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WASHINGTON – NASA’s OSIRIS-REx spacecraft will make a final close-up approach to the asteroid it sampled next week before returning to Earth.
On April 7, the spacecraft will pass 3.7 kilometers over the location of the asteroid Bennu called Nightingale where, in October, the spacecraft briefly landed and collected up to several hundred grams of material, now stored in the spacecraft.
Immediately after this sample collection maneuver, the mission did not intend to return to the vicinity of Bennu. However, NASA decided to make a final pass at the landing site to see what changes the sampling made to the Nightingale area, such as the creation of a crater.
“We sat down and did a risk assessment, and we decided the risk was very low and the scientific feedback was very important. So we go back and look at the site and see if we can determine the crater, ”said Dante Lauretta, principal investigator for OSIRIS-REx at the University of Arizona, in a March 17 presentation on the mission at the 52nd. Lunar and Planetary Science Conference Online.
He predicted that the site should have not only a single crater, but up to five: one created by the sampling mechanism and four of the spacecraft’s thrusters that fired to slow the descent of the spacecraft and keep it away from it. the surface. “There should be five, or some sort of clover pattern to all of this interaction with the surface,” he says.
Analysis of the data collected during this October 20 sampling mechanism, at the end of a robotic arm extended from the bottom of the spacecraft, went deeper into the surface than expected. The sample head descended 48.8 centimeters below the surface before the spacecraft stopped its descent and began to ascend.
“The surface wasn’t slowing us down at all,” he said. “If we hadn’t fired the recoil thrusters, we probably would have plunged meters into the surface of this asteroid, which is fascinating to think.
Shortly after the sample collection maneuver, images showed material escaping from the sample head. This prompted the mission to speed up efforts to stow the Sample Collection Unit into a capsule that will store it during the return trip to Earth.
“We definitely lost tens of grams of sample from the time we collected it until the time we put it away,” Lauretta said. “We’re still convinced that there are substantial amounts of material in this ready-to-go home pod.”
Due to the accelerated effort to put away the sampling head, the mission did not attempt to accurately measure the amount of material stowed by spinning the spacecraft and measuring the difference in its moment of inertia before the sampling maneuver. However, visual estimates from the sampling head suggest that it contains at least several hundred grams of material. “We feel like we’ve collected a lot more than our 60 gram requirement,” he said.
The flight over the Nightingale site will be the last time OSIRIS-REx approaches Bennu. The spacecraft will begin its return trip to Earth on May 10 and arrive on September 24, 2023. The capsule containing the samples will land in the Utah desert. “We are very happy to receive these samples in our labs and learn about the history of Bennu and the solar system,” he said.
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