties, concentrating on the smaller sizes of most concern for mitigation purposes, and increasing the list of suitable candidate targets [Fig. 8 & 9] for deflection test missions. Statistical analyses of recently published NEO survey data have led to a novel means of estimating asteroid thermal inertia. Results suggest that the density and thermal conductivity of near-surface material increases rapidly with depth [Fig. 10], providing support for the kinetic impactor as a viable and effective deflection concept. Enhanced computer modelling and simulations in support of a NASA-ESA kinetic impactor study have provided insight into the post-impact ejecta evolution and fate [Fig. 11], which is crucial for the identification of safe locations for an observing spacecraft during and after a kinetic impactor deflection attempt.
Our study of the requirements for future research and international actions, in collaboration with the UN-mandated Space Mission Planning Advisory Group, has identified 11 areas requiring continued or increased effort at the present time. High on the priority list are the development and execution of deflection test missions on real asteroids and technologies for remotely-sensed physical characterization of small NEOs. Our results could form the basis of a European strategy for future mitigation-related endeavours.
