Source: NASA, [n.d.] [1]


The Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer, or OSIRIS-REx, is a NASA mission in which a spacecraft travels to a near-Earth asteroid (NEA), Bennu, a carbon-rich asteroid. It will gather at least a 2.1-ounce sample to bring back to Earth for study to help scientists investigate how planets formed, and how life began, as well as improve our understanding of asteroids that could impact Earth. The mission, launched September 8, 2016, is the first U.S. mission to return samples from an asteroid to Earth. OSIRIS-REx began the approach phase to the near Earth asteroid Bennu in August 2018. [1] OSIRIS-REx is the third mission in NASA's New Frontiers Program. [2]


Bennu is a carbonaceous asteroid whose regolith may record the earliest history of our solar system. The asteroid is about 1,900 feet in diameter (roughly the size of six football fields). Bennu was chosen for two major reasons: it is one of the most accessible carbonaceous NEAs; and, it has a relatively high probability of impacting Earth, a one in 1,800 chance of hitting Earth by the 22nd century. OSIRIS-REx will determine Bennu’s physical and chemical properties, which will be critical to know in the event of an impact mitigation mission. Scientists expect this asteroid, which has orbited the sun since the solar system’s infancy, could tell us more about the formative years of our solar system. [3]


OSIRIS-REx’s key science objectives include:

  • Return and analyze a sample of Bennu’s surface
  • Map the asteroid
  • Document the sample site
  • Measure the orbit deviation caused by non-gravitational forces (the Yarkovsky effect)
  • Compare observations at the asteroid to ground-based observations [4]


The OSIRIS-REx spacecraft was built by Lockheed Martin Space Systems.

  • Length:25 ft (6.2 m) with solar panels deployed
  • Width:8 ft (2.4 m) x 8 ft (2.4 m)
  • Height:33 ft (3.2 m)
  • TAGSAM Length:11 ft (3.4 m)
  • TAGSAM Head Width:12 in (30.5 cm) diameter
  • Dry Mass (unfueled):1,940 lbs (880 kg)
  • Wet Mass (fueled):4,650 lbs (2,110 kg)
  • Power:Two solar panels totaling 91 ft² (8.5 m²) generate between 1,226 and 3,000 watts, depending on the spacecraft’s distance from the Sun.
  • Payload:Five science instruments, the TAGSAM, and the SRC allow the spacecraft to gather data, collect a sample, and safely return it to Earth. [5]


OSIRIS-REx is outfitted with five instruments for remote sensing or scanning of the surface of Bennu to map and establish what makes up the asteroid, including the distribution of elements, minerals, and organic material. It has an additional instrument for sample collection. [6]

Source:  NASA/University of Arizona [7]

  • OSIRIS-REx Camera Suite (OCAMS) - consists of three cameras: PolyCam, MapCam, and SamCam to provide global image mapping of Bennu’s surface, and more detailed images of the selected and candidate sample sites.
  • OSIRIS-REx Laser Altimeter (OLA) - is a scanning LIDAR (Light Detection and Ranging) instrument that will provide high-resolution topographical information about Bennu during the mission.
  • OSIRIS-REx Visible and IR Spectrometer (OVIRS) – measures visible and infrared light from Bennu to provide spectral maps that identify mineral and organic material globally, and gathers local spectral information of candidate sample sites.
  • OSIRIS-REx Thermal Emission Spectrometer (OTES) - provides mineral and temperature information by collecting infrared (from 5.71–100 μ m) spectral data from Bennu. Thermal data from OTES allows scientists to determine the mineral composition and temperature distribution of Bennu for global maps and local candidate sample-site areas.
  • REgolith X-ray Imaging Spectrometer (REXIS) - a telescope that images the X-ray fluorescence line emission, allowing for mapping of the different elements present on Bennu’s surface.
  • Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – a simple sampler head with an articulated arm. Once the sampler head makes contact with the surface of Bennu, a burst of pure nitrogen gas will push surface regolith into the sampler’s chamber. [8]


The OSIRIS-REx team consists of university researchers, NASA personnel, and industry members. The mission's principal investigator is Dr. Dante Lauretta from the University of Arizona. The University of Arizona also leads the science team, and the mission’s science observation planning, and data processing. Overall mission management, systems engineering and safety and mission assurance for OSIRIS-Rex is provided by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Lockheed Martin Space Systems in Denver designed and built the spacecraft, and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. Collaborators from institutions around the US and other countries also contribute their expertise. For a full listing of team members and affiliations, click here. [9]


OSIRIS-REx launched from Cape Canaveral Air Force Station in Florida on an Atlas V 411 rocket on Sept. 8, 2016, and arrived at Bennu Dec. 3, 2018, when OSIRIS-REx transitioned from flying toward Bennu to operating around Bennu. The spacecraft’s detailed survey of Bennu is a process that will last over a year, and as part of it, OSIRIS-REx will map potential sample sites. While OSIRIS-REx is surveying and mapping Bennu, it will navigate in close proximity to the asteroid, and will ultimately touch the surface for five seconds to gather a sample of the asteroid. [10]

In March 2021, the window for departure from the asteroid will open, and OSIRIS-REx will begin its return journey to Earth, arriving two and a half years later in September 2023. The sample return capsule (SRC) will separate from the spacecraft and enter the Earth’s atmosphere. The capsule containing the sample will be collected at the Utah Test and Training Range. For two years after the sample return (from late 2023-2025), the science team will catalog the sample and conduct the analysis needed to meet the mission science goals. [11]


In October 2020, it was reported that the OSIRIS-REx spacecraft successfully touched the Bennu asteroid to collect dust and pebbles from the surface for delivery to Earth in 2023. 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. The sample collection event involved the extension of the sampling arm, known as the Touch-And-Go Sample Acquisition Mechanism (TAGSAM). Real-time data indicates the TAGSAM successfully contacted the surface, and fired a burst of nitrogen gas, which should have stirred up dust and pebbles on Bennu’s surface, some of which should have been captured in the TAGSAM sample collection head. All spacecraft telemetry data indicates the TAG event executed as expected. OSIRIS-REx engineers confirmed that shortly after the spacecraft made contact with the surface, it fired its thrusters, and safely backed away from Bennu. However, it will take about a week for the OSIRIS-REx team to confirm how much sample the spacecraft collected. If it turns out that the spacecraft did not collect enough sample, it will attempt another TAG maneuver on Jan. 12, 2021. In either case, the spacecraft will prepare for its departure from Bennu to begin its journey back to Earth in March 2021— the next time Bennu will be properly aligned with Earth for the most fuel-efficient return flight. [12]

Updated October 2020 by Diane M. Long