OSIRIS-REx

NASA’s OSIRIS-REx, currently orbiting asteroid 101955 Bennu, will be the first U.S. mission to bring an asteroid sample to Earth.

• OSIRIS-REx will spend two years mapping Bennu, a potentially hazardous asteroid that could one day threaten Earth.
• The maps will be used to select the site where the spacecraft will use its robotic arm to collect regolith, or loose dust and broken rocks from the surface of the asteroid. The sample will weigh at least 2.1 ounces (59.5 grams)
• The sample will be stored on the spacecraft and returned to Earth in September 2023.

Firsts

OSIRIS-REx will be the first U.S. mission to collect samples from an asteroid and bring them to Earth.

Key Dates

Sept. 8, 2016 | 23:05 UT: Launch

Sept. 22, 2017 at 16:52 UT: Earth Flyby

Dec. 3, 2018: Asteroid Bennu Arrival

Sept. 24, 2023: Sample Return to Earth

In Depth

Objective(s): asteroid sample return

Spacecraft Mass: 4,652 pounds (2,110 kilograms)

Mission Design and Management: NASA GSFC / University of Arizona

Scientific Instruments:

1. Camera Suite (PolyCam, MapCam, SamCam) (OCAMS OSIRIS-REx)

2. Laser Altimeter (OLA OSIRIS-REx)

3. Visible and IR Spectrometer (OVIRS OSIRIS-REx)

4. Thermal Emission Spectrometer (OTES OSIRIS-REx)

5. Regolith X-Ray Imaging Spectrometer (REXIS OSIRIS-REx)

6. Touch-And-Go Sample Acquisition Mechanism (TAGSAM)

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, and 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, 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 on September 9, the spacecraft crossed the orbital path of the moon at a range of 240,161 miles (386,500 kilometers). Three days later, it was in orbit around the sun. Beginning September 19, the mission team activated all of its scientific instruments.

The spacecraft’s larger Trajectory Correction Maneuver (TCM) thrusters were fired (for 12 seconds) for the first time on October 7 for a mid-course correction. The spacecraft also carries three other sets of thrusters—the Attitude Control System (ACS), a Main Engine (ME), and Low Thrust Reaction Engine Assembly (LTR) thrusters -- thus providing significant redundancy for maneuvers.

On December 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 August 25, 2017, further sharpened its trajectory by changing the velocity by 47.9 centimeters/second. About a month later, on September 22, OSIRIS-REx passed by Earth at a range of 10,711 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 1.4 million miles (2,253,076 kilometers). In early November, OSIRIS-REx sent back detailed images showing the asteroid’s shape and some surface features.

After arriving at Bennu in December 2018, OSIRIS-REx will begin a series of maneuvers around the asteroid, culminating in reconnaissance flyovers at about 800 feet (240 meters) from the surface to allow the spacecraft’s instruments to map Bennu’s surface. The maps will be used to help select the site where the spacecraft will collect samples in July 2020.

After a site has been selected, the mission team will conduct several rehearsals without touching the asteroid.

OSIRIS-REx won’t land on Bennu, 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.

After the sample has been safely stowed, OSIRIS-REx will wait for the proper alignment of Bennu and the Earth in their orbits before beginning its 2.5-year return journey home in March 2021.

On September 24, 2023, OSIRIS-REx will approach Earth, but it won’t land. Instead, it will release the capsule carrying the asteroid sample for a parachute landing and then continue on to orbit the sun.

The sample capsule will hit the Earth’s atmosphere traveling at more than 27,000 miles per hour (12.2 kilometers per second). It 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 (UTTR), located about 80 miles 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

Source

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