NASA‘s OSIRIS-REx completed its last flyover from Bennu at around 6 a.m. EDT (4 a.m. MDT) on April 7 and is now slowly drifting away from the asteroid; however, the mission team will have to wait a few more days to find out how the spacecraft altered Bennu’s surface when it picked up a sample from the asteroid.
The OSIRIS-REx team added this flyby to document surface changes resulting from the Touch and Go (TAG) sample collection maneuver on October 20, 2020. “By examining the spread of excavated material around the TAG site, we will learn about the nature of the surface and subsurface materials along with the mechanical properties of the asteroid, ”says Dr. Dante Lauretta, principal investigator for OSIRIS-REx at the University of Arizona.
During the flyby, OSIRIS-REx imaged Bennu for 5.9 hours, covering more than one full rotation of the asteroid. It flew to the surface of Bennu within 3.5 kilometers – the closest since the TAG sample collection event.
It will take at least until April 13 for OSIRIS-REx to download all data and new photos of Bennu’s surface recorded during the flyby. It shares the Deep Space Network’s antennas with other missions such as Mars Perseverance and typically gets 4-6 hours of downlink time per day. “We collected approximately 4,000 megabytes of data during the flyby,” said Mike Moreau, OSIRIS-REx deputy project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Bennu is currently about 185 million miles from Earth, which means we can only achieve a downlink data rate of 412 kilobits per second, so it will take a few days to download all the flyby data.”
Once the mission team has received the images and other instrument data, they will study how OSIRIS-REx has scrambled Bennu’s surface. During landing, the spacecraft’s sampling head sank 1.6 feet (48.8 centimeters) into the surface of the asteroid and simultaneously fired a pressurized charge of nitrogen gas. The spacecraft’s thrusters kicked up a large amount of surface material during the back-away combustion, launching rocks and dust.
OSIRIS-REx With its pristine and precious asteroid payload, it will remain near Bennu until May 10, when it will fire its thrusters and begin its two-year cruise home. The mission will bring the asteroid monster to Earth on September 24, 2023.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides general mission management, systems engineering, and security and mission assurance for OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security – Regolith Explorer). Dante Lauretta of the University of Arizona, Tucson, is the lead investigator, and the University of Arizona also leads the mission’s science team and scientific observation planning and data processing. Lockheed Martin Space in Denver built the spacecraft and provides flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers program, operated by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the Scientific Mission Directorate in Washington.