Orbital C Phase

Graphic of OSIRIS-REx in Orbital A

During Orbital C Phase, the OSIRIS-REx spacecraft entered its third orbital phase around asteroid Bennu. On August 8, 2019, the spacecraft performed a navigation maneuver that placed it into a circular orbit 1.1 miles (1.7 km) from the center of Bennu. While in this orbit, the spacecraft will take approximately 57 hours to complete one full orbit around the asteroid. In its previous orbital phase, Orbital B, the spacecraft was 0.4 miles (680 meters) above the asteroid’s surface, or 0.6 miles (930 meters) from the center of Bennu, and completed one orbit every 22 hours.

At a slightly higher altitude, Orbital C is similar to the frozen orbit used in Orbital A. The spacecraft will spend 5 weeks in this orbit, during which OSIRIS-REx will continue high cadence particle monitoring for 30 days. Using NavCam images, the team will further study the asteroid’s particle ejection events in order to pinpoint where the events are happening on Bennu, and to document the frequency of ejection events.

Orbital C is scheduled through the second week of September, after which the spacecraft will begin its transition into Reconnaissance A phase for high passes over the four candidate sample collection sites. Data from these passes will be used to select the final two sites – a primary and a back-up – for the touchdown event next year.