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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - NEOShield-2 (Science and Technology for Near-Earth Object Impact Prevention)

Teaser

Summary

As a result of modern observing techniques thousands of near-Earth objects (NEOs) have been discovered over the past 20 years and the reality of the impact hazard has been laid bare. Even relatively small impactors can cause considerable damage: the asteroid that exploded over the Russian city of Chelyabinsk in February 2013 had a diameter of only 18 m yet produced a blast wave that damaged buildings and caused injuries to some 1500 people [Fig. 1]. The potentially devastating effects of an impact of a large asteroid or comet are now well recognized. Can we protect our civilisation from the next major impact?
In contrast to other natural disasters, such as earthquakes and tsunamis, the impact of an asteroid discovered early enough can be predicted and prevented. Following on from the original NEOShield project (FP7), the objectives of NEOShield-2 included improvement of the targeting accuracy and relative velocity of a kinetic impactor spacecraft to deflect a small asteroid, and development of autonomous spacecraft control systems to facilitate navigation close to a low-gravity, irregularly shaped asteroid. Scientific objectives included astronomical observations of NEOs and the analysis of archival data (radar, infrared, spectroscopy, etc.), complemented by modelling and computer simulations, to improve our understanding of their physical properties and how a NEO would respond to a deflection attempt (for a more detailed Executive Summary see: http://neoshield.eu/n2es).

Work performed

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 NEOTÏ‰IST [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.

Final results

Apart from the direct and tangible progress summarized above, we have demonstrated that a large international team of scientists and engineers, brought together by the FP7 and H2020 programmes, can work closely and effectively together to bring about significant advances in the complex and diverse fields relevant to the NEO impact threat. The efficiency of the team increased with time as the partners developed greater mutual understanding and respect. The results of our work and the nature of the impact hazard underline the need for resources to be made available in this field beyond the horizons of short-term project funding. The full socio-economic impact of our work cannot be realised unless the momentum built up since 2012 during the course of the NEOShield-2 and the original NEOShield projects is continued. The NEO impact hazard is a permanent problem, which can only be tackled by permanent effort.
Finally, the wider societal implications of our work lie in easing public concern over the impact hazard, and demonstrating that the scientific and space-engineering communities are abreast of the problem and have a good chance of successfully deflecting a dangerous NEO should one threaten the Earth in the near future.