While NASA's asteroid-capturing mission remains grounded from a lack of Congressional funding, a similar and equally ambitious ESA program is nearing fruition. In the coming months, the Rosetta spacecraft and its integrated Philae probe will become the first man-made objects to not only orbit an asteroid but land on it as well. Here's how they'll do it.
The European Space Agency began work on the Rosetta spacecraft in the early 1990s as part of the Horizon 2000 missions, and launched the spacecraft towards its target, 67P/Churyumov–Gerasimenko, in March of 2004 aboard an Ariane 5 rocket. For nearly a decade, the spacecraft has slowly wound its way to towards the asteroid but is expected to finally arrive in November of next year.
Once the Rosetta reaches 67P, it will spend an additional 17 months orbiting the asteroid. The Rosetta orbiter packs a dozen instruments including various infrared, ultraviolet, optical, and spectroscopic imaging systems as well as microwave and radar sounders and a variety of gas and particle analysers. These systems will allow the orbiter to study both the surface structure and core of the asteroid—as well as its chemical composition—before attempting the a risky landing manoeuvre with the Philae probe.
The Philae itself is a 220 kg carbon fibre landing craft designed to deploy from the Rosetta and fall towards the asteroid in a ballistic trajectory. Impact dampening legs and anchoring harpoons will ensure that the lander doesn't simply bounce off 67P and float off into the depths of space. If it does safely land on the asteroid, Philae's mission is expected to last between a week and a few months, as its array of nine sounders and particle analysers go about exploring 67P's internal structure.
It may not be as cool as NASA's plan to net a space rock with an autonomous robot and tow it home like a celestial deer strapped to the roof of a Buick, but the ESA's Rosetta mission will provide us with vital, and in some ways, basic knowledge about the untold numbers of asteroids that also inhabit our solar system. [ESA - Space - Wiki]