On New Yr’s Eve, whereas many scientists, engineers and area fans centered on NASA’s New Horizons probe because it raced towards Ultima Thule within the distant Kuiper Belt, one other group of flight controllers was finishing up its personal record-breaking manoeuvre nearer to dwelling: guiding the OSIRIS-REx spacecraft into orbit round a tiny asteroid named Bennu.
At 7:43 UTC on 31 December, 112 million kilometres (70 million miles) from Earth, OSIRIS-REx executed an eight-second thruster firing that allowed the spacecraft to be captured by Bennu’s minuscule gravity, simply 5 millionths as sturdy as Earth’s. The ensuing 62-hour orbit carries the spacecraft inside 1.75 kilometres (about 1 mile) of the asteroid’s centre.
Bennu is the smallest physique ever orbited by a spacecraft. It resembles a considerably tetrahedron-shaped rubble pile measuring about 510 metres (1,673 ft) throughout from pole to pole. For comparability, there are at present 9 skyscrapers world wide which are taller than the asteroid’s polar width.
The $1 billion OSIRIS-REx mission was launched in September 2016 and reached reached Bennu’s speedy neighborhood on three December. After exhaustive observations from orbit later this 12 months, the spacecraft will transfer in to the touch the asteroid’s floor in the summertime of 2020, utilizing a tool on the tip of its robotic arm to collet soil and rock samples for return to Earth.
Despite the fact that OSIRIS-REx is now in orbit, Bennu’s gravitational pull is so tenuous further thruster firings might be required to take care of the spacecraft’s trajectory and counteract photo voltaic radiation and thermal strain from the asteroid’s floor that in any other case would push it off track.
“Our orbit design is extremely depending on Bennu’s bodily properties, comparable to its mass and gravity subject, which we didn’t know earlier than we arrived,” mentioned Mike Moreau, OSIRIS-REx’s flight dynamics system supervisor at NASA’s Goddard Area Flight Heart.
“Up till now, we needed to account for all kinds of attainable situations in our pc simulations to verify we may safely navigate the spacecraft so near Bennu. Because the group discovered extra in regards to the asteroid, we included new data to hone in on the ultimate orbit design.”
Beginning in February, OSIRIS-REx will perform a sequence of shut flybys of Bennu to take high-resolution pictures of the asteroid’s floor to assist scientists choose a pattern assortment web site. Then, in the summertime of 2020, the spacecraft will briefly contact the floor of Bennu to retrieve a pattern that might be returned to Earth in September 2023.
Getting OSIRIS-REx safely into orbit “continued our lengthy string of successes,” mentioned Dante Lauretta, the mission’s principal investigator on the College of Arizona. “With the navigation marketing campaign coming to an finish, we’re trying ahead to the scientific mapping and pattern web site choice section of the mission.”