Historic occasion for NASA! The spacecraft OSIRIS-REx efficiently completes the touch-and-go maneuver on asteroid Bennu


Asteroid Bennu is one of the millions of asteroids in our solar system. (Image: NASA / Goddard / University of Arizona)

Asteroid Bennu sample collection: NASA has successfully completed the TAG maneuver on asteroid Bennu! The US space agency NASA attached a spring to the cap in the early hours of Wednesday and successfully completed the first attempt at an asteroid sampling mission. NASA's OSIRIS-REx spacecraft, orbiting the Bennu asteroid since late December 2018, performed a touch-and-go or TAG maneuver to collect the sample from the asteroid's surface. The mission proceeded exactly according to the projected time axis, and the spacecraft's sample-collecting arm touched the asteroid for between five and 15 seconds. While the first attempt to collect samples was successful on the safe landing and takeoff, it would take the team a few days to determine whether or not OSIRIS-REx was able to collect a sample.

Asteroid Bennu sample collection: About the mission

In September 2016, NASA launched the Origins, Spectral Interpretation, Resource Identification, Security and Regolith Explorer (OSIRIS-REx) spacecraft to orbit the asteroid and then collect samples from its surface. The mission was an idea by Dr. Michael J Drake, who, along with Dante Lauretta, repeatedly proposed to NASA that a mission should be allowed to go to an asteroid for sampling. After seven years of work on proposals, Dr. Drake and Lauretta finally accepted the space agency's proposal for the mission. In an unfortunate turn of events, Dr. Drake, however, a few months after approval.

Lauretta is now the Mission's lead investigator, and there were tears in his eyes when he contacted Dr. Drake recalled when the NASA team confirmed that the OSIRIS-REx touch-and-go maneuver had been a success.

Asteroid Bennu is one of the millions of asteroids in our solar system. However, it is not part of the main asteroid belt between Mars and Jupiter. Asteroid Bennu is a near-Earth asteroid, and scientists believe it contains clues about the formation of the solar system and planets.

Lauretta said during the live broadcast of the TAG mission that Bennu was selected because the team needed a near-Earth object with an orbit similar to that of Earth. In fact, Bennu's orbit is through Earth orbit. He added that the mission was aimed at finding answers to some basic questions, such as why there is life in the solar system, why the earth has a habitable environment, and how life was actually formed. He said that asteroid Bennu is rich in water and carbon, one of many, and it could help provide clues as to how oceans were formed on the planet. He added that it is almost certain that the water on Earth was brought by asteroids like Bennu, creating a link between human life and the asteroids.

Lauretta added that understanding the asteroid is also important as it is a potentially dangerous asteroid that could cause serious damage to the Earth if it collided. In fact, he said there was a possibility that Bennu could collide with Earth about 150 years later. Therefore, OSIRIS has tried to study Bennu's orbit very carefully and understand the effects of the sun on the orbit so that possible changes that could lead to a collision with the earth can be foreseen and implemented in advance.

How does OSIRIS-REx work?

The OSIRIS-REx spacecraft was deployed about 321 million kilometers from Earth. This means that all data transmitted from the control room on earth to the spaceship or vice versa takes more than 18.5 minutes to be received. This required the need for a spacecraft that was intelligent and equipped to make its own decisions while navigating space and particularly during the sampling attempt.

That being said, the images transmitted by the spaceship during the TAG maneuver were of poor quality, just enough for the team to know how the maneuver was progressing. OSIRIS will send high-quality close-ups of the asteroid as soon as it is back in its orbit around Bennu and is charged by sunlight.

The OSIRIS also had to be programmed to adapt to certain challenges posed by Asteroid Bennu. Before OSIRIS was deployed, the asteroid was mapped using thermal images, based on which scientists believed the asteroid had a beach-like surface. However, as the OSIRIS approached the asteroid, the increasingly detailed images surprised the scientists when they saw that its surface was littered with boulders and stones.

This was a challenge for the scientists, as they then had to program OSIRIS in such a way that, in addition to the asteroid's already high rotational speed, it lands under much more difficult terrain and takes off from Bennu. For the TAG maneuver, based on the images transmitted by the spaceship during the asteroid's orbit, the scientists focused on the Nightingale crater. While the crater is surrounded by huge boulders, there is an 8-meter area that seemed optimal for sampling.

However, the scientists had previously hoped for an area of ​​50 meters, and that significant reduction required additional features that came in the form of Natural Features Tracking (NFT). This was the first time the system has been used in space. In this way OSIRIS analyzed in real time whether the sampling point was suitable while descending. The scientists had demarcated dangerous and safe terrain, and with it the spaceship was examining the surface of the asteroid to determine possible damage. To be completely sure that the spaceship remained safe, it could also abort the TAG maneuver if the surface was dangerous and instead retreat into space from a height of 5 meters above the surface.

Fortunately, in completing the mission, the need to abort the mission was not identified.

However, an additional challenge for Bennu was the microgravity field. This made collecting samples difficult, as any force the spaceship exerted while collecting samples would cause it to ricochet off Bennu. For this purpose, the spaceship was equipped with a sample arm called the TAG Sample Acquisition Mechanism or TAGSAM, which had a bowl-like head. To collect the sample, the TAGSAM was fitted with three bottles of nitrogen gas.

In a single experiment, a bottle of nitrogen dispenses at high speed, creating a kind of vacuum. In addition, this burst also moves particles on the surface, which causes the vacuum and movement to trap some of the surface material in the TAGSAM sample collection head. Scientists want to bring back 60 grams of matter.

What now?

Over the next few days, the scientists would confirm whether or not a sample actually took place by examining the images of the Nightingale site before and after the TAG and comparing the weight of the TAGSAM after the mission with the previously recorded weight. These dates are expected to be back by Saturday. If the collection is successful, the scientists will order OSIRIS-REx to begin returning to Earth. Otherwise it will be prepared for a second attempt to land in January next year.

OSIRIS is expected to return to Earth with the samples by 2023.

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Steven Gregory