The collection of touch-and-go (TAG) samples of asteroid 101955 Bennu is scheduled for Tuesday 20 October at around 3:12 pm. PT. NASA will broadcast the TAG maneuver live on NASA TV and the agency’s website starting at 2:00 PM. PT Tuesday. Here’s everything you need to know about Osiris-Rex, Bennu, and how NASA plans to pickpocket an asteroid.
When did the mission start?
The Osiris-Rex 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, atop an Atlas V rocket from the United Launch Alliance, a joint venture of Lockheed Martin and Boeing. The spacecraft spent the next 26 months cruising to Bennu, officially arriving on December 3, 2018.
Since then, the mission team has spent nearly two years in orbit around the diamond-shaped space rock, detecting and mapping its surface to select the best sampling point. In recent months, rehearsals have started before the next sample-collection attempt, and now the team says it’s ready to play TAG with Bennu.
Bennu is what is called a “pile of rubble” asteroid, which means that it formed deep in the cosmic past as gravity slowly forced together the remains of an ancient collision. The result is a body shaped like something like a top with a diameter of about a third of a mile (500 meters) and a surface strewn with large rocks and boulders.
Bennu is thought to be a window into the solar system’s past: a pristine, carbon-rich body that carries the building blocks of planets and life. Some of these resources, such as water and metals, may also be worth mining in the future for use on Earth or in space exploration.
The asteroid has another feature that makes it particularly interesting for scientists and humans in general: it has the potential to impact Earth in the distant future. On NASA’s list of impact hazards, Bennu is ranked number 2. Current data shows dozens of potential impacts in the last quarter of the 22nd century, though all have only a slim chance of actually happening.
How will TAG work?
For anyone who has ever dabbled in robots or even participated in a robotics competition, the Osiris-Rex mission would seem to be the ultimate culmination of a young robotist’s dreams. The touch-and-go sampling procedure is a complex and high-risk activity that has been turning into a pivotal moment for years. If successful, it will play a role in history and our future in space.
The basic plan is that Osiris-Rex will land on Bennu on a rock. The van-sized spacecraft will have to tackle building-sized boulders around the landing area to land on a relatively clear space that’s only a few parking spaces large. However, a robotic sampling arm will be the only part of Osiris-Rex that actually lands on the surface. One of the three canisters of pressurized nitrogen will activate to raise a sample of dust and small rocks which can then be captured in the head of the boom collector to safely store it and return to Earth.
The descent to the surface of Bennu will take about four hours, about the time it takes for the asteroid to complete one full circle. After this slow approach, the actual TAG sample collection procedure takes considerably less than 16 seconds.
Preparation for TAG did not go exactly as planned. The mission organizers initially hoped that Bennu’s surface would have many potential landing spots covered mostly with fine materials comparable to sand or gravel. It turns out that Bennu’s surface is extremely bumpy with no real welcoming landing spots.
After spending much of the past two years re-evaluating the mission, the team decided to try to “thread the needle” through Nightingale’s boulder-filled landscape and a couple of other backup sample sites. It is still possible that the surface is too rocky to obtain a good sample. If this turns out to be the case, the team can choose to try again at another site. Osiris-Rex is equipped with three nitrogen cylinders to shoot and destroy the surface, meaning the team has up to three attempts to capture a champion.
Immediately after collecting his sample, Osiris-Rex will fire his thrusters to get away from Bennu. The spacecraft will continue to hover over Bennu for the remainder of 2020 before finally performing a departure maneuver next year and embarking on a two-year journey to Earth.
On September 24, 2023, Osiris-Rex is expected to throw overboard his champion return capsule, which will land in the Utah desert and be recovered for study.
Has this never been done before?
Yes. The Japanese probe Hayabusa successfully returned tiny grains of asteroid 25143 Itokawa to Earth in 2010. Its successor, Hayabusa-2, was successful.and then he recovered some splinters. That champion is currently on the way back to Earth.
How can I watch?
Follow the NASA live stream, which kicks off Tuesday at 2pm. PT. You can also follow the file Osiris-Rex Twitter feed to get the latest updates.