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 mission team will continue to examine telemetry and tracking data over the next week to verify the new trajectory. 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.

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 Oct. 1 and Oct. 15 respectively, slowed the spacecraft by a total of approximately 1,088 mph (486 m/sec). AAM-3 and AAM-3A, which executed on Oct. 29 and Nov. 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 Nov. 30, the spacecraft will be on track to arrive at a position 12 miles (20 km) from Bennu on Dec. 3.