After orbiting Bennu for two years, OSIRIS-REx descended towards the asteroid and gathered a sample of rubble. The spacecraft is expected to make its return journey back to Earth in March 2021, arriving in September 2023. (Image Credit: NASA/Goddard/University of Arizona)
NASA has been busy. They found water on the Moon today (10/26/2020)! They are also planning to return a sample from a moving asteroid!
On October 20th, NASA’s OSIRIS-REx spacecraft landed on Bennu, an asteroid located over 200 million miles from Earth, and collected a sample of dust and pebbles from its surface. OSIRIS-REx launched in September 2016 and reached Bennu two years later, orbiting around the asteroid and precisely mapping it to find an area to pick up a sample. The spacecraft is set to make a return journey to Earth in March 2021, arriving in September 2023.
Bennu could provide scientists with a window into the early solar system as it was forming billions of years ago. The carbon-rich material from the asteroid could also help scientists understand how life originated on Earth.
It took four and a half hours for the spacecraft to descend from its orbit to Bennu’s surface. The spacecraft spread out the shoulder, elbow, and wrist of its 11-foot sampling robotic arm called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM). Afterward, it passed across the asteroid, measuring 1,670ft, while descending half a mile toward the surface. After the descent, at an altitude of 410 feet, OSIRIS-REx executed the “Checkpoint” burn, one of two maneuvers that allow it to target the sample collection site, called “Nightingale.”
Then, the spacecraft ignited its thrusters for the second “Matchpoint” burn, which slowed its descent and matched Bennu’s rotation when contact was made. Next, it traveled on an 11-minute coast past a boulder the size of a two-story building, known as “Mount Doom,” and landed on a clear area in a crater on Bennu’s northern hemisphere. Nightingale is one of the few clear spots found on the asteroid.
The spacecraft’s telemetry data revealed that the TAG event, which was performed autonomously, went according to plan. Real-time data showed that the TAGSAM made contact with the surface and shot out pressurized nitrogen gas to stir up dust and pebbles and captured it in the TAGSAM sample collection head. The team behind this mission said that OSIRIS-REx lifted off from the surface of Bennu.
The series of images show the asteroid particles drifting out of the TAGSAM head. Analysis reveals that the material is passing through tiny gaps where a mylar flap is jammed open by larger rocks. (Image Credit: NASA)
On October 22nd, NASA received confirmation that OSIRIS-REx collected rubble that weighs hundreds of grams, far more than the required amount (60 grams). The spacecraft took images of the sample collector head as it moved through different positions. These images revealed that the head is full of asteroid particles, and some of these particles are drifting away from the TAGSAM head. NASA also suspects that the material is passing through tiny gaps where a mylar flap is jammed open by larger rocks.
The team says the spacecraft has collected a sufficient sample and is storing it away as quickly as possible. To arrive at this conclusion, they compared images of the empty collector head with the TAGSAM head images taken on October 22nd. However, there may be more sample loss if the spacecraft and the TAGSAM instrument move around. To prevent further leakage, the team decided to forego the Sample Mass Measurement activity and canceled a braking burn to minimize the spacecraft’s acceleration.
A cloud of asteroid rubble could be seen moving around the spacecraft as it lifted off from Bennu. It showed that at least 5 to 10 grams drifted away at any given time.
Now, the OSIRIS-REx team is focusing on storing the sample in the Sample Return Capsule (SRC). This is where any loose rubble is preserved during the spacecraft’s return journey to Earth.
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