Near-Earth Object meeting has quite an impact
17 May 2000Representatives of ESA and many other European organisations gathered in Paris yesterday to discuss the threat from Near-Earth Objects (NEOs).
Non-ESA participants included the Secretary General of the International Astronomical Union, delegates from several ESA member states, experts from a number of astronomical observatories, including the European Southern Observatory, and a representative from the European Community.
The purpose of the meeting was to define a European strategy for the protection of the planet from Near-Earth Objects - asteroids and comets which pass close to the Earth's orbit.
"We were discussing with our European partners the best approach to tackle this threat and trying to identify the main 'actors' in this business," explained Marcello Coradini, ESA Coordinator of Solar System Missions. "This included discussions on coordination of efforts, possible future activities and their impact on the ESA budget."
At present, ESA studies NEOs as a by-product of investigations into space debris. The agency also supports the Spaceguard Foundation, which is located at the Institute of Astrophysics in Rome.
However, there are at least two future ESA space missions under study which could contribute to such studies. One of these, Gaia, is an ambitious astrometric mission to measure the positions of faint objects with a high degree of accuracy.
"Apart from measuring the positions of distant stars, Gaia will also be able to detect and locate small, fast-moving bodies such as NEOs no more than 500 metres across," said Dr. Coradini. "This is extremely important because impacts by objects of that size can wipe out a city the size of London."
A second possibility is offered by the BepiColombo mission to the innermost planet, Mercury. During its long trek through the inner Solar System, BepiColombo would have the opportunity to search for previously unknown asteroids and comets.
"Space missions such as these are essential if we are to discover the population of 'Inner NEOs' which lurk unseen between the Sun and Earth," said Dr. Coradini. "These are the most dangerous of all NEOs because they are hidden in the glare of the Sun and arrive without any warning."
"Space missions also allow us to make detailed spectral measurements, so that we can learn what they are made of," he went on. "This is much more difficult from the Earth."
However, ground-based follow-up observations are essential when trying to calculate the orbit of a newly found NEO. Without such observations, it is impossible to determine whether the object is likely to collide with the Earth. ESA could contribute to such observational programmes through the agency's one metre space debris telescope in the Canary Islands.
The meeting concluded that the best way forward is a two-phase approach. In Phase 1, there would be worldwide efforts to assess the magnitude of the NEO threat by compiling a complete catalogue of potential Earth impactors down to sub-kilometre scale.
Phase 2 would be to assess the impact on human society and to determine the best ways of reducing the severe consequences of an asteroid strike. Since schemes for asteroid destruction or deflection are still unproven and highly dangerous, civil protection efforts such as fall-out shelters or plans for mass evacuation may be the most appropriate in the short term.
"We would expect these two phases to be completed by 2010 - 2015," said Dr. Coradini.
"We should be safe until then!" he added.