Original URL: http://www.theregister.co.uk/2011/05/26/asteroid_mission/

Roboprobe spacecraft off to grope asteroid

Possibly apocalyptic 'Yarkovsky effect' to be sussed

By Lester Haines

Posted in Science, 26th May 2011 11:30 GMT

NASA has announced it will send a roboprobe spacecraft to an asteroid to "pluck samples" from the near-Earth object and return them for perusal by ground-based boffins.

The improbably-named "Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer", known as OSIRIS-REx to its chums, will launch in 2016 ahead of a 2020 rendezvous with 1999 RQ36.

After six months of surface mapping, OSREx – as we at El Reg have decided to abbreviate it – will creep up on the 1,900ft diameter object* and extend a robotic arm to collect "more than two ounces" of material.

Artist's impression OSIRIS-REx collecting a sample from asteroid 1999 RQ36. Pic: NASA This sounds straightforward enough, but mission project scientist Dr Joseph Nuth notes: "Gravity on this asteroid is so weak, if you were on the surface, held your arm out straight and dropped a rock, it would take about half an hour for it to hit the ground. Pressure from the sun's radiation and the solar wind on the spacecraft and the solar panels is about 20 per cent of the gravitational attraction from RQ36. It will be more like docking than landing."

The collected samples will fall to Earth in 2023 in Utah's Test and Training Range, in a capsule similar to that used by the Stardust spacecraft to return samples of the comet Wild 2 in 2006.

NASA hopes 1999 RQ36 will offer insights into the formation of the solar system, as well as paving the way for future human deep-space forays. NASA head honcho Charles Bolden declared: "This is a critical step in meeting the objectives outlined by President Obama to extend our reach beyond low-Earth orbit and explore into deep space. It's robotic missions like these that will pave the way for future human space missions to an asteroid and other deep space destinations."

Jim Green, director of NASA's Planetary Science Division, chipped in with: "This asteroid is a time capsule from the birth of our solar system and ushers in a new era of planetary exploration. The knowledge from the mission also will help us to develop methods to better track the orbits of asteroids."

To help humanity "mitigate possible Earth impacts from celestial objects", OSREx will measure the "Yarkovsky effect" on 1999 RQ36. This is the "small push caused by the sun on an asteroid, as it absorbs sunlight and re-emits that energy as heat". NASA explains: "For scientists to predict an Earth-approaching asteroid's path, they must understand how the effect will change its orbit."

The $800m OSREx mission is the third in the New Frontiers Program. New Horizons headed off to Pluto and the Kuiper Belt in 2006, while Juno is set to launch in August this year for an extensive look at Jupiter. ®


*Which is "roughly the size of five football fields", as NASA correctly quantifies it.