Washington, Apr 2 (IANS): NASA's OSIRIS-REx spacecraft will get one last close encounter with Bennu on April 7 as it performs a final flyover to capture images of the asteroid's surface.

While performing the flyover, the spacecraft will observe Bennu from a distance of about 3.7 km - the closest it jhas been since the Touch-and-Go Sample Collection event on October 20, 2020, NASA said on Thursday.

The OSIRIS-REx team decided to add this last flyover after Bennu's surface was significantly disturbed by the sample collection event.

During touchdown, the spacecraft's sampling head sunk 48.8 centimetres into the asteroid's surface and simultaneously fired a pressurised charge of nitrogen gas.

The spacecraft's thrusters also mobilised a substantial amount of surface material during the back-away burn.

Because Bennu's gravity is so weak, these various forces from the spacecraft had a dramatic effect on the sample site -- launching many of the region's rocks and a lot of dust in the process.

This final flyby of Bennu will provide the mission team an opportunity to learn how the spacecraft's contact with Bennu's surface altered the sample site and the region surrounding it.

After the Bennu flyby, it will take several days for the data from the flyover to be downlinked to Earth.

Once the data are downlinked, the team will inspect the images to understand how OSIRIS-REx disturbed the asteroid's surface material.

At this point, the team will also be able to evaluate the performance of the science instruments.

The spacecraft will remain in asteroid Bennu's vicinity until May 10, when the mission will enter its Return Cruise phase and begin its two-year journey back to Earth.

As it approaches Earth, the spacecraft will jettison the Sample Return Capsule (SRC) that contains the rocks and dust collected from Bennu.

The SRC will then travel through the Earth's atmosphere and land under parachutes at the Utah Test and Training Range on September 24, 2023.

Once recovered, the capsule will be transported to the curation facility at the agency's Johnson Space Center in Houston, where the sample will be removed for distribution to laboratories worldwide, enabling scientists to study the formation of our solar system and Earth as a habitable planet, NASA said.