Of the six studies, three were space-based observatories for detecting NEOs and three were rendezvous missions. All addressed the growing realisation of the threat posed by Near-Earth Objects (NEOs) and proposed ways of detecting NEOs or discovering more about them from a close distance.

A panel of six experts, known as the Near-Earth Object Mission Advisory Panel (NEOMAP) assessed the proposals. Alan Harris, German Aerospace Centre (DLR), Berlin, and Chairman of NEOMAP, says, “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.”

As a result, the panel decided that ESA should leave detection to ground-based telescopes for the time being, until the share of the remaining population not visible from the ground becomes better known. The need for a space-based observatory will then be re-assessed. The panel placed its highest priority on rendezvous missions, and in particular, the Don Quijote mission concept. “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,” explains Harris.

The Don Quijote mission concept will do this by using two spacecraft, Sancho and Hidalgo. Both are launched at the same time but Sancho takes a faster route. When it arrives at the target asteroid it will begin a seven-month campaign of observation and physical characterisation during which it will land penetrators and seismometers on the asteroid’s surface to understand its internal structure.

Sancho will then watch as Hidalgo arrives and smashes into the asteroid at very high speed. This will provide information about the behaviour of the internal structure of the asteroid during an impact event as well as excavating some of the interior for Sancho to observe. After the impact, Sancho and telescopes from Earth will monitor the asteroid to see how its orbit and rotation have been affected.

Harris says, “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.”

On 9 July, the findings were presented to the scientific and industrial community. Representatives of other national space agencies were also invited in the hope that they will be interested in developing a joint mission, based around this concept.

Andrés Galvez, ESA’s Advanced Concepts Team and technical officer for the NEOMAP report says, “This report gives us a solid foundation to define programmatic priorities and an implementation strategy, in which I also hope we are joined by international partners”.

With international cooperation, a mission could be launched as early as 2010-2015.

Note for editors:

The six mission concepts studied were:

• Earthguard-1 – a small space telescope for NEO discovery, especially the Atens and “inner-Earth objects” (IEOs) that are difficult to detect from the ground.
• European Near-Earth Object Survey (EUNEOS) – a space telescope for NEO discovery
• NEO Remote Observations (NERO) – an optical/infrared space telescope for NEO discovery and physical characterisation.
• Smallsat Intercept Missions to Objects Near Earth (SIMONE) – a flotilla of low-cost microsatellites for near-Earth asteroid rendezvous and in-situ remote sensing
• Internal Structure High-resolution Tomography by Asteroid Rendezvous (ISHTAR) – uses radar tomography for an in-situ study of internal structure
• Don Quijote – uses explosive charges, an impactor, seismic detectors and accelerometers for an in-situ study of internal structure and momentum transfer

The Don Quijote study was performed by staff from: DEIMOS (Prime Contractor), ASTRIUM GmbH, University of Pisa, SpaceGuard Foundation, IPGP and the University of Bern.