NASA's OSIRIS-REx spacecraft will say farewell to asteroid Bennu and begin its journey back to Earth on May 10, the US space agency has said. During its October 20, 2020, sample collection event, the OSIRIS-REx spacecraft, short for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, collected a substantial amount of material from Bennu's surface, likely exceeding the mission's requirement of 60 grams.
The spacecraft is scheduled to deliver the sample to Earth on September 24, 2023.
"Leaving Bennu's vicinity in May puts us in the 'sweet spot,' when the departure maneuver will consume the least amount of the spacecraft's onboard fuel," Michael Moreau, OSIRIS-REx Deputy Project Manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said in a statement.
"Nevertheless, with over 593 miles per hour (265 meters per second) of velocity change, this will be the largest propulsive maneuver conducted by OSIRIS-REx since the approach to Bennu in October 2018."
The May departure also provides the OSIRIS-REx team with the opportunity to plan a final spacecraft flyby of Bennu.
This activity was not part of the original mission schedule, but the team is studying the feasibility of a final observation run of the asteroid to potentially learn how the spacecraft's contact with Bennu's surface altered the sample site.
If feasible, the flyby will take place in early April and will observe the sample site, named Nightingale, from a distance of approximately 3.2km, NASA said.
Bennu's surface was considerably disturbed after the Touch-and-Go (TAG) sample collection event, with the collector head sinking 48.8 centimetres into the asteroid's surface.
The spacecraft's thrusters also disturbed a substantial amount of surface material during the back-away burn.
The mission is planning a single flyby, mimicking one of the observation sequences conducted during the mission's Detailed Survey phase in 2019.
The spacecraft will remain in asteroid Bennu's vicinity until May 10, when the mission will enter its Earth Return Cruise phase.
As it approaches Earth, OSIRIS-REx will jettison the Sample Return Capsule (SRC).
The SRC will then travel through the Earth's atmosphere and land under parachutes at the Utah Test and Training Range.
Once recovered, NASA will transport the capsule to the curation facility at the agency's Johnson Space Center in Houston and distribute the sample to laboratories worldwide, enabling scientists to study the formation of our solar system and Earth as a habitable planet.