OSIRIS-REx

Firsts

• OSIRIS-REx will be the first U.S. mission to collect a sample from an asteroid and bring it to Earth

Key Dates

Sep 8, 2016: Launch

Sep 22, 2017: Earth flyby

Dec 3, 2018: Asteroid Bennu arrival

Sep 24, 2023: Sample capsule expected to return 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 is to collect a sample weighing 2.1 ounces (59.5 grams) from near-Earth asteroid 101955 Bennu (formerly known as 1999 RQ36) and then to bring the sample to Earth.

The mission, developed by scientists at the University of Arizona, will give scientists 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, 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, 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 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, 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, OSIRIS-REx sent back detailed images showing the asteroid’s shape and some surface features.

After arriving at Bennu Dec. 3, 2018, OSIRIS-REx began mapping the asteroid in detail, while the mission team searched for a safe site for sample collection. One of the biggest challenges is that Bennu has an extremely rocky surface and each boulder presents a danger to the spacecraft.

To expedite the sample site selection process, the team is asking citizen scientist volunteers to help develop a hazard map by counting boulders.

“For the safety of the spacecraft, the mission team needs a comprehensive catalog of all the boulders near the potential sample collection sites, and I invite members of the public to assist the OSIRIS-REx mission team in accomplishing this essential task,” said Dante Lauretta, OSIRIS-REx principal investigator.

To volunteer as a Bennu mapper, visit: Bennu.cosmoquest.org

After a site has been selected, the mission team will conduct several rehearsals without touching the asteroid. Then in July 2020, the sampling maneuver is scheduled to begin.

OSIRIS-REx won’t land on Bennu to gather the sample, but it will get very close. After descending toward the surface, a process that will take several hours, the spacecraft’s robotic arm, the TAGSAM instrument, will actually make contact with the asteroid. TAGSAM will release a burst of nitrogen gas to kick up regolith particles (loose dust and rocks) from the surface. The sampler head at the end of the robotic arm will collect the regolith.

OSIRIS-REx has enough nitrogen gas for three sampling attempts. If the first attempt is successful, the team will not try again to avoid putting the spacecraft at risk. If it’s not successful, the spacecraft can repeat the sampling maneuver up to two more times.

Once a sample has been collected, the TAGSAM sampler head will be stowed in the sample return capsule. OSIRIS-REx will then wait for the proper alignment of Bennu and Earth in their orbits before it begins its return trip.

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.