(CNN) NASA's OSIRIS-REx mission and the asteroid Bennu have had a date planned for two years, and just after noon ET today, they finally got to meet face to face. OSIRIS-REx fired its thrusters for a small burn, putting it about 4.3 miles from Bennu, marking the end of its journey to the asteroid.

The mission -- which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer -- is NASA's first asteroid sample return mission. It launched in September 2016 and will spend two years up close and personal with Bennu. First images of the asteroid from the spacecraft's perspective have appeared as it got closer and closer.

Bennu, as seen on approach by the OSIRIS-REx spacecraft.

On Tuesday, the spacecraft will fly within 5 miles of Bennu, which will help design future orbits and map the surface.

Over the next year, OSIRIS-REx will survey the asteroid using five scientific instruments on board the spacecraft. These instruments will help it determine a safe location from which to collect a small sample from Bennu's surface that will be returned to Earth in September 2023.

"Bennu's low gravity provides a unique challenge for the mission," said Rich Burns, OSIRIS-REx project manager at NASA's Goddard Space Flight Center. "At roughly 0.3 mile in diameter, Bennu will be the smallest object that any spacecraft has ever orbited."

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