International defence against asteroids

The project was appropriately called NEOSHIELD (A global approach to near-Earth object (NEO) impact threat mitigation). This EU-funded initiative brought together an international group of scientists and engineers to investigate methods of defence against asteroids.

There are thousands of known NEOs, leading researchers to posit that a dangerous collision could occur as often as every few hundred years. However, it is possible to stop an asteroid from hitting Earth. The ultimate aim of the NEO Shield project was to develop a plan to knock a threatening massive asteroid out of its Earth-bound orbit.

One way to do this is to have a spacecraft impact the asteroid and impart enough force to change its orbit. The NEOSHIELD team evaluated a wide range of promising methods for deflecting NEOs, which may only mean providing a nudge in the right place at the right time.

The so-called kinetic impactor – a large space probe hits an asteroid at very high relative speed creating an impact sufficient to change its orbit – is feasible using today's technology for objects with diameters of less than one kilometre. But there were many unanswered questions concerning this method.

NEOSHIELD partners dealt with various aspects of the problem, from astronomical research into the physical properties of NEOs, and laboratory experiments and computer modelling to investigate how an asteroid would respond to a deflection attempt, to the development of technologies needed for a deflection mission. Specifically, they worked on ways to guide the spacecraft to the moving target at the right angle with the right velocity.

The most powerful but least appealing technique explored during the NEOSHIELD project relies on explosive power to divert or break up an Earth-bound asteroid. However, breaking up a large asteroid could be disastrous if it were to result in the Earth being showered with many large fragments.

The NEOSHIELD project provided detailed space-mission plans that could form the basis of a proposal to national and international space agencies for a mission to investigate or demonstrate NEO deflection techniques. International collaboration would be a prerequisite to the funding of such a mission, in addition to a global agreement on carrying out a defensive action in an emergency situation.