The OSIRIS-REx spacecraft has been in orbit around the Bennu asteroid since late 2018. Mission – Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer – Launched in September 2016.
Since Bennu’s arrival, the spacecraft and its cameras have been collecting and returning data and images to help the team map the best landing sites to learn more about the composition of the asteroid and collect samples.
The main event of the mission, called the Touch-and-Go Sample Collection Event or TAG, is scheduled for October 20 at 5 pm at ET.
The asteroid and spacecraft are currently 207 million miles from Earth, with a communication delay of approximately 18.5 minutes. Live stream animation that describes what is happening based on instructions already sent to OSIRIS-REx for a sample collection sequence by a team at NASA.
Since direct commands from Earth are not possible, the spacecraft does the entire sequence of approaching the asteroid and automatically collecting the sample.
Based on the data returned by the spacecraft, the mission team should be able to confirm whether the touchdown was successful on Tuesday.
The spacecraft actually conducted two rehearsals without touching the asteroid, so the team prepared for the much-anticipated event.
However, scientists did not expect Bennu. The Nightingale landing site is surrounded by dangers, so the mission must be executed with great precision.
The OSIRIS-REx spacecraft must detect hazards and delay its own mission if there are any obstacles to sample collection. If everything goes smoothly, the spacecraft and its valuable prototype will embark on a long journey back to Earth next year and land on Earth in 2023.
Dodging building-sized boulders
Hold a van that can carry up to 15 passengers in space and reach the height of the Empire State Building and a rapidly spinning rock. This is the OSIRIS-REx mission to Bennu.
Bennu has an orbit that is close to Earth, so it is considered to be the closest asteroid to Earth. One of its future policies is to bring it closer to Earth in the next century; It is one of only 2,700 to have an impact on our planet.
The models from Bennu allow scientists to understand not only the asteroids that affect the Earth but also how the planets formed and life began. In total, it collects 2 ounces or 30 packets of sugar from the spaceship.
Although it may seem small, it is the largest prototype from space since the Apollo program, according to NASA.
First, you need to navigate a short, narrow path to the Nightingale landing site inside a crater in the northern hemisphere of the OSIRIS-REx asteroid.
The touchdown area was reduced to one-tenth in the original plan, so accuracy was crucial. At the eastern edge of the crater is a building-sized boulder that could threaten the spacecraft as it retreats from the asteroid once the sample is collected.
Bennou “The sandy beach we’m and look forward to is almost not there,” Thomas Zurbuchen, associate administrator at NASA’s Science Mission Directorate, told a news conference in September.
Instead, scientists have discovered that the asteroid is covered with house-sized boulders. The team used the spacecraft to map the entire asteroid and determine four potential landing sites. Nightingale was finally selected as the best.
“We chose Nightingale because it contains the very best materials among the four sample site candidates so far,” said Dante Loretta, the mission’s lead researcher and professor at the University of Arizona Lunar and Planetary Laboratory in September.
“We spent the early 2020s passing low-level surveillance on this site, eventually imaging an eighth of an inch per pixel. We basically had amazing images that covered the entire crater and we counted all those rocks.”
Going for touchdown
The Nightingale landing site is 52 feet in diameter, about the size of some parking lots, where the van-size spacecraft briefly touches down for a few seconds. There is no room for error; The building-sized boulders are a few feet away.
The event will take 4.5 hours to unravel and will run three maneuvers to collect the spacecraft model.
The spacecraft first left its safe orbit around the asteroid at 2,500 feet from the surface and traveled for four hours before reaching a distance of just 410 feet. Then, the spacecraft adjusts for position and speed to continue the descent.
Next, OSIRIS-REx slows its descent to target a path, so it coincides with the rotation of the asteroid during contact. The spacecraft is folded into a Y-wing configuration above to protect its solar panels.
Eventually, OSIRIS-REx will touchdown in less than 16 seconds. The spacecraft fires a pressure bottle of nitrogen into the meteorite, using the gas as a means of lifting matter off the surface of Bennu.
The collector head of the spacecraft captures the shaken material. Located in an 11-foot-long robotic sampling arm, this head is only one part of the spacecraft that touches Bennu. The team compares it to an air filter in an older model car, which is perfect for collecting fine materials.
There are even small disks on the head that can collect dirt, such as sticky pads, if part of the sample maneuver does not go as planned.
The camera collection on the spacecraft captures footage of the event.
“If we bend over, the gas flies to the side, we can tell if the material is moving enough,” Loretta said. “We have a very good indication of the exact location of the nightingale we introduced and we can compare it with our Samplability Map, to assess if we have touched an area with abundant sample materials or one of the rocker sites.”
Then, the spaceship’s thrusters fire and help Bennu pull back from the surface and once again reach a safe distance.
The OSIRIS-REx spacecraft will go through these maneuvers by itself and eventually decide whether it is safe. The spacecraft relies on its natural feature tracking navigation system, which actively captures images during landing and compares them with images stored in the onboard catalog to ensure they are on the right track. It affects every step of the descent and process.
If it leaves the course, the spaceship will stop this attempt.
The navigation system also includes a hazard map of the landing site, and if it detects that the spacecraft is approaching danger, it will stop at a height of 16 feet from the asteroid and will not continue with the effort.
This means that OSIRIS-REx is safe and can be tried for another sample collection in the future.
Checking with earth
At each stage, the spacecraft returns data to NASA researchers on Earth, which allows it to determine whether the touchdown was successful. Due to the epidemic only a limited number of teams will be in the Lockheed Martin space mission support area, while others will be on-site at various locations to monitor the event.
To make sure the spacecraft actually collected a sample, one of the OSIRIS-REx cameras will take pictures of the collection head on October 22nd. And on October 24, the spacecraft will perform a spin to determine the mass of material it has collected.
Although aimed at 2 ounces, OSIRIS-REx can hold up to 4 pounds.
If the sample collection goes as planned, the head and sample will be placed in the return capsule and closed to return to the ground.
If the collection fails or there is not enough material, there are two more nitrogen charges for future efforts at a second site called Osprey in January 2021.
In total, the team members spend a week evaluating what they have collected and ensuring that the spacecraft and its equipment do not escape the encounter.
“So far, the result for us on October 20 is that we will contact the surface and come away with a larger sample than we need. But Bennu has already thrown us several curve balls, so we’re fully ready to tag it at the Osprey (backup site) if necessary.” Mike Morey, deputy project manager at NASA’s Goddard Space Flight Center in Maryland, said in a statement.
Scientists have recently discovered that fine material from the Nightingale site has been exposed to the atmosphere. This means that the material collected by OSIRIS-REx is the most natural material on the asteroid.
The pattern of Bennu returning to Earth is not the same as the meteorites on Earth, NASA scientists said, because what they learned about Bennu was very, very unexpected.