Touchdown! OSIRIS-REx TAGS Bennu

Touchdown! OSIRIS-REx TAGS Bennu

NASA’s OSIRIS-REx asteroid sample return spacecraft successfully executed a Touch-and-Go (TAG) maneuver today, touching the surface of asteroid Bennu just long enough — hopefully — to ingest at least 60 grams of soil. It will take a week or so to know for sure how much was obtained for return to Earth, but mission controllers were clearly ecstatic that the procedure taking place more than 200 million miles away went as planned.

The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx or O-REx) was launched in 2016 and arrived at Bennu in December 2018.  Since then it has been orbiting the asteroid and collecting scientific data including high resolution images.

One of the first things scientists discovered is that the surface is completely different than expected. Instead of expansive sandy areas where touching down would be easy, the surface is covered with rocks, big and small.

Asteroid Bennu. Credit NASA/Goddard, University of Arizona.

Over the past two years, mission controllers have had to figure out new ways to control the spacecraft and allow it to grab a sample of Bennu with its Touch-and-Go Sample Acquisition Mechanism (TAGSAM).

Today was the ultimate test.

Bennu is very small, about 500 meters in diameter or about the height of the Empire State Building. It has virtually no gravity, so O-REx cannot land. Instead it “kisses” the surface for a few moments.  NASA made two practice runs earlier this year, but today was the first actual attempt to obtain a sample.

Credit: NASA

Bennu is 207 million miles (334 million kilometers) from Earth. It takes 18.5 minutes for a signal to travel from O-REx to Lockheed Martin’s mission control facility near Denver, CO.  Lockheed Martin built the spacecraft and controls the mission.

At 6:12 pm Eastern Daylight Time, mission control announced “Touchdown Declared! Sampling in progress.”

As Principal Investigator (PI) Dante Lauretta of the University of Arizona had pointed out more than 10 minutes earlier, though, whatever had happened on Bennu was already over. Now it was a matter of waiting the 18.5 minutes for signals to arrive.

Arrive they did, each with better and better news. O-REx did touch down, a nitrogen canister fired to stir up material on the surface to be ingested into the sample collection device, and the spacecraft rose back up into orbit.

Whether or not a sample was obtained will not be known until next week when a camera on the spacecraft will look at the sample head to see if anything is there, and controllers will spin the spacecraft to determine if its moment of inertia changed, indicating more mass is aboard. The goal is to acquire at least 60 grams of material, but perhaps as much as 2 kilograms.

Illustration of OSIRIS-REx, with its sample arm extended, about to touch down on Bennu. Credits: NASA/Goddard/University of Arizona

If it turns out not enough was collected, O-REx can make two more tries.

By tomorrow, though, images taken during today’s event will arrive on Earth. The data rate is just 40 bits per second.  NASA will hold a press conference at 5:00 pm ET tomorrow to share what it knows by then.

Lauretta said “the team is overjoyed” at how everything went today.

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.”  Dante Lauretta

He and Thomas Zurbuchen, the head of NASA’s Science Mission Directorate, each paid tribute to Michael Drake, the original PI for the mission who passed away in 2011 shortly after the mission was approved for development. A plaque on the spacecraft honors him.

O-REx will depart Bennu in 2021 for its long trip back to Earth. The sample return canister will separate from the main spacecraft and land in the Utah desert on September 24, 2023.

NASA will exchange samples it returns from Bennu with those the Japan Aerospace Exploration Agency (JAXA) is bringing back from a different asteroid, Ryugu. This is JAXA’s second asteroid sample return mission. The first, Hayabusa, returned over 1,000 grains of asteroid Itokawa in 2010. Hayabusa2’s sample canister will land in Woomera, Australia on December 6, 2020.


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