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The OSIRIS-REx mission is an
asteroid sample return mission

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and the main goal is to collect
60 grams of pristine sample from

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the surface of the near-Earth
asteroid Bennu. Bennu’s rocky

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surface presented a challenge
for the original LIDAR-based

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approach to the Touch-and-Go
sample acquisition event. As an

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alternative, the project
developed an onboard, optical

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based approach called Natural
Feature Tracking. NFT requires

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detailed, 3-dimensional maps of
the surface of Bennu. In order

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to build those 3-dimensional
maps, we needed many many images

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of particular patches of the
surface on Bennu itself. So, all

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these surveys that we’ve done
throughout the mission have been

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at distances between several
kilometers from the asteroid,

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down to just a few hundred
meters from the surface. And

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based on those different
perspectives and what the

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shading of the terrain is, it is
possible to build a 3D model.

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Very similar to how we have two
eyes that allow us to have depth

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perception of what we see, NFT
requires multiple features

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across the field of view to have
a depth perception. The original

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TAG accuracy requirement was to
touch the surface within a

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50-meter diameter circle. Based
on Bennu’s rough surface, our

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actual performance has to be
much better than that, at

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10-meters or less. And even
within that 10-meter area, there

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could be smaller, localized
hazards that may damage the

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spacecraft. Right now, we are
working on a flight software

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patch to help us avoid hazards
as we come in for our sample

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event. When we do Natural
Feature Tracking, that is all

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autonomous onboard the
spacecraft – where we load the

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features, or a catalog to the
spacecraft – so we are telling

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it where we expect these
features to be. So, as the

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spacecraft makes its progress
down to taking the sample, we’re

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recording images and then
locating those landmarks to make

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sure we’re on the right track.
And if there are any issues with

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the trajectory or we see
landmarks where we shouldn’t, we

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know something’s up and we can
back away and wave off the

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attempt and try again.