The question of how to respond to warnings that a Near Earth Object (NEO) was on an eventual collision course with our home planet is a minor recurring theme here at WorldChanging. In a way, it's one of clearer issues that we grapple with -- there are no questions of human culpability or poor planning decisions to make the problem more complex. The reality is that our planetary neighborhood is pretty dangerous, and that one day, one of the thousands upon thousands of asteroids and comets swirling about our solar system is going to have Earth's name on it.
But it's something that, given enough warning, we could act to avert. We've written before of various calls for NASA to put together response plans, but haven't said anything about other space programs getting into the act. This was a mistake, as it appears that the ESA -- the European Space Agency -- is taking the issue of NEO impact very seriously, and is prepping the first in a series of missions to study what it would take to deflect an oncoming asteroid. The name of the mission is Don Quijote, and it will comprise two satellites working together: Hildalgo and Sancho (Jon first alerted us to plans for this mission back in July, 2004!).
This week, the ESA selected the two candidate asteroids for the Don Quijote mission. There are two major kinds of asteroids out there -- dark "carbonaceous" C-types, and bright "silicate" S-types. As Don Quijote will only be able to hit one target, the scientists have decided on compromise objects, combining features of both types. The two asteroids are 2002 AT4 and (10302) 1989 ML. The final target selection will be made just prior to Don Quijote's launch, in 2007.
The goals of Don Quijote are superficially similar to the recently-completed "Deep Impact" mission to the comet Tempel-1: slam an impactor probe (in this case, the "Hildago" satellite) into a Near Earth Object, then watch with a more distant observation satellite ("Sancho") for the result. The differences between the missions are substantial, however. The Deep Impact observer simply flew by its target comet; Sancho will orbit its mission target asteroid, and will launch a series of surface sensors and seismic probes to get a substantive level of detail about the effects of the impact on the object. In addition, Don Quijote will be the first probe devoted entirely to studying asteroid characteristics for later deflection efforts. In short, while the literary Don Quijote was famous for attacking windmills as imagined monsters, the ESA's Don Quijote may well be the first step in building a real defense against the very real threat of cosmic collision.
Beyond this, efforts such as Don Quijote have a direct value for all robotic space exploration. Research discussed this week from the UK's Engineering and Physical Sciences Research Council looks at the various ways in which figuring out how to deflect asteroids can improve overall satellite capabilities.
...a dangerous object is likely to be newly discovered and that means its orbit will be poorly known. "We'd probably have to launch a deflection mission without a clear idea of where we're aiming," says [EPSRC's] McInnes. So, the study will seek to find the best strategies for launching space missions into approximate intercept orbits that can be adjusted later.
To do this, it will investigate the additional fuel that such a spacecraft would require. Because fuel is heavy, spacecraft are traditionally designed to carry little extra. That will have to change with this new approach to space exploration.
Such seat-of-the-pants flying could result in more versatile spacecraft across the board. These would be better able to respond to a variety of unexpected situations. As well as fuel considerations, the team will investigate 'general purpose' orbits and flexible navigation strategies that keep a spacecraft's options open for longer, before committing it to a final destination.
The ESA's web pages on the Don Quijote mission and their overall NEO plans are interesting, but I want to draw particular attention to a document linked from the Don Quijote page. The 2003 Don Quijote Mission Executive Summary (PDF) provides a greater level of detail about the underlying science of the project, and has some fairly cool illustrations to boot. I'm particularly drawn to the mission orbit graphic, reproduced below, which has none of the overly-precise look of typical space mission maps:
Finally, as China preps its own advanced space program, it will be interesting to see if they begin to see a role for themselves in the global effort to protect against NEO impacts.
To me, this is fearsomely cool on so many levels: