Washington, Oct 3 (IANS): NASA's first mission to visit a near-Earth asteroid, the OSIRIS-REx, has executed the first of a series of exercises to slow down the spacecraft's speed to put it on course for its scheduled arrival at the asteroid Bennu in December.

The spacecraft's main engine thrusters fired in a braking manoeuvre designed to slow the spacecraft's speed relative to Bennu from approximately 491 metre/seconc to 140 metre/second, NASA said in a statement on Wednesday.

The mission team will continue to examine telemetry and tracking data as they become available and will have more information on the results of the first "Asteroid Approach Manoeuvre" (AAM-1) over the next week, the US space agency added.

During the next six weeks, the OSIRIS-REx spacecraft will continue executing the series of asteroid approach manoeuvres designed to fly the spacecraft through a precise corridor during its final slow approach to Bennu.

The last of these, AAM-4, scheduled for November 12, will adjust the spacecraft's trajectory to arrive at a position 20 km from Bennu on December 3.

After arrival, the spacecraft will initiate asteroid proximity operations by performing a series of fly-bys over Bennu's poles and equator, NASA said.

OSIRIS-REx, short for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, was launched on September 8, 2016.