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[music throughout] As we started to approach Bennu

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from a distance and it started to fill up the camera field of view

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it looked exactly like we thought it would

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with a few boulders sticking out. But as we got closer we expected to see a very sandy surface

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with maybe a few boulders here and there, and what we saw is 

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very little sand. And we saw these mountains, we saw boulders, we saw rocks

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we saw very few areas that had this sandy surface that we were expecting and that we had designed for

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We have never done this before.

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We're actually going to collect a sample and bring it back down to Earth for further examination by scientists.

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In order to achieve that objective

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the OSIRIS-REx spacecraft has been navigating around Bennu for about the last two years

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studying it in great detail, and also overcoming a number of challenges that Bennu has presented.

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We were looking for locations on Bennu that were 50 meters in diameter

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relatively flat and covered with fine-grained material.

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and by fine-grained material, I mean stuff that's the size of a dime or smaller.

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We realized that there were no sites on Bennu that even came close to meeting this criteria

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Everywhere we looked was too small and covered with boulders

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So we actually had to fly a number of additional close pases over the asteroid

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and rethink our entire plan for grabbing the sample

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After the additional observations of Bennu

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we had to downselect to four sites

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and then go back and survey those sites even further to select the final, primary sample site.

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My first impression of Nightingale is - that's the last place I wanted to go.

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but as we started looking at other sites, we saw that

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one, this is probably one of the most sampleable sites

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and two, we were overperforming in our navigation capability

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and our ability to contact.

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Natural feature tracking works a lot like the human mind

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in that we pick up landmarks along the way

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as we descend, we look at features on the ground

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we program the computer to recognize certain features. It takes a picture, says - this feature is not where I expected it to be

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it's a little bit off to the side

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updates its position based on where its point and where that feature shows up in the camera position.

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The TAG event is our Touch-and-Go event

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which is where we'll actually be retrieving the sample from Asteroid Bennu

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We start with a series of maneuvers, one of them being the CheckPoint burn

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which is where we'll actually check our position and velocity in relation to the sample site

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and then the MatchPoint burn about ten minutes later

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will zero out our horizontal velocity relative to the surface

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and then about ten minutes after that we make contact with the TAGSAM

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fire the gas bottle, and then back away 

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and we hope to get at least 60 grams of sample, and then we'll be able to

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store that and bring it back down to Earth.

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But there are several things that could go wrong

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and we also have to be prepared that we won't be successful 

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on our first try at Nightingale.

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We don't only get one shot at TAG - we actually have three nitrogen bottles onboard the spacecraft

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So we can potentially do 3 TAG attempts if needed.

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We go through several "What if?" scenarios

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and this is how we actually prepare for a lot of our contingencies

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So we've had to look all around the surface and identify the 

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rocks and boulders that if the spacecraft were to tip over

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up to 25 degrees, it could come in to contact and be damaged.

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We had to develop a hazard map which we program into the computer

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it says - if you're getting too close to those hazards

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we'll do a wave-off, back away from the asteroid, come back and do this another day.

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Everything might work perfectly -

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we come down, we touch the surface

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just where we want to

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we fire the gas bottle

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but the area we contact is covered in large rocks.

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Those rocks would prevent any fine-grained material from being stirred up and captured in the TAGSAM head.

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Another similar scenario is if the TAGSAM were to touch on the edge of a boulder and become tipped up.

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In that case, when the gas bottle fires, much of that gas escapes out the sides

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not churning up the material that we want to capture

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The day of TAG is going to be really exciting

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but the excitement for our team doesn't end there.

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We have to verify that we have a proper sample.

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First we're going to image the TAGSAM head by sticking it in front of one of the cameras

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Then, we're going to do a maneuver called the sample mass measurement

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in which we stick out the arm and spin the spacecraft in order to decide if we've collected enough mass

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to be able to stow the sample and return home

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or if we have to try again.

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This the culmination of a lot of work

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it's probably one of the most exciting missions that I've worked on

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It is really exciting to know that we're finally going to be able to

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touch the surface of an asteroid and collect a sample to return back to Earth