The collection of touch and motion samples (TAG) of asteroid 101955 Bennu will stop on Tuesday, October 20, around 15:12 PT. NASA will broadcast the TAG maneuver live on NASA television and the agency’s website, starting at 2:00 p.m. Tuesday. You can find the live link below.
When did the mission start?
Osiris-Rex as a concept has existed since at least 2004, when a team of astronomers first proposed the idea to NASA. After more than a decade of development, the spacecraft, on top of the Atlas V rocket from the United Launch Alliance, a joint venture of Lockheed Martin and Boeing. The spacecraft spent the next 26 months sailing to Bennu, officially arriving on December 3, 2018.
Since then, the mission team has spent nearly two years in orbit around the diamond space rock, exploring and mapping its surface to choose the best place to sample. Rehearsals have begun in recent months before the upcoming sampling attempt, and now the team says they are ready to play TAG with Bennu.
Bennu is what is called an asteroid “pile of debris”, which means that it was formed in the deep cosmic past, when gravity slowly formed together the remnants of an ancient collision. The result is a body in the shape of a rotating peak with a diameter of about a third of a mile (500 meters) and a surface dotted with large stones and gems.
Bennu is believed to be a window into the past of the solar system: a virgin, carbon-rich body that carries the building blocks of both planets and life. Some of these resources, such as water and metals, may also be worth extracting at some point in the future for use on Earth or in space exploration.
The asteroid has another feature that makes it especially interesting for scientists and humans in general – it has a chance to affect the Earth in the distant future. In NASA’s list of risks of impact, Bennu is ranked second. Current data shows dozens of potential impacts in the last quarter of the 22nd century, although they all have only a one-minute chance of actually happening.
How will TAG work?
For anyone who has ever been involved in robots or perhaps even participated in a robotics competition, the Osiris-Rex mission seems to be the ultimate culmination of a young robot’s dreams. The “touch and move” sampling procedure is a complex, high-stakes task that is built to a key climax in years. If it succeeds, it will play a role in our history and future in space.
The main plan is for Osiris-Rex to touch Bennu on a rock. The minibus-sized spacecraft will have to contract building-sized stones around the landing area to touch a relatively clean space that is as large as a few parking spaces. However, the robotic sampling arm will be the only part of Osiris-Rex that will actually remain on the surface. One of the three pressurized nitrogen containers will fire to mix sample dust and small rocks, which can then be captured in the collector head of the hand for safe storage and return to Earth.
The descent to the surface of Bennu will take about four hours, approximately the time it takes the asteroid to make a complete revolution. Following this slow approach, the actual TAG sampling procedure remarkably took less than 16 seconds.
Preparations for the TAG did not go exactly as planned. Initially, the mission organizers hoped that Bennu’s surface would have many potential landing sites, covered mostly with fine materials comparable to sand or gravel. It turns out that Bennu’s surface is extremely strong, with no really friendly landing sites.
After spending much of the past two years re-evaluating the mission, the team decided to try “needle punching” through the rocky landscape at Nightingale and several other backup sampling sites. It is still possible that the surface may be too stony to obtain a good sample. If this turns out to be the case, the team can choose to try again on another site. Osiris-Rex is equipped with three nitrogen cans to shoot and disturb the surface, which means the team makes up to three sampling attempts.
Immediately after collecting his sample, Osiris-Rex will fire his pushers to pull away from Bennu. The spacecraft will continue to hover over Bennu until the end of 2020, before finally performing a take-off maneuver next year and embarking on a two-year voyage back to Earth.
On September 24, 2023, Osiris-Rex must discard his return return capsule, which will land in the Utah desert and be recovered for exploration.
Hasn’t this been done before?
Yes. Japanese spacecraft Hayabusa successfully returned small grains from asteroid 25143 Itokawa to Earth in 2010. Its successor, Hayabusa-2, successfullyand then took out some of the shrapnel. This sample is currently on its way back to Earth.
How can I watch?
Follow NASA’s live broadcast, which begins Tuesday at 2:00 p.m. PT. You can also follow Osiris-Rex’s Twitter feed to get the latest updates.