Two billion kilometres later, OSIRIS-Rex reaches Bennu


NASA’s mission completes half its two-way journey. Andrew Masterson reports.


Bennu, seen from OSIRIS-REx spacecraft from a distance of around 80 kilometres.

Bennu, seen from OSIRIS-REx spacecraft from a distance of around 80 kilometres. 

NASA/Goddard/University of Arizona

NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft is set to begin its preliminary survey of the asteroid Bennu, after finally completing its two billion kilometre journey to its target.

The craft, which launched in September 2016, reached the asteroid this week and is currently in a geo-stationary position 19 kilometres above its surface. Preparation for the arrival began in October, when the mission’s navigation team began a series of braking moves, slowing the craft down and refining its trajectory.

The next step in the mission begins on December 31, when OSIRIS-Rex descends to seven kilometres above Bennu and starts to orbit. It will collect data allowing the accurate mapping of its size, shape and spin.

By February, the craft will have moved even closer, dipping to just 1.25 kilometres above the surface, as it prepares for perhaps the most hazardous stage of the years-long journey – temporary touchdown.

Unlike most uncrewed craft launched by space agencies around the world, OSIRIS-Rex is on a two-way ticket. NASA intend to command it to collect about 60 grams of dirt and rocks from the asteroid’s surface, and then bring them back to Earth.

“As explorers, we at NASA have never shied away from the most extreme challenges in the solar system in our quest for knowledge,” says Lori Glaze, acting director for NASA’s Planetary Science Division.

“Now we’re at it again, working with our partners in the US and Canada to accomplish the Herculean task of bringing back to Earth a piece of the early solar system.”

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