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On December 31, NASA’s OSIRIS-REx aircraft entered into apogee about the asteroid Bennu, and fabricated Bennu the aboriginal article anytime to be orbited by a spacecraft.
At 2:43 p.m. EST on December 31, while abounding on Earth able to acceptable the New Year, NASA’s OSIRIS-REx spacecraft, 70 actor afar (110 actor kilometers) away, agitated out a single, eight-second bake of its thrusters – and bankrupt a amplitude analysis record. The aircraft entered into apogee about the asteroid Bennu, and fabricated Bennu the aboriginal article anytime to be orbited by a spacecraft.
“The aggregation connected our continued cord of successes by active the orbit-insertion action perfectly,” said Dante Lauretta, OSIRIS-REx arch investigator at the University of Arizona, Tucson. “With the aeronautics attack advancing to an end, we are attractive advanced to the accurate mapping and sample armpit alternative appearance of the mission.”
Lauretta, forth with his team, spent the aftermost day of 2018 with his anxiety buried on Earth, but his apperception focused on space. “Entering apogee about Bennu is an amazing ability that our aggregation has been planning for years,” Lauretta said.
The force of Bennu is so small, armament like solar radiation and thermal burden from Bennu’s apparent become abundant added accordant and can advance the aircraft about in its apogee abundant added than if it were orbiting about Earth or Mars, area force is by far the best ascendant force.- Dan Wibben, OSIRIS-REx Action and Aisle Architecture Lead
Inching about the asteroid at a snail’s pace, OSIRIS-REx’s aboriginal apogee marks a bound for humankind. Never afore has a aircraft from Earth circled so abutting to such a baby amplitude article – one with almost abundant force to accumulate a agent in a abiding orbit.
Now, the aircraft will amphitheater Bennu about a mile (1.75 kilometers) from its center, afterpiece than any added aircraft has appear to its angelic article of study. (Previously the abutting apogee of a all-embracing anatomy was in May 2016, aback the Rosetta aircraft orbited about four afar (seven kilometers) from the centermost of the comet 67P/Churyumov-Gerasimenko.) The adequate ambit is all-important to accumulate the aircraft bound to Bennu, which has a force force alone 5-millionths as able as Earth’s. The aircraft is appointed to apogee Bennu through mid-February at a comfortable 62 hours per orbit.
Now that the OSIRIS-REx aircraft is afterpiece to Bennu, concrete capacity about the asteroid will bound into bluff focus, and the spacecraft’s bout of this bits accumulation of basic bits will become added abundant and focused.
“Our apogee architecture is awful abased on Bennu’s concrete properties, such as its accumulation and force field, which we didn’t apperceive afore we arrived,” said OSIRIS-REx’s flight dynamics arrangement administrator Mike Moreau, who is based at NASA’s Goddard Amplitude Flight Centermost in Greenbelt, Maryland.
“Up until now, we had to annual for a advanced array of accessible scenarios in our computer simulations to accomplish abiding we could cautiously cross the aircraft so abutting to Bennu. As the aggregation abstruse added about the asteroid, we congenital new advice to hone in on the final apogee design,” he said.
The simulations accept played a analytical role. The OSIRIS-REx mission, afterwards all, was advised based on circuitous computer programs that predicted — absolutely accurately, as it turns out — the backdrop of Bennu and how the spacecraft’s aisle would behave. This active alertness accustomed the aggregation to cross the agent cautiously to Bennu in December and put some questions to blow (there are, indeed, signs of age-old baptize preserved in Bennu’s rocks) and to fly over its poles and equator in a basic analysis that led to some surprises (Bennu has abounding ample boulders).
Having completed the basic analysis of Bennu with a flyby of its south pole on December 16, the aircraft confused to a safe 31 afar (50 kilometers) abroad from the asteroid to accord the aeronautics aggregation a adventitious to regroup and adapt for apogee insertion. Next, Lockheed Martin engineers programmed the aircraft to activate affective aback to a position about nine afar (15 kilometers) over Bennu’s arctic pole to adapt for three burns of its thrusters over the advance of 10 canicule that would abode the aircraft into orbit.
Even admitting OSIRIS-REx is in the best abiding apogee possible, Bennu’s gravitational cull is so aerial that befitting the aircraft safe will crave casual adjustments, said Dan Wibben, OSIRIS-REx action and aisle architecture advance at KinetX Aerospace in Simi Valley, California.
“The force of Bennu is so small, armament like solar radiation and thermal burden from Bennu’s apparent become abundant added accordant and can advance the aircraft about in its apogee abundant added than if it were orbiting about Earth or Mars, area force is by far the best ascendant force,” he said.
The OSIRIS-REx aeronautics aggregation will use “trim” assignment to hardly advance the aircraft in one administration or addition to actual its apogee and adverse these baby forces. If the aircraft drifts abroad from Bennu, or some added botheration armament it into safe mode, it has been programmed to fly abroad from the asteroid to break safe from impact.
“It’s simple logic: consistently bake against the Sun if article goes wrong,” said Coralie Adam, OSIRIS-REx advance optical aeronautics architect at KinetX. Engineers can cross the aircraft aback into apogee if it drifts away, Adam said, admitting that’s absurd to happen.
This alternation of images were taken over the advance of about four hours and 19 account on Dec. 4, 2018, as OSIRIS-REx fabricated its aboriginal canyon over Bennu’s arctic pole. Credit: NASA/Goddard/University of Arizona
The aeronautics and aircraft operations teams are focused on the aboriginal alternate phase. Their primary ambition is to alteration abroad from star-based navigation, which accustomed the aggregation to locate the aircraft based on pictures of the brilliant formations about it taken by the cameras onboard. Navigators use methods like this back there is no GPS in abysmal amplitude and we can’t see the aircraft from Earth-based telescopes. From this point forward, though, the OSIRIS-REx aggregation will await on landmarks on Bennu’s apparent to clue OSIRIS-REx, a added absolute address that will ultimately adviser them to a sample-collection armpit bright of boulders and ample rocks, said Adam.
“After administering a all-around imaging and mapping attack during our contempo basic analysis phase, the science aggregation has created 3-D models of Bennu’s area that we’re activity to activate application for aeronautics about the asteroid,” she said.
Another analytical cold of this alternate phase, Adam said, is to get a bigger handle on Bennu’s accumulation and gravity, appearance that will access the planning of the blow of the mission, conspicuously the abbreviate touchdown on the apparent for sample accumulating in 2020. In the case of Bennu, scientists can alone admeasurement these appearance by accepting OSIRIS-REx actual abutting to the apparent to see how its aisle aeroembolism from Bennu’s gravitational pull.
“The Alternate A appearance will advice advance our abundant models for Bennu’s force field, thermal properties, orientation, and circuit rate,” said Wibben. “This, in turn, will acquiesce us to clarify our aisle designs for the alike added arduous flight activities we will accomplish in 2019.”
The December 31 action to abode the aircraft into apogee about Bennu is the aboriginal of abounding agitative aeronautics activities planned for the mission. The OSIRIS-REx aggregation will resume science operations in backward February. At that point, the aircraft will accomplish a alternation of abutting flybys of Bennu for several months to booty high-resolution images of every aboveboard inch of the asteroid to advice baddest a sampling site. During the summer of 2020, the aircraft will briefly blow the apparent of Bennu to retrieve a sample. The OSIRIS-REx mission is appointed to bear the sample to Earth in September 2023.