OSIRIS-REx

Firsts

• OSIRIS-REx is the first U.S. mission to collect a sample from an asteroid.

Key Dates

Sep 8, 2016: Launch

Sep 22, 2017: Earth flyby

Dec 3, 2018: Asteroid Bennu arrival

Oct. 20, 2020: OSIRIS-REx successfully collects a sample from Bennu

April 7, 2021: OSIRIS-REx completes its last flyover of Bennu

May 10, 2021: OSIRIS-REx is scheduled to begin its journey back to Earth

Sep 24, 2023: Sample capsule expected to be delivered to Earth

In Depth: OSIRIS-REx

OSIRIS-REx is the third major planetary science mission for NASA’s New Frontiers Program (after New Horizons launched in 2006 and Juno launched in 2011).

OSIRIS-REx is an acronym for "Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer." The goal of the mission – collect a sample weighing at least 2.1 ounces (59.5 grams) from near-Earth asteroid 101955 Bennu (formerly known as 1999 RQ36) and then bring the sample to Earth.

The mission, developed by scientists at the University of Arizona, will give us more information about how the early solar system formed and about how life began. It will also help us better understand asteroids that could impact Earth in the future.

About 55 minutes after launch on Sept. 8, 2016, from Cape Canaveral, Florida, and after a boost by the Centaur upper stage, OSIRIS-REx separated from its Atlas V rocket and deployed its solar arrays.

At 17:30 UT Sept. 9, 2016, the spacecraft crossed the orbital path of the Moon at a range of about 240,200 miles (386,500 kilometers). Three days later, it was in orbit around the Sun. Beginning Sept. 19, 2016, the mission team activated all of its scientific instruments.

The spacecraft’s trajectory correction maneuver (TCM) thrusters were fired for 12 seconds for the first time on Oct. 7, 2016, for a course correction. The spacecraft also carries three other sets of thrusters—the attitude control system (ACS), the main engine (ME), and low thrust reaction engine assembly (LTR) thrusters—thus providing significant redundancy for maneuvers.

On Dec. 28, 2016, the spacecraft conducted its first deep-space maneuver (DSM-1), firing the main engine to position it properly for an Earth gravity-assist encounter in late 2017.

A second firing, the first to use the spacecraft’s attitude control system (ACS) thrusters, on Aug. 25, 2017, further sharpened its trajectory by changing the velocity by about 19 inches (47.9 centimeters) per second.

About a month later, on Sept. 22, 2017, OSIRIS-REx, passed Earth at a range of about 10,710 miles (17,237 kilometers) as part of a gravity-assist maneuver that tilted its orbit to match that of Bennu. During the encounter, the spacecraft took several high-resolution pictures of both Earth and the Moon.

The spacecraft got its first glimpse of Bennu in August 2018, sending back a grainy image taken at a distance of about 1.4 million miles (2.3 million kilometers). In early November 2018, OSIRIS-REx sent back detailed images showing the asteroid’s shape and some surface features.

After arriving at Bennu on Dec. 3, 2018, OSIRIS-REx mapped the asteroid in detail while the mission team searched for a safe sample collection site. One of the biggest challenges was that Bennu has an extremely rocky surface with hazardous boulders.

After a year, the mission team selected a sample site called “Nightingale” located in a northern crater 460 feet (140 meters) wide. The crater is thought to be relatively young, and the regolith, or rocks and dust, is freshly exposed. This means the site would likely allow for a pristine sample of the asteroid, giving the team insight into Bennu’s history.

On Oct. 20, 2020, OSIRIS-REx unfurled its robotic arm and, in a first for NASA, briefly touched down on asteroid Bennu to collect dust and pebbles from its surface in a maneuver known as “Touch-And-Go” or TAG.

Two days later, the mission team received images that confirmed the spacecraft had collected more than enough material to meet one of its main mission requirements – acquiring at least 2 ounces (60 grams) of Bennu’s surface material. On Oct. 28, 2020, the mission team sent commands to the spacecraft, instructing it to close the Sample Return Capsule – marking the end of one of the most challenging phases of the mission.

On April 7, 2021, OSIRIS-REx completed its last flyover of Bennu around 6 a.m. EDT and started slowly drifting away from the asteroid. During the flyby, OSIRIS-REx imaged Bennu for 5.9 hours, covering more than a full rotation of the asteroid. It flew within 2.1 miles (3.5 kilometers) of Bennu's surface – the closest since the TAG sample collection event.

OSIRIS-REx will remain in the vicinity of Bennu until May 10, 2021, when it will fire its thrusters and begin its two-year cruise home.

On Sept. 24, 2023, the OSIRIS-REx spacecraft will approach Earth, but it won’t land. Instead, it will release the capsule carrying the asteroid sample for a parachute landing. The main spacecraft will continue on to orbit the Sun.

The sample capsule will deploy its parachute at an altitude of about 1.9 miles (3 kilometers), bringing it in for a soft landing at the Utah Test and Training Range about 80 miles (130 kilometers) west of Salt Lake City, Utah.

The capsule will be sent to Johnson Space Center in Houston, Texas, where scientists at the Astromaterials Acquisition and Curation Office will catalog it and set aside portions of the sample for partners in the Japanese and Canadian space agencies.

After about six months, NASA will distribute parts of the sample to research groups around the world. A portion of the sample will also be stored at a secure location in New Mexico as a sort of insurance policy.

As for the spacecraft, depending on the amount of fuel remaining and other factors, OSIRIS-REx may be reassigned to other exploration duties, but it will no longer be capable of collecting samples and delivering them to Earth.

Additional Resources

• NASA: OSIRIS-REx
• University of Arizona: OSIRIS-REx
• National Space Science Data Center Master Catalog: OSIRIS-REx

Key Source

Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.