The spacecraft at the center of NASA's first asteroid sample return mission has altered its trajectory in preparation for its return to Earth next year.
On Sept. 21 OSIRIS-REx spacecraft fired its thrusters for 30 seconds for a course correction. This is the first time the spacecraft carrying a sample of the near-Earth asteroid Bennu has altered its trajectory since leaving the space rock on May 10, 2021.
Asteroids are made up of material that is left over from the beginning of the solar system and the formation of its planets, including Earth. Scientists hope that by studying the dust and rock OSIRIS-REx returns on Sept. 24, 2023, they could learn more about the building blocks of the solar system, and potentially even those of life itself.
The sample-return mission OSIRIS-REx, formally known as the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, is tasked with completing what is far from a straightforward "parcel drop," according to NASA.
The spacecraft must approach Earth with a precise speed and in the right direction to deliver the capsule containing the sample collected from Bennu to the planet's atmosphere safely.
"If the capsule is angled too high, it will skip off the atmosphere," Mike Moreau, OSIRIS-REx deputy project manager at NASA's Goddard Space Flight Center in Maryland, said in a statement. "Angled too low, it will burn up in Earth's atmosphere."
Additional course corrections like this one, therefore, will be essential over the coming year to ensure that the success of the seven-year-long mission, which launched on Sept. 8, 2016, and arrived at Bennu on Oct. 20, 2020.
If OSIRIS-REx stayed on its current trajectory, the spacecraft would pass Earth at a distance of about 1,370 miles (2,200 kilometers), so in July 2023, the spacecraft will begin a series of steering maneuvers.
"Over the next year, we will gradually adjust the OSIRIS-REx trajectory to target the spacecraft closer to Earth," Daniel Wibben, trajectory and maneuver design lead with KinetX Inc., which partners with Lockheed Martin's team that steers the spacecraft, said in the statement. "We have to cross Earth's orbit at the time that Earth will be at that same location."
The process will bring the spacecraft to around 155 miles (250 km) of Earth's surface. This is close enough to release its sample capsule into the atmosphere for a parachute-guided precision landing at the Air Force's Utah Test and Training Range in the Great Salt Lake Desert.
Next, NASA personnel will take the returned cargo to a newly built and specially engineered curation lab at Johnson Space Center in Houston. Scientists will use equipment such as specialized gloveboxes, tools and storage containers, all of which are being designed to keep the sample from being contaminated, and thus remain as close as possible to how it was when it was collected by OSIRIS-REx. Samples collected by the mission will also be sent to teams of scientists across the world and a large sample will be preserved for future generations to study.
Not all of the OSIRIS-REx mission's Bennu findings must wait for the sample, however.
Even before the spacecraft reaches Earth next year it has delivered data that could teach researchers more about the asteroid.
In July, scientists announced that data gathered by OSIRIS-REx about the surface of Bennu revealed that the asteroid is so loosely packed that if the spacecraft had attempted to land on it rather than firing its thrusters to back away quickly, it would have sunk beneath the asteroid's surface.
OSIRIS-REx has also provided NASA with data that is important in calculating the potentially hazardous object's future orbit until 2300. This information could be crucial in determining if Bennu, which has a diameter of 1,200 feet (490 meters), could impact Earth after its close approach in 2135.
"NASA's Planetary Defense mission is to find and monitor asteroids and comets that can come near Earth and may pose a hazard to our planet," Kelly Fast, program manager for the Near-Earth Object Observations Program at NASA, said in a 2021 statement.
"We carry out this endeavor through continuing astronomical surveys that collect data to discover previously unknown objects and refine our orbital models for them," she added. "The OSIRIS-REx mission has provided an extraordinary opportunity to refine and test these models, helping us better predict where Bennu will be when it makes its close approach to Earth more than a century from now."
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Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.