Like ancient mariners and the Apollo astronauts, it needed the constancy of the constellations to navigate the dark unknown.
Bennu is thought to be a lump of rock from the earliest days of the Solar System.
The spacecraft will also carry a laser altimeter, a suite of cameras provided by the University of Arizona, spectrometers and lidar, which is similar to radar, using light instead of radio waves to measure distance.
He fidgeted in his chair, then stood.
For a sample-return mission, the asteroid has to be the right size. Osiris is the god of the afterlife, while Bennu represents the heron and creation. Scientists think it might be older than the Solar System itself, which is about 4.6 billion years ago.
OSIRIS-REx will spend the next 18 months there, surveying the landscape and probing Bennu's chemical makeup before finally selecting what piece of the asteroid it wants to bring back home.
OSIRIS-REx will return to Earth in September 2023, dropping the sample container off for a high-speed plunge to the Utah Test and Training Range about 80 miles west of Salt Lake City in Utah. The spacecraft will grab a sample and study the rock before coming home.
OSIRIS-REx has a camera suite, a laser altimeter for 3D mapping, a thermal emission spectrometer to take temperature and mineral content and spectrometers to measure X-rays, almost infrared and visible light. They may also uncover potentially useful natural resources such as organic molecules and precious metals.
Bennu is about 1,600 feet (500 meters) in diameter, about the size of a small mountain. OSIRIS-REx will actually need to spend a good deal of time hanging out in orbit around Bennu before it makes its move, so today is just confirmation of the probe's arrival.
To their delight, newly acquired close-ups of the asteroid closely match their predictions.
OSIRIS-REx and its instruments. Even the faint pressure of sunlight warming the spacecraft can create sufficient thrust to warp its orbit.
A fragment of the early solar system, Bennu is also considered potentially unsafe.
This ensures that the solar radiation pressure remains constant, so engineers can make sure they continuously counteract it.
Why Did NASA Send OSIRIS-REx to Bennu? TAGSAM is the heart of the spacecraft's mission. Video animations of the spacecraft's planned orbits look like an elaborate cosmic ballet.
The robotic explorer Osiris-Rex pulled within 12 miles (19 kilometers) of the diamond-shaped space rock.
If all goes well, the craft will bring the sample back to Earth in September 2023.
As NASA scientists learn more about Bennu, they'll be comparing their findings with counterparts from the Japanese Space Agency, whose Hayabusa 2 spacecraft arrived at the asteroid Ryugu earlier this year.
An arm mechanism called TAGSAM will reach out to collect the sample from Bennu's surface, making contact with the asteroid for five seconds in July 2020.
It was discovered in 1999, and scientists have been studying it ever since.
On Monday, the United States space agency's OSIRIS-REx spacecraft arrived at a nearby asteroid that's of great importance to scientists: it might have answers about what early Earth was like, but there's a decent chance it might hit us, too.