The spacecraft will enter orbit around Bennu on December 31 -thus making Bennu, which is only about 1,600 feet (492 meters) across - or about the length of five football fields - the smallest object ever orbited by a spacecraft.
"During our approach toward Bennu, we have taken observations at much higher resolution than were available from Earth", said Rich Burns, the project manager of OSIRIS-REx at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Today, scientists burned the engines to place OSIRIS-REx safely in its orbit around Bennu, 7 kilometres from the asteroid at closest approach.
NASA's first-ever mission created to visit an asteroid and return a sample of its dust back to Earth arrives Monday at its destination, Bennu, two years after launching from Cape Canaveral, Florida. A mission program will precede the event at 11:15 a.m. EST (1615 GMT). That sample, assuming everything goes according to plan, will be returned to researchers on Earth in 2023.
Both Bennu and Ryugu are near-earth asteroid, with a diameter of about 500 meters and 900 meters respectively. During this period, OSIRIS-REx completed four maneuvers slowing the spacecraft's velocity from approximately 1,100 miles per hour (491 m/sec) to 0.10 miles per hour (0.04 m/sec) relative to Bennu, which resulted in the slower approach speed at the end of the video. The spacecraft will also carefully collect a sample of the asteroid.
The Touch-and-Go Sample Acquisition Mechanism (TAGSAM) will suck up the regolith, kicked up by its nitrogen gas thrusters, and hopefully collect enough to study back at home. The agency's most exhaustive visit was made by the Dawn spacecraft, which ended its mission earlier this year. The spacecraft executed a maneuver that transitioned it from flying toward Bennu to operating around the asteroid.
The sample container will then break free from Osirus Rex and head towards Earth in 2021, parachuting down to Utah. The asteroid has an orbit that brings it relatively close to Earth about once every six years.More news: Joshua calls out ‘fool’ Wilder and Fury
It is the first USA attempt to gather asteroid samples for return to Earth, something only Japan has accomplished so far. It will first survey the asteroid's surface for a year, before selecting a safe and "scientifically interesting' location to scoop up some rocks.
But while the spacecraft might tell us some things about where we have been and where we are headed, it also can remind us of where we are right now", NASA officials said in a statement.
"It's been a long time coming for the arrival, and we're really looking forward to the next chapter of this mission", Heather Enos, the OSIRIS-REx deputy principal investigator from the University of Arizona, said in a NASA press video.
A fragment of the early solar system, Bennu is also considered potentially risky.
"When we understand Bennu, we will understand something fundamental about our solar system". Bennu may contain the molecular precursors to the origin of life and the Earth's oceans.