November 14, 2018 – NASA’s OSIRIS-REx spacecraft executed its fourth Asteroid Approach Maneuver (AAM-4) yesterday. 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). The ACS thrusters are capable of velocity changes as small as 0.02 mph (0.01 m/sec). The maneuver targeted the spacecraft to fly through a corridor designed for the collection of high-resolution images that will be used to build a shape model of Bennu. The mission team will continue to examine telemetry and tracking data over the next week to verify the new trajectory.
With the execution of AAM-4, the OSIRIS-REx spacecraft concludes a six-week series of Bennu approach maneuvers. AAM-1 and AAM-2, which executed on October 1 and October 15 respectively, slowed the spacecraft by a total of approximately 1,088 mph (486 m/sec). AAM-3 and AAM-3A, which executed on October 29 and November 5 respectively, further refined the spacecraft’s trajectory and speed to set the conditions for a successful AAM-4 maneuver.
After a final correction maneuver scheduled for November 30, the spacecraft will be on track to arrive at a position 12 miles (20 km) from Bennu on December 3.
According to a Twitter post from OSIRIS-REx Principal Investigator Dante Lauretta, the spacecraft will deploy its Touch-and-Go Sample Acquisition Mechanism (TAGSAM) today. TAGSAM is the robotic arm that will be used to retrieve a pristine sample of asteroid Bennu to be returned to Earth in 2023. Today will be the first time that the team has exercised the full range of motion on TAGSAM since launch.