20 Days To Bennu: NASA’s OSIRIS-REx Spacecraft Performs Final Asteroid Approach Maneuver

After chasing the asteroid for two years, OSIRIS-REx will finally catch up to Bennu at the beginning of December.

Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its Attitude Control System (ACS) thrusters.
NASA/University of Arizona

After chasing the asteroid for two years, OSIRIS-REx will finally catch up to Bennu at the beginning of December.

NASA’s first asteroid sampling mission, the OSIRIS-REx, is just 20 days away from reaching its destination. On November 12, the spacecraft executed its fourth and final Asteroid Approach Maneuver ahead of arrival at Bennu — a 1,640-foot-wide space rock floating 54 million miles away from Earth.

Dubbed AAM-4, the maneuver allowed the space probe to reduce its speed relative to Bennu and set the OSIRIS-REx mission on course for the highly-anticipated rendezvous with the asteroid on December 3.

“The spacecraft fired its Attitude Control System (ACS) thrusters to slow the spacecraft from approximately 0.31 mph (0.14 m/sec) to 0.10 mph (0.04 m/sec),” NASA announced yesterday.

According to the space agency, the probe’s ACS thrusters are capable of exerting velocity changes as small as 0.02 mph (0.01 m/sec).

“I’ll be relying on them a lot when I start flying around Bennu,” the OSIRIS-REx team tweeted yesterday.

This is the last of a series of four maneuvers that began on October 1 and served to progressively slow down the spacecraft in preparation for the big day. So far, these scheduled engine burns have served to reduce the spacecraft’s cruising speed by more than 1,088 mph (486 m/sec).

At the start of these procedures, OSIRIS-REx was traveling toward Bennu at a speed of about 1,100 mph (491 m/sec). The AAM-1 maneuver, conducted on October 1, reduced the probe’s speed to 313 mph (140 m/sec), as the Inquisitr previously reported.

Artist concept of NASA's OSIRIS-REx spacecraft arriving at asteroid Bennu.
Artist’s concept of NASA’s OSIRIS-REx spacecraft arriving at asteroid Bennu. NASA's Goddard Space Flight Center

The following two maneuvers — AAM-2 and AAM-3, executed on October 15 and October 29, respectively — “further refined the spacecraft’s trajectory and speed to set the conditions for a successful AAM-4 maneuver,” explained NASA.

As NASA points out, the OSIRIS-REx team at mission control will be keeping a close eye on the spacecraft’s telemetry, tracking the AAM-4 data over the next week to verify the new trajectory.

Next up for OSIRIS-REx is a final correction maneuver slated to take place on November 30. Following this procedure, the spacecraft will be on track to arrive at a position 12 miles (20 kilometers) from Bennu on December 3.

One great thing about these AAM maneuvers — aside from getting us closer and closer to this fascinating asteroid — is that they were designed to enable the OSIRIS-REx spacecraft to fly through a precise corridor ahead of its final slow approach to Bennu.

This specific trajectory allows the probe to collect high-resolution images of the asteroid — as was the case during AAM-3, the Inquisitr recently reported. At the time, the OSIRIS-REx snapped its first “super-resolution” photo of Bennu, taken from about 205 miles (330 kilometers) from the surface of the asteroid.

On November 2, the spacecraft acquired another set of images that showed the full rotation of the asteroid. These photos were captured from a distance of approximately 122 miles (197 km) away and allowed the team to see Bennu from all sides, NASA reported last week.

All these data will ultimately be used to build a shape model of Bennu so we can understand more about its surface before the OSIRIS-REx swoops down on the asteroid to grab a dust and rock sample in early July 2020.