NASA’s OSIRIS-REx Spacecraft Successfully Touches Asteroid and Collects Samples
NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft unfurled its robotic arm on October 20, 2020, and in a first for the agency, briefly touched an asteroid to collect dust and pebbles from the surface for delivery to Earth in 2023.
This well-preserved, ancient asteroid, known as Bennu, is currently more than 321 million kilometers (200 million miles) from Earth. Bennu offers scientists a window into the early solar system as it was first taking shape billions of years ago and flinging ingredients that could have helped seed life on Earth.
“This amazing first for NASA demonstrates how an incredible team from across the country came together and persevered through incredible challenges to expand the boundaries of knowledge,” said NASA Administrator Jim Bridenstine. “Our industry, academic, and international partners have made it possible to hold a piece of the most ancient solar system in our hands.”
At 1:50 p.m. EDT on October 20, OSIRIS-REx fired its thrusters to nudge itself out of orbit around Bennu. It extended the shoulder, then elbow, then wrist of its 3.35-meter (11-foot) sampling arm, known as the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), and transited across Bennu while descending about 805 meters (2641 feet) toward the surface. After a four-hour descent, at an altitude of approximately 125 meters (410 feet), the spacecraft executed the “Checkpoint” burn, the first of two maneuvers to allow it to precisely target the sample collection site, known as “Nightingale.”
Ten minutes later, the spacecraft fired its thrusters for the second “Matchpoint” burn to slow its descent and match the asteroid’s rotation at the time of contact. It then continued a treacherous, 11-minute coast past a boulder the size of a two-story building, nicknamed “Mount Doom,” to touch down in a clear spot in a crater on Bennu’s northern hemisphere. The size of a small parking lot, the Nightingale site is one of the few relatively clear spots on this unexpectedly boulder-covered space rock.
“This was an incredible feat — and today, we’ve advanced both science and engineering and our prospects for future missions to study these mysterious ancient storytellers of the solar system,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at the agency’s headquarters in Washington.
Two days after touching down on asteroid Bennu, NASA’s OSIRIS-REx mission team received images that confirmed the spacecraft collected more than enough material to meet one of its main mission requirements — acquiring at least 60 grams (2 ounces) of the asteroid’s surface material.
The spacecraft captured images of the sample collector head as it moved through several different positions. In reviewing these images, the OSIRIS-REx team noticed both that the head appeared to be full of asteroid particles and that some of these particles appeared to be escaping slowly from the sample collector, called the TAGSAM head. They suspect bits of material are passed through small gaps where a mylar flap — the collector’s “lid” — was slightly wedged open by larger rocks.
“Bennu continues to surprise us with great science and also throwing a few curveballs,” said Thomas Zurbuchen, NASA’s associate administrator for science at the agency’s headquarters in Washington. “And although we may have to move more quickly to stow the sample, it’s not a bad problem to have. We are so excited to see what appears to be an abundant sample that will inspire science for decades beyond this historic moment.”
The team believes it has collected a sufficient sample and is on a path to stow the sample as quickly as possible. They came to this conclusion after comparing images of the empty collector head with images of the TAGSAM head after the sample collection event.
The images also show that any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss. To preserve the remaining material, the mission team decided to forego the sample mass measurement activity and canceled a braking burn to minimize any acceleration to the spacecraft.
From here, the OSIRIS-Rex team will focus on stowing the sample in the sample return capsule (SRC), where any loose material will be kept safe during the spacecraft’s journey back to Earth.
“We are working to keep up with our own success here, and my job is to safely return as large a sample of Bennu as possible,” said Dante Lauretta, OSIRIS-REx Principal Investigator at the University of Arizona in Tucson, who leads the science team and the mission’s science observation planning and data processing. “The loss of mass is of concern to me, so I’m strongly encouraging the team to stow this precious sample as quickly as possible.”
The TAGSAM head performed the sampling event in optimal conditions. Newly available analyses show that the collector’s head was flush with Bennu’s surface when it made contact and when the nitrogen gas bottle was fired to stir surface material. It also penetrated several centimeters into the asteroid’s surface material. All data so far suggest that the collector’s head is holding much more than 60 grams (2 ounces) of regolith.
OSIRIS-REx remains in good health, and the mission team is finalizing a timeline for sample storage. An update will be provided once a decision is made on the sample storage timing and procedures.
OSIRIS-REx launched from Cape Canaveral Air Force Station in Florida on September 8, 2016. It arrived at Bennu on December 3, 2018, and began orbiting the asteroid for the first time on December 31, 2018. The spacecraft is scheduled to return to Earth on September 24, 2023, when it will parachute the SRC into Utah’s West Desert, where scientists will be waiting to collect it.
For more information about the OSIRIS-REx mission, visit https://www.asteroidmission.org/.