NASA's OSIRIS-REx spacecraft successfully touches asteroid

Date:
October 20, 2020
Source:
NASA
Summary:
NASA's Origins, Spectral Interpretation, Resource Identification,
Security, Regolith Explorer (OSIRIS-REx) spacecraft unfurled
its robotic arm Tuesday, and in a first for the agency, briefly
touched an asteroid to collect dust and pebbles from the surface
for delivery to Earth in 2023.



FULL STORY ========================================================================== [NASA's OSIRIS-REx | Credit: NASA/Goddard/University of Arizona] NASA's OSIRIS-REx mission readies itself to touch the surface of asteroid Bennu.

Credit: NASA/Goddard/University of Arizona [NASA's OSIRIS-REx | Credit: NASA/Goddard/University of Arizona] NASA's OSIRIS-REx mission readies
itself to touch the surface of asteroid Bennu.

Credit: NASA/Goddard/University of Arizona Close NASA's Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft unfurled its robotic arm Tuesday, and in a first
for the agency, briefly touched an asteroid to collect dust and pebbles
from the surface for delivery to Earth in 2023.


==========================================================================
This well-preserved, ancient asteroid, known as Bennu, is currently
more than 200 million miles (321 million kilometers) from Earth. Bennu
offers scientists a window into the early solar system as it was first
taking shape billions of years ago and flinging ingredients that could
have helped seed life on Earth.

If Tuesday's sample collection event, known as "Touch-And-Go" (TAG),
provided enough of a sample, mission teams will command the spacecraft
to begin stowing the precious primordial cargo to begin its journey back
to Earth in March 2021.

Otherwise, they will prepare for another attempt in January.

"This amazing first for NASA demonstrates how an incredible team from
across the country came together and persevered through incredible
challenges to expand the boundaries of knowledge," said NASA Administrator
Jim Bridenstine.

"Our industry, academic, and international partners have made it possible
to hold a piece of the most ancient solar system in our hands." At 1:50
p.m. EDT, OSIRIS-REx fired its thrusters to nudge itself out of orbit
around Bennu. It extended the shoulder, then elbow, then wrist of its
11-foot (3.35-meter) sampling arm, known as the Touch-And-Go Sample
Acquisition Mechanism (TAGSAM), and transited across Bennu while
descending about a half- mile (805 meters) toward the surface. After
a four-hour descent, at an altitude of approximately 410 feet (125
meters), the spacecraft executed the "Checkpoint" burn, the first of
two maneuvers to allow it to precisely target the sample collection
site, known as "Nightingale." Ten minutes later, the spacecraft fired
its thrusters for the second "Matchpoint" burn to slow its descent and
match the asteroid's rotation at the time of contact. It then continued
a treacherous, 11-minute coast past a boulder the size of a two-story
building, nicknamed "Mount Doom," to touch down in a clear spot in a
crater on Bennu's northern hemisphere. The size of a small parking lot,
the site Nightingale site is one of the few relatively clear spots on
this unexpectedly boulder-covered space rock.

"This was an incredible feat -- and today we've advanced both science
and engineering and our prospects for future missions to study these
mysterious ancient storytellers of the solar system," said Thomas
Zurbuchen, associate administrator for NASA's Science Mission Directorate
at the agency's headquarters in Washington. "A piece of primordial rock
that has witnessed our solar system's entire history may now be ready
to come home for generations of scientific discovery, and we can't wait
to see what comes next." "After over a decade of planning, the team
is overjoyed at the success of today's sampling attempt," said Dante
Lauretta, OSIRIS-REx principal investigator at the University of Arizona
in Tucson. "Even though we have some work ahead of us to determine the
outcome of the event -- the successful contact, the TAGSAM gas firing,
and back-away from Bennu are major accomplishments for the team. I look
forward to analyzing the data to determine the mass of sample collected."


==========================================================================
All spacecraft telemetry data indicates the TAG event executed as
expected.

However, it will take about a week for the OSIRIS-REx team to confirm
how much sample the spacecraft collected.

Real-time data indicates the TAGSAM successfully contacted the surface and fired a burst of nitrogen gas. The gas should have stirred up dust and
pebbles on Bennu's surface, some of which should have been captured in
the TAGSAM sample collection head. OSIRIS-REx engineers also confirmed
that shortly after the spacecraft made contact with the surface, it
fired its thrusters and safely backed away from Bennu.

"Today's TAG maneuver was historic," said Lori Glaze, Planetary Science Division director at NASA Headquarters in Washington. "The fact that we
safely and successfully touched the surface of Bennu, in addition to all
the other milestones this mission has already achieved, is a testament to
the living spirit of exploration that continues to uncover the secrets
of the solar system." "It's hard to put into words how exciting it
was to receive confirmation that the spacecraft successfully touched
the surface and fired one of the gas bottles," said Michael Moreau,
OSIRIS-REx deputy project manager at NASA's Goddard Space Flight Center
in Greenbelt, Maryland. "The team can't wait to receive the imagery from
the TAG event late tonight and see how the surface of Bennu responded
to the TAG event." The spacecraft carried out TAG autonomously, with pre-programmed instructions from engineers on Earth. Now, the OSIRIS-REx
team will begin to assess whether the spacecraft grabbed any material,
and, if so, how much; the goal is at least 60 grams, which is roughly equivalent to a full-size candy bar.



========================================================================== OSIRIS-REx engineers and scientists will use several techniques to
identify and measure the sample remotely. First, they'll compare images
of the Nightingale site before and after TAG to see how much surface
material moved around in response to the burst of gas.

"Our first indication of whether we were successful in collecting a sample
will come on October 21 when we downlink the back-away movie from the spacecraft," Moreau said. "If TAG made a significant disturbance of the surface, we likely collected a lot of material." Next, the team will
try to determine the amount of sample collected. One method involves
taking pictures of the TAGSAM head with a camera known as SamCam, which
is devoted to documenting the sample-collection process and determining
whether dust and rocks made it into the collector head. One indirect
indication will be the amount of dust found around the sample collector
head. OSIRIS-REx engineers also will attempt to snap photos that could,
given the right lighting conditions, show the inside of the head so
engineers can look for evidence of sample inside of it.

A couple of days after the SamCam images are analyzed, the spacecraft will attempt yet another method to measure the mass of the sample collected by determining the change in the spacecraft's "moment of inertia," a phrase
that describes how mass is distributed and how it affects the rotation
of the body around a central axis. This maneuver entails extending the
TAGSAM arm out to the side of the spacecraft and slowly spinning the
spacecraft about an axis perpendicular to the arm. This technique is
analogous to a person spinning with one arm extended while holding a
string with a ball attached to the end. The person can sense the mass
of the ball by the tension in the string. Having performed this maneuver
before TAG, and now after, engineers can measure the change in the mass
of the collection head as a result of the sample inside.

"We will use the combination of data from TAG and the post-TAG images
and mass measurement to assess our confidence that we have collected at
least 60 grams of sample," said Rich Burns, OSIRIS-REx project manager at Goddard. "If our confidence is high, we'll make the decision to stow the
sample on October 30." To store the sample, engineers will command the
robotic arm to place the sample collector head into the Sample Return
Capsule (SRC), located in the body of the spacecraft. The sample arm
will then retract to the side of the spacecraft for the final time,
the SRC will close, and the spacecraft will prepare for its departure
from Bennu in March 2021 -- this is the next time Bennu will be properly aligned with Earth for the most fuel-efficient return flight.

If, however, it turns out that the spacecraft did not collect enough
sample at Nightingale, it will attempt another TAG maneuver on Jan. 12,
2021. If that occurs, it will touch down at the backup site called
"Osprey," which is another relatively boulder-free area inside a crater
near Bennu's equator.

OSIRIS-REx launched from Cape Canaveral Air Force Station in Florida
Sept. 8, 2016. It arrived at Bennu Dec. 3, 2018, and began orbiting the asteroid for the first time on Dec. 31, 2018. The spacecraft is scheduled
to return to Earth Sept. 24, 2023, when it will parachute the SRC into
Utah's west desert where scientists will be waiting to collect it.

Goddard provides overall mission management, systems engineering and
the safety and mission assurance for OSIRIS-REx. Dante Lauretta of
the University of Arizona, Tucson, is the principal investigator, and
the University of Arizona also leads the science team and the mission's
science observation planning and data processing. Lockheed Martin Space in Denver built the spacecraft and is providing flight operations. Goddard
and KinetX Aerospace are responsible for navigating the OSIRIS-REx
spacecraft. OSIRIS-REx is the third mission in NASA's New Frontiers
Program, which is managed by NASA's Marshall Space Flight Center in
Huntsville, Alabama, for the agency's Science Mission Directorate in Washington.

For more information on OSIRIS-REx:
* https://www.nasa.gov/osiris-rex * https://www.asteroidmission.org

========================================================================== Story Source: Materials provided by NASA. Note: Content may be edited
for style and length.


==========================================================================


Link to news story: https://www.sciencedaily.com/releases/2020/10/201020184134.htm

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