The New Horizons spacecraft, which has now visited Pluto and the Kuiper belt, is not the only spacecraft to mark a major milestone on New Year’s Eve. NASA’s OSIRIS-REx set a new record as it entered near orbit around the asteroid Bennu. This marks the closest orbit of a spacecraft from Earth around such a small object in space.
NASA’s OSIRIS-REx embarked on its journey to Bennu in 2016 and reached it in December. The spacecraft surveyed the asteroid for a time as scientists calculated the best method to approach it and begin studying it up close. The asteroid Bennu is located 70 million miles from Earth. Scientists believe it’s important to study carbon-rich asteroids like it because they may have brought the building blocks of life to Earth millions of years ago.
NASA announced the important milestone in space exploration on New Year’s Eve, adding that it took only an eight-second burn on the spacecraft’s thrusters for it to enter close orbit. OSIRIS-REx set a new record because this is the closest any spacecraft has ever orbited its object of study in space. At only “5-millionths” the strength of Earth’s gravitational pull, Bennu’s gravity force is so small that it’s barely enough to sustain a stable orbit for the spacecraft.
NASA’s OSIRIS-REx probe is orbiting the asteroid Bennu just one mile from its center; the space agency describes the spacecraft’s orbit as occurring “at a snail’s pace.” It will take 62 hours for the probe to complete one orbit around the asteroid.
The close orbit will enable NASA’s OSIRIS-REx to capture detailed, accurate images which scientists will use to study the asteroid’s surface, which the space agency describes as a “rubble pile of primordial debris.” The spacecraft has already sent several images back to Earth. It also discovered signs of water in hydroxyl groups.
However, this is not where the mission ends; the space agency will need to make adjustments to the probe’s orbit to keep it stable. Those adjustments include so-called “’trim’ maneuvers,” which are used to counter the small forces between the two bodies so that the spacecraft can maintain its orbit.
If things go wrong and NASA’s OSIRIS-REx loses its balance while in orbit, it is programmed to fly away and avoid an accidental impact with the space rock. Then when the probe reaches a safe distance again, NASA’s team will try to put the spacecraft back into orbit.
After it set a new record, the spacecraft will go through multiple phases on its data- and image-collecting mission. After it completes all of its planned orbits and finishes gathering data, the spacecraft is expected to land on the asteroid briefly and collect a sample, which is scheduled to arrive back at Earth in a return capsule some time in September 2023.