Orbital B Phase

During Orbital B Phase, the OSIRIS-REx spacecraft entered its second orbital phase around asteroid Bennu. On June 12, 2019, the spacecraft performed a navigation maneuver that placed it into a circular orbit 0.4 miles (680 meters) above the asteroid’s surface, or 0.6 miles (930 meters) from the center of Bennu. This orbit will break the record that OSIRIS-REx set during Orbital A phase for the closest a spacecraft has ever orbited a small planetary body—which was approximately 0.8 miles (1.3 km) above the surface. During this phase, the spacecraft is traveling 0.16 mph (7 cm/sec), with each orbit lsting about 22 hours.

The first two weeks of Orbital B will be spent investigating the causes of Bennu’s particle ejection events by taking frequent images of the asteroid’s horizon. The remaining five weeks of Orbital B will focus on mapping the asteroid from a close range. The OSIRIS-REx Laser Altimeter (OLA) will produce a full terrain map; PolyCam will form a high-resolution, global image mosaic; and the OSIRIS-REx Thermal Emission Spectrometer (OTES) and the REgolith X-ray Imaging Spectrometer (REXIS) will produce global maps in the infrared and X-ray bands. The team will use the data from Orbital B to select four sample sites to be thoroughly evaluated during the Reconnaissance Phase of the mission.

Orbital B is scheduled through the second week of August, after which the spacecraft will enter Orbital C Phase and transition to a slightly higher altitude for additional particle observations.