Overall management, engineering, and navigation for the OSIRIS missions are provided by
NASA Goddard Space Flight Center, while the
University of Arizona Lunar and Planetary Laboratory provides principal science operations.
Lockheed Martin Space Systems built the spacecraft and provides mission operations. After traveling for approximately two years, the spacecraft
rendezvoused with asteroid
101955 Bennu in December 2018, and began 505 days of surface mapping at a distance of approximately . Then a close approach (without landing) was carried out to allow extension of a robotic arm to gather the sample. Following the successful collection of material (), the sample was returned to Earth in a capsule similar to that which returned the samples of Comet
81P/Wild on the space probe
Stardust. The return trip to Earth was shorter than the outbound trip. The capsule landed by parachute at the
Utah Test and Training Range on 24 September 2023 and was transported to the
Johnson Space Center for processing in a dedicated research facility. OSIRIS-REx separated from the launch vehicle 55 minutes after ignition.
Cruise phase OSIRIS-REx entered the cruise phase shortly after separation from the launch vehicle, following successful solar panel deployment, propulsion system initiation, and establishment of a communication link with Earth. On 28 December 2016, the spacecraft successfully performed its first deep space maneuver to change its velocity by using of fuel. An additional, smaller firing of its thrusters on 18 January 2017 further refined its course for an Earth
gravity assist on 22 September 2017. as it closely resembled the operation required as the spacecraft approached Bennu, searching for natural satellites and other potential hazards. On 12 February 2017, while from
Jupiter, the PolyCam instrument aboard OSIRIS-REx successfully imaged the giant planet and three of its moons,
Callisto,
Io, and
Ganymede. OSIRIS-REx flew by Earth on 22 September 2017.
Arrival and survey On 3 December 2018, NASA confirmed that OSIRIS-REx had matched the speed and orbit of Bennu at a distance of about , effectively reaching the asteroid. OSIRIS-REx performed closer passes of the Bennu surface, initially at about through December to further refine the shape and orbit of Bennu. Preliminary spectroscopic surveys of the asteroid's surface by the OSIRIS-REx spacecraft detected the presence of
hydrated minerals in the form of
clay. While researchers suspect that Bennu was too small to host water, the hydroxyl groups may have come from water present in its parent body before Bennu split off. OSIRIS-REx entered orbit around Bennu on 31 December 2018 at about to start its extensive remote mapping and sensing campaign for the selection of a sample site. This is the closest distance that any spacecraft has orbited a celestial object, closer than the
Rosetta orbit of comet
67P/Churyumov–Gerasimenko at . At this altitude, it took the spacecraft 62 hours to orbit Bennu. At the end of its detailed survey, the spacecraft entered a closer orbit with a radius of .
Sample acquisition Procedure Rehearsals were performed before sampling, during which the solar arrays were raised into a Y-shaped configuration to minimize the chance of dust accumulation during contact and provide more ground clearance in case the spacecraft tipped over (up to 45°) during contact. Upon surface contact by the TAGSAM instrument, a burst of
nitrogen gas was released to blow
regolith particles smaller than into the sampler head at the end of the robotic arm. A five-second timer limited the collection time to mitigate the chance of a collision, and the probe then executed a back-away maneuver to depart safely. In addition to the bulk sampling mechanism, contact pads on the end of the sampling head made of tiny stainless steel loops (
Velcro) passively collected dust grains smaller than .
Operations NASA selected the final four candidate sample sites in August 2019, named Nightingale, Kingfisher, Osprey, and Sandpiper. On 12 December 2019, they announced that Nightingale had been selected as the primary sample site and Osprey was selected as the backup site. Both were within craters, with Nightingale near Bennu's north pole while Osprey was near the equator. NASA planned to perform the first sampling in late August 2020; NASA's originally planned Touch-and-Go (TAG) sample collection was scheduled for 25 August 2020, but was rescheduled for 20 October 2020, at 22:13 UTC. On 15 April 2020, the first sample collection rehearsal was successfully performed at the Nightingale sample site. The exercise took OSIRIS-REx as close as from the surface before performing a back-away burn. A second rehearsal was successfully completed on 11 August 2020, bringing OSIRIS-REx down to from the surface. This was the final rehearsal before the sample collection scheduled for 20 October 2020, at 22:13 UTC. At 22:13 UTC, on October 20, 2020, OSIRIS-REx successfully touched down on Bennu at a distance of from Earth. NASA confirmed via images taken during sampling that the sampler had made contact. The spacecraft touched down within of the target location. A sample of the asteroid which was estimated to weigh at least was collected by OSIRIS-REx following the touch down. When the head was seated into the Sample-Return Capsule's capture ring on 28 October 2020, the spacecraft performed a "backout check", which commanded the TAGSAM arm to back out of the capsule. This maneuver is designed to tug on the collector head and ensure that the latches – which keep the collector head in place – are well secured. Following the test, the mission team received telemetry confirming that the head was properly secured in the Sample-Return Capsule. Thereafter, on 28 October 2020, two mechanical parts on the TAGSAM arm were disconnected – these are the tube that carried the nitrogen gas to the TAGSAM head during sample collection and the TAGSAM arm itself. Over the next several hours, the mission team commanded the spacecraft to cut the tube that stirred up the sample through the TAGSAM head during sample collection, and separate the collector head from the TAGSAM arm. Once the team confirmed these activities were done, it commanded the spacecraft on 28 October 2020, to close and seal the Sample-Return Capsule, the final step of the sample stowage process of Bennu's samples. To seal the SRC, the spacecraft closed the lid and then secured two internal latches. On inspecting images, it was observed that a few particles had escaped from the collector head during the stowage procedure, but it was confirmed that no particles would hinder the stowage process, since the team was confident that a plentiful amount of material remained inside of the head, more than the needed, that is, . The sample of Bennu was safely stored and ready for its journey to Earth. With the collector head secure inside the SRC, pieces of the sample would no longer be lost.
Sample return On 7 April 2021, OSIRIS-REx completed its final flyover of Bennu and began drifting away from the asteroid. On 10 May 2021, the spacecraft departed the vicinity of Bennu and began its two-year journey to Earth with the asteroid sample. On 24 September 2023, at 4:42 a.m.
MDT, at a distance of from Earth, it ejected the sample return capsule, which re-entered
the atmosphere at . Due to a mistake in wiring, the drogue parachute did not deploy as planned at 100,000 feet (30,400 meters). However, the main parachute was released when the spacecraft reached about 9,000 feet (2,700 meters), and it survived deployment despite higher than anticipated speeds. The main spacecraft maneuvered to a trajectory away from Earth for its extended mission to
Apophis in 2029 called
OSIRIS-APEX. At 10:15 a.m. MDT, the capsule was taken from the landing site by helicopter. The sample will be
analyzed at NASA's
Astromaterials Research and Exploration Science Directorate (ARES) and at Japan's
Extraterrestrial Sample Curation Center. Asteroid sample material requests will be considered and distributed to organizations worldwide by ARES. On 11 October 2023, the recovered capsule was opened to reveal a "first look" at the asteroid sample contents. Further looks were reported on 13 December 2023 and revealed
organic molecules and unknown materials that require study to determine their composition. Some damaged fasteners prevented immediate opening, but, after three months, on 13 January 2024, NASA reported fully opening the recovered container. In total, of asteroidal material was recovered from the sample container. The samples became available to the world’s scientists for research by request on 1 April 2024. On 15 May 2024, an overview of preliminary analytical studies on the returned samples was reported. In January 2025, NASA revealed that while the samples did not show evidence of life, their contents suggest that the conditions necessary for the emergence of life were likely widespread in the early solar system. The amount of ammonia, a volatile substance, in the samples indicates that Bennu emerged from the colder, outer regions of space. ==Extended mission OSIRIS-APEX==