[music throughout] As we started to approach Bennu
from a distance and it started to fill up the camera field of view
it looked exactly like we thought it would
with a few boulders sticking out. But as we got closer we expected to see a very sandy surface
with maybe a few boulders here and there, and what we saw is
very little sand. And we saw these mountains, we saw boulders, we saw rocks
we saw very few areas that had this sandy surface that we were expecting and that we had designed for
We have never done this before.
We're actually going to collect a sample and bring it back down to Earth for further examination by scientists.
In order to achieve that objective
the OSIRIS-REx spacecraft has been navigating around Bennu for about the last two years
studying it in great detail, and also overcoming a number of challenges that Bennu has presented.
We were looking for locations on Bennu that were 50 meters in diameter
relatively flat and covered with fine-grained material.
and by fine-grained material, I mean stuff that's the size of a dime or smaller.
We realized that there were no sites on Bennu that even came close to meeting this criteria
Everywhere we looked was too small and covered with boulders
So we actually had to fly a number of additional close pases over the asteroid
and rethink our entire plan for grabbing the sample
After the additional observations of Bennu
we had to downselect to four sites
and then go back and survey those sites even further to select the final, primary sample site.
My first impression of Nightingale is - that's the last place I wanted to go.
but as we started looking at other sites, we saw that
one, this is probably one of the most sampleable sites
and two, we were overperforming in our navigation capability
and our ability to contact.
Natural feature tracking works a lot like the human mind
in that we pick up landmarks along the way
as we descend, we look at features on the ground
we program the computer to recognize certain features. It takes a picture, says - this feature is not where I expected it to be
it's a little bit off to the side
updates its position based on where its point and where that feature shows up in the camera position.
The TAG event is our Touch-and-Go event
which is where we'll actually be retrieving the sample from Asteroid Bennu
We start with a series of maneuvers, one of them being the CheckPoint burn
which is where we'll actually check our position and velocity in relation to the sample site
and then the MatchPoint burn about ten minutes later
will zero out our horizontal velocity relative to the surface
and then about ten minutes after that we make contact with the TAGSAM
fire the gas bottle, and then back away
and we hope to get at least 60 grams of sample, and then we'll be able to
store that and bring it back down to Earth.
But there are several things that could go wrong
and we also have to be prepared that we won't be successful
on our first try at Nightingale.
We don't only get one shot at TAG - we actually have three nitrogen bottles onboard the spacecraft
So we can potentially do 3 TAG attempts if needed.
We go through several "What if?" scenarios
and this is how we actually prepare for a lot of our contingencies
So we've had to look all around the surface and identify the
rocks and boulders that if the spacecraft were to tip over
up to 25 degrees, it could come in to contact and be damaged.
We had to develop a hazard map which we program into the computer
it says - if you're getting too close to those hazards
we'll do a wave-off, back away from the asteroid, come back and do this another day.
Everything might work perfectly -
we come down, we touch the surface
just where we want to
we fire the gas bottle
but the area we contact is covered in large rocks.
Those rocks would prevent any fine-grained material from being stirred up and captured in the TAGSAM head.
Another similar scenario is if the TAGSAM were to touch on the edge of a boulder and become tipped up.
In that case, when the gas bottle fires, much of that gas escapes out the sides
not churning up the material that we want to capture
The day of TAG is going to be really exciting
but the excitement for our team doesn't end there.
We have to verify that we have a proper sample.
First we're going to image the TAGSAM head by sticking it in front of one of the cameras
Then, we're going to do a maneuver called the sample mass measurement
in which we stick out the arm and spin the spacecraft in order to decide if we've collected enough mass
to be able to stow the sample and return home
or if we have to try again.
This the culmination of a lot of work
it's probably one of the most exciting missions that I've worked on
It is really exciting to know that we're finally going to be able to
touch the surface of an asteroid and collect a sample to return back to Earth