ESA opts for intervention over observation in tackling dangerous asteroids

Brussels, 15 Jul 2004

After considering six different mission studies, all aimed at increasing understanding of potentially dangerous near Earth objects (NEOs), the European Space Agency (ESA) has decided to develop a mission to actually move an asteroid.

Of the six missions under consideration, three were space-based observatories for detecting NEOs, while the others proposed rendezvous scenarios. The decision to develop one of the later options was taken in light of recent advances in Earth-based observation of asteroids, according to ESA.

The recommendation was made by an expert NEO advisory panel, chaired by Alan Harris of the German Aerospace Centre. Dr Harris said: 'The task has been very difficult because the goalposts have changed. When the studies were commissioned, the discovery business was in no way as advanced as it is now. Today, a number of organisations are building large telescopes on Earth that promise to find a very large percentage of the NEO population at even smaller sizes than visible today.'

Therefore, the advisory panel decided to leave detection to ground-based telescopes for the time being and instead place priority on contact missions. The final choice was the Don Quijote mission, which proposes sending two spacecraft, Hidalgo and Sancho, to rendezvous with an NEO.

'If you think about the chain of events between detecting a hazardous object and doing something about it, there is one area in which we have no experience at all and that is in directly interacting with an asteroid, trying to alter its orbit,' explained Dr Harris.

Under the Don Quijote mission scenario, both spacecraft are launched towards an asteroid at the same time, but by taking a faster route, Sancho will arrive some seven months before Hidalgo. Sancho would then send penetrators and seismometers to the asteroid's surface to begin observing and characterising its internal structure.

Sancho will continue to observe as Hidalgo arrives, and slams into the asteroid at extreme high speed. This not only allows Sancho to collect information about the behaviour of the internal structure of the object during an impact, but also excavates some of the interior for further analysis. Following the collision, Sancho and telescopes on Earth will assess how the object's orbit and rotation have been affected.

Dr Harris explains: 'When we do actually find a hazardous asteroid, you could imagine a Don Quijote-type mission as a precursor to a mitigation mission. It will tell us how the target responds to an impact and will help us to develop a much more effective mitigation mission.'

The recommendations of the NEO advisory panel have been presented to representatives of other national space agencies in the hope that a joint mission could be developed around the Don Quijote concept. With such international cooperation, ESA believes that the mission could be launched within a decade.
For further information, please consult the following web address:
http:///www.esa.int/gsp/NEO/

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