A final rapprochement of the OSIRIS-REx probe with the asteroid Bennu is scheduled for April 7, 2021. NASA thus wants to observe how the collection of the sample in October could have disturbed the surface of the object.
How much did the OSIRIS-REx probe disturb Bennu’s surface by collecting a sample there last October? NASA is preparing to find out this Wednesday, April 7, 2021. The space agency has planned a final overflight of the asteroid, which was not in the initial program of the mission, before starting the return trip to Earth.
On this occasion, the space probe must observe the object at a distance of about 3.7 kilometers. OSIRIS-REx has not been so close to the asteroid since October 20, when the sample was taken. The space agency finally decided to get closer to Bennu one last time, to see the “damage” left by OSIRIS-REx during the sample.
“A dramatic effect on the sampling site”
This sample was taken from a site called Nightingale, which is located in the northern hemisphere of the asteroid. While collecting the sample, the TAGSAM system (for “Touch-And-Go Sample Acquisition Mechanism”) momentarily touched Bennu. The sampling head sank 48.8 centimeters below the surface, releasing nitrogen to lift the regolith (a layer of soil made up of dust and covering rock).
In addition to that, the probe’s recoil maneuver must also have disturbed the material on Bennu’s surface. As NASA explains, the gravity on the asteroid is low: we can expect ” a dramatic effect on the sampling site », With rocks and dust displaced by OSIRIS-REx. By approaching Bennu once again, the probe will help scientists estimate how that contact may have changed the appearance of the asteroid there.
Concretely, this flyby resembles a previous maneuver carried out by the mission in 2019, during a sequence of observation of Bennu. For a little less than 6 hours (which is equivalent to a period of almost total rotation of the object), the probe will photograph the asteroid. The images taken by OSIRIS-REx can then be compared with those obtained in 2019. In addition, the approach will provide an opportunity for the mission teams to assess the state of the various scientific instruments of the probe, because some have may have been covered with dust when collecting in October. However, estimating the state of the instruments is important from the perspective of perhaps extending the OSIRIS-REx mission after the return of the sample capsule to Earth.
It will take several days for NASA to obtain the data. After this ultimate flyover, OSIRIS-REx will be able to leave the vicinity of the asteroid for good and return to our planet. Its return trip must begin in May, so that the sample arrives on Earth on September 24, 2023. The probe will then have to drop the capsule in the Utah desert.
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