[Music]
OSIRIS-REx is a NASA
mission to explore near-Earth
asteroid Bennu, a remnant from
the dawn of the solar system,
and to return a
sample of Bennu to Earth.
On September 8, 2016, OSIRIS-REx
began its journey to Bennu from
Cape Canaveral, Florida
aboard an Atlas V rocket.
It lifted off shortly before
sunset, climbing eastward over
the Atlantic Ocean to traverse
the night side of Earth.
One hour later, OSIRIS-REx
separated from its Centaur upper
stage rocket and
drifted into space.
It deployed its solar arrays to
catch the rising sun, and made a
final pass over Australia before
embarking on its outbound cruise
to Bennu.
After a year in orbit around the
sun, OSIRIS-REx briefly returned
to Earth in September
2017 for a gravity assist.
The spacecraft passed within
18,000 kilometers of Antarctica,
then turned its instrument deck
toward home to capture images
and spectra of
Earth and the Moon.
The gravity assist bent the
trajectory of OSIRIS-REx by six
degrees, matching the orbital
tilt of Bennu, and sending the
spacecraft on a path
to catch its target.
In August 2018, OSIRIS-REx
began its Approach phase.
Its long-range camera captured
the first visible-light images
of Bennu as a single pixel
moving across a field of stars.
Over the following months, Bennu
grew from a pixel into a world,
with OSIRIS-REx revealing its
shape, rotation, and color for
the first time.
Now, after chasing its target
for over two years, OSIRIS-REx
is arriving at asteroid Bennu.
On December 3 it will fire
its thrusters to match Bennu's
velocity and begin
its Preliminary Survey.
OSIRIS-REx will pass high
above the equator and the poles,
measuring Bennu's position and
mass, and refining its size,
shape, and spin.
On New Year's Eve, OSIRIS-REx
will venture close enough to
Bennu to be captured into orbit
by its miniscule gravity, making
it the smallest world ever to
be orbited by a spacecraft.
In early 2019, OSIRIS-REx
will break orbit to conduct a
Detailed Survey of Bennu.
First, it will carry out a
mapping campaign called the
Baseball Diamond.
By observing Bennu at different
latitudes and times of day,
OSIRIS-REx will capture stereo
images and identify large rocks
on the surface that could pose
a hazard later in the mission.
In its second mapping campaign,
OSIRIS-REx will observe Bennu
from seven different
stations around its equator.
At each station, it will take
measurements from pole-to-pole
using its mapping camera,
laser altimeter, and two
spectrometers.
The combined data will provide
a detailed look at Bennu's
geologic features
and its composition.
This will improve landmark-based
navigation, and enable mission
planners to begin looking for
places to collect a sample.
Following the Detailed Survey,
OSIRIS-REx will once again enter
orbit.
At a radius of only one
kilometer, Orbital B will serve
as the mission's safe home
orbit until sample collection.
During this phase, OSIRIS-REx
will globally map Bennu.
It will fly in a polar orbit as
the asteroid rotates beneath,
enabling full
coverage of the surface.
Orbital B's precession, or
wobble, will also be used to
measure Bennu's gravity field,
along with the non-gravitational
forces that are slowly
altering Bennu's trajectory.
In mid-2019, OSIRIS-REx will
begin its Reconnaissance phase.
It will break orbit and fly over
four candidate sample sites at
225 meters, taking
high-resolution images.
Flying at such close proximity
will reveal large pebbles that
could pose a hazard
during sample collection.
Mission planners will use this
information to select the two
best sites for
additional inspection.
At a range of 525 meters,
OSIRIS-REx will fly over the two
final candidate sites,
spectrally mapping the surface
to reveal its
chemical composition.
This information will help
mission planners determine the
most valuable site for
collecting the sample.
Once the final site has been
selected, OSIRIS-REx will begin
its rehearsal phase.
Frist, it will practice
autonomous flight to a
predetermined Check Point, where
it will start its descent during
sample collection.
Next, OSIRIS-REx will practice
flying to the Match Point.
The spacecraft will lower to
within 30 meters of the surface
to match Bennu's speed and
rotation, a necessity for safely
touching the asteroid.
Finally, in mid-2020, OSIRIS-REx
will be ready to collect a
sample of Bennu.
Before it descends to the
surface, the spacecraft will
deploy its Touch-And-Go
Sample Acquisition-Mechanism, or
TAGSAM, a new technology
invented for the mission.
When it reaches the Check Point,
OSIRIS-REx will begin its final
descent.
It will pull back is solar
arrays for safety, and approach
the surface at centimeters per
second, the walking pace of an
insect.
As the TAGSAM touches down, it
will blow high-pressure nitrogen
gas into the soil,
stirring up loose material.
A filter within the sample head
will trap rocks and dirt, while
allowing the gas
to escape to space.
Once the sample is collected,
OSIRIS-REx will fire its
thrusters and back away from
Bennu, retreating to a safe
distance with its
precious cargo.
Following collection, OSIRIS-REx
will verify the status of the
sample, using a
camera called SamCam.
This visual inspection will
reveal whether any large debris
is still attached to the sample
head, which could pose a hazard
during stowage.
Next, OSIRIS-REx will
verify the mass of the sample.
It will fully extend its TAGSAM
arm and perform a spin maneuver,
measuring the change in inertia
to determine the sample's mass.
If at least 60 grams have been
collected, and the sample head
is clear of hazardous debris,
mission planners will command
the spacecraft to
stow the sample.
StowCam will watch closely
as the sample head enters the
return capsule and
is secured in place.
OSIRIS-REx will then detach the
TAGSAM arm from the head, seal
the sample return capsule, and
prepare for its journey back to
Earth.
After departing from Bennu in
early 2021, OSIRIS-REx will
return to Earth in late 2023.
Four hours prior to arrival,
the spacecraft will release the
sample return capsule, then
deflect away from Earth to its
final orbit, as its
piece of Bennu comes home.
The capsule will enter the
atmosphere over the night side
of Earth, streaking towards the
central California coastline at
over 12 kilometers per second.
West of the Great Salt Lake, at
an altitude of approximately 33
kilometers, the capsule will
initiate its parachute sequence,
stabilizing and
slowing its descent.
Upon landing in the Utah desert,
the sample will be recovered,
carefully removed from the
capsule, and taken to the
OSIRIS-REx curation facility at
NASA's Johnson Space Center in
Houston, Texas.
This pristine material from
the early solar system will be
studied for decades to come,
providing clues to the formation
of the planets, to the evolution
of Earth, and to the ingredients
that were present at
the origins of life.
[Music]
138
00:07:35,488 --> 00:07:27,447
[Satellite  beeping]
