OSIRIS-REx
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OSIRIS-REx was a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
asteroid-study and
sample-return mission A sample-return mission is a spacecraft mission to collect and return samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as lo ...
that visited and collected samples from
101955 Bennu 101955 Bennu ( provisional designation ) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the second hig ...
, a
carbonaceous Carbonaceous refers to something relating to, containing, or composed of carbon. It is a descriptor used for the attribute of any substance rich in carbon. Particularly, ''carbonaceous hydrocarbons'' are very unsaturated, high- molecular-weight h ...
near-Earth asteroid A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit aro ...
. The material, returned in September 2023, is expected to enable scientists to learn more about the
formation and evolution of the Solar System There is evidence that the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while ...
, its initial stages of planet formation, and the source of
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s that led to the formation of life on Earth. Following the completion of the primary OSIRIS-REx (Regolith Explorer) mission, the spacecraft is planned to conduct a flyby of asteroid
99942 Apophis 99942 Apophis ( provisional designation ) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size, that caused a brief period of concern in December 2004 when initial observatio ...
, renamed as OSIRIS-APEX (Apophis Explorer). OSIRIS-REx was launched on 8 September 2016, flew past Earth on 22 September 2017, and rendezvoused with Bennu on 3 December 2018. It spent the next two years analyzing the surface to find a suitable site from which to extract a sample. On 20 October 2020, OSIRIS-REx touched down on Bennu and successfully collected a sample. OSIRIS-REx left Bennu on 10 May 2021 and returned its sample to Earth on 24 September 2023, subsequently starting its extended mission to study
99942 Apophis 99942 Apophis ( provisional designation ) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size, that caused a brief period of concern in December 2004 when initial observatio ...
, where it will arrive in April 2029. Bennu was chosen as the target of study because it is a "
time capsule A time capsule is a historic treasure trove, cache of goods or information, usually intended as a deliberate method of communication with future people, and to help future archaeologists, anthropologists, or historians. The preservation of holy ...
" from the birth of the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
. Bennu has a very dark surface and is classified as a
B-type asteroid B-type asteroids are a relatively uncommon type of carbonaceous asteroid, falling into the wider C-type asteroid#C-group asteroids, C-group; the 'B' indicates these objects are spectrally blue. In the asteroid population, B-class objects can be f ...
, a sub-type of the carbonaceous
C-type asteroid C-type (carbonaceous ) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...
s. Such asteroids are considered primitive, having undergone little geological change from their time of formation. In particular, Bennu was selected because of the availability of pristine
carbonaceous Carbonaceous refers to something relating to, containing, or composed of carbon. It is a descriptor used for the attribute of any substance rich in carbon. Particularly, ''carbonaceous hydrocarbons'' are very unsaturated, high- molecular-weight h ...
material, a key element in
organic molecules Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-cont ...
necessary for life as well as representative of matter from before the formation of Earth. Organic molecules, such as
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
s, have previously been found in meteorite and comet samples, indicating that some ingredients necessary for life can be naturally synthesized in outer space. The cost of the OSIRIS-REx mission is approximately US$800 million, not including the
Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to launch payloads for ...
launch vehicle, which is about US$183.5 million. The OSIRIS-APEX extended mission costs an additional US$200 million. It is the third planetary science mission selected in the
New Frontiers program The New Frontiers program is a series of space exploration missions being conducted by NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the ...
, after ''Juno'' and ''
New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...
''. The principal investigator is Dante Lauretta from the
University of Arizona The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...
, having taken over in 2011 after the original PI Michael Julian Drake died four months after the mission won approval from NASA. OSIRIS-REx was the first United States spacecraft to return samples from an asteroid. Previous asteroid returns include the Japanese probes ''
Hayabusa was a robotic spacecraft developed by the Japan Aerospace Exploration Agency (JAXA) to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. ''Hayabusa'', formerly known as MUSES-C ...
'', which visited
25143 Itokawa 25143 Itokawa (provisional designation ) is a sub-kilometer near-Earth object of the Apollo group and also a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo ...
in 2010, and '' Hayabusa2'', which visited 162173 Ryugu in June 2018.


Mission

Overall management, engineering, and navigation for the OSIRIS missions are provided by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...
, while the
University of Arizona The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...
Lunar and Planetary Laboratory provides principal science operations.
Lockheed Martin Space Systems Lockheed Martin Space is one of the four major business divisions of Lockheed Martin. It has its headquarters in Littleton, Colorado, with additional sites in Valley Forge, Pennsylvania; Sunnyvale, California; Santa Cruz, California; Huntsville ...
built the spacecraft and provides mission operations. The science team includes members from the United States, Canada, France, Germany, the United Kingdom, and Italy. After traveling for approximately two years, the spacecraft rendezvoused with asteroid
101955 Bennu 101955 Bennu ( provisional designation ) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the second hig ...
in December 2018, and began 505 days of surface mapping at a distance of approximately . Results of that mapping were used by the mission team to select the site from which to take a sample of at least of material of the asteroid's surface. 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 (121.6 grams), 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 The Utah Test and Training Range (UTTR) is a Department of Defense military testing and training area located in Utah's West Desert, approximately west of Salt Lake City, Utah. UTTR is currently the largest contiguous block of over-land superso ...
on September 24, 2023 and was transported to the
Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...
for processing in a dedicated research facility. File:Asteroid-Bennu-OSIRIS-RExArrival-GifAnimation-20181203.gif, Asteroid Bennu, imaged by the OSIRIS-REx probe, 3 December 2018 File:To Bennu and Back.webm, OSIRIS-REx mission overview video File:Liftoff-of-OSIRIS-REx.ogg, OSIRIS-REx launch


Launch

The launch was on 8 September 2016 at 23:05
UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...
on a
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from
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, Space Launch Complex 41. The 411 rocket configuration consists of a
RD-180 The RD-180 () is a rocket engine that was designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a RP-1/ LOX mixture. The RD-180 is derived from the RD-170 line of rocket engines, which were use ...
powered first stage with a single AJ-60A solid fuel booster, and a
Centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...
upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...
. OSIRIS-REx separated from the launch vehicle 55 minutes after ignition. The launch was declared "exactly perfect" by the mission's principal investigator, with no anomalies before or during launch.


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. Its hyperbolic escape speed from Earth was about . 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 A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby (spaceflight), flyby which makes use of the relative movement (e.g. orbit around the Sun) and gra ...
on 22 September 2017. The cruise phase lasted until its encounter with Bennu in December 2018, after which it entered its science and sample collection phase. During its cruise phase, OSIRIS-REx was used to search for a class of
near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...
s known as Earth-Trojan asteroids as it passed through Sun–Earth
Lagrange point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the gravitational influence of two massive orbiting bodies. Mathematically, this involves t ...
. Between 9 and 20 February 2017, the OSIRIS-REx team used the spacecraft's MapCam camera to search for the objects, taking about 135 survey images each day for processing by scientists at the University of Arizona. The search was beneficial even though no new trojans were found, 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 Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, the PolyCam instrument aboard OSIRIS-REx successfully imaged the giant planet and three of its moons,
Callisto CALLISTO (''Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations'') is a reusable VTVL Prototype, demonstrator propelled by a small 40 kN Japanese LOX-LH2 rocket engine. It is being developed jointly by the CNES, French ...
, 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 Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...
. 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 67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C–G) is a Jupiter-family comet. It is originally from the Kuiper belt and has an orbital period of 6.45 years as of 2012, a rotation period of approximately 12.4 hours, and a maximum velo ...
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. The descent was very slow, minimizing thruster firings prior to contact to reduce the likelihood of asteroid surface contamination by unreacted
hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...
propellant. On 20 October 2020, contact with the surface of Bennu was detected using accelerometers, and the impact force was dissipated by a spring in the TAGSAM arm. Upon surface contact by the TAGSAM instrument, a burst of
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
gas was released to blow
regolith Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...
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. The plan was then for OSIRIS-REx to perform a braking maneuver a few days later to halt the drift away from the asteroid in case it was necessary to return for another sampling attempt. It would then take images of the TAGSAM head to verify a sample had been acquired. If a sample was acquired, the spacecraft would rotate about the short axis of the sample arm to determine sample mass by measuring momentum of inertia and determine if it was in excess of the required . Both the braking and rotation maneuvers were canceled when images of the sample container clearly showed a large excess of material was collected, some of which was able to escape through the container's seal because some material had jammed the mechanism open. The collected material was scheduled for immediate storage in the Sample-Return Capsule. On 28 October 2020, the sample collector head was secured in the return capsule. Following the separation of the head from the collector arm, the arm was retracted into its launch configuration, and the Sample-Return Capsule lid was closed and latched preparing to return to Earth. In addition to the bulk sampling mechanism, contact pads on the end of the sampling head made of tiny stainless steel loops (
Velcro Velcro IP Holdings LLC, trading as Velcro Companies and commonly referred to as Velcro (pronounced ), is a British privately held company, founded by Swiss electrical engineer George de Mestral in the 1950s. It is the original manufacturer of ho ...
) 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 , on 20 October 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. After imaging the TAGSAM head, NASA concluded that there were rocks wedged in the mylar flap meant to keep the sample inside, causing the sample to slowly escape into space. In order to prevent further loss of the sample through the flaps, NASA canceled the previously planned spinning maneuver meant to determine the mass of the sample as well as a navigational braking maneuver, and decided to stow the sample on 27 October 2020 rather than 2 November 2020 as originally planned, which was completed successfully. The collector head was observed hovering over the Sample Return Capsule (SRC) after the TAGSAM arm moved it into the proper position for capture, and the collector head was later secured onto the capture ring in the SRC. 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 ( UTC-06:00), 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. About 8:52 a.m. MDT the capsule landed at at the
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, one minute earlier than predicted. 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 (UTC-06:00), 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 molecule Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-cont ...
s 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 in an early solar system, their contents suggest that the conditions necessary for the emergence of life were likely widespread across it. These findings have prompted scientists to wonder why life did not emerge from Bennu. Further, they theorize that the amount of ammonia, which is a volatile substance, in the samples indicates that Bennu emerged from the colder, outer regions of space. In January 2025, it was reported that a wide range of carbon- and nitrogen-rich organic compounds have been identified in samples returned from Bennu, including 14 of the 20 amino acids that make up proteins in terrestrial organisms, as well as all four nucleobases (adenine, thymine, cytosine and guanine) that are the essential building blocks of DNA and RNA. The samples contain a nearly equal mix of left-handed (L) and right-handed (D) amino acids, raising questions about whether asteroids like Bennu helped shape Earth's biochemistry.


Extended mission OSIRIS-APEX

On 25 April 2022, NASA confirmed that the mission would be extended. After dropping off its sample to Earth on 24 September 2023, the mission became ''OSIRIS-APEX'' ('APophis EXplorer'). As the new name suggests, its next target will be the
near-Earth asteroid A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit aro ...
(and
potentially hazardous object A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. Th ...
)
99942 Apophis 99942 Apophis ( provisional designation ) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size, that caused a brief period of concern in December 2004 when initial observatio ...
. Apophis will make an extremely close pass to the Earth on 13 April 2029, although there is no chance for an impact during this or any subsequent flybys in the near future. Observations of Apophis will commence on 8 April 2029, and a few days later, on 21 April, OSIRIS-APEX is planned to rendezvous with the asteroid. OSIRIS-APEX will orbit Apophis for around 18 months in a regime similar to that at Bennu. The spacecraft will perform a maneuver, similar to sample collection at Bennu, by using its thrusters to disturb Apophis's surface, in order to expose and spectrally study the subsurface and the material beneath it.


Name

OSIRIS-REx and OSIRIS-APEX are acronyms, and each letter or combination of letters relates to part of the respective projects: *O – Origins *SI – Spectral Interpretation *RI – Resource Identification *S – Security *REx – Regolith Explorer *APEX – Apophis Explorer Each of these words was chosen to represent an aspect of this mission. For example, the S, for security means the security of Earth from impact by hazardous
near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...
s (NEOs). Specifically it refers to better understanding the Yarkovsky effect, which can alter the trajectories of orbiting bodies. Regolith Explorer means that the mission will study the texture, morphology,
geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...
, and spectral properties of the regolith of asteroid Bennu while Apophis Explorer corresponds to the study of Apophis asteroid. When its heritage concept was proposed in the
Discovery Program The Discovery Program is a series of Solar System exploration missions funded by the U.S. National Aeronautics and Space Administration (NASA) through its Planetary Missions Program Office. The cost of each mission is capped at a lower level t ...
in 2004, it was called only OSIRIS, with REx for "Regolith Explorer" used descriptively rather than as part of the name. The asteroid for the second mission is named after the
ancient Egyptian Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower E ...
god Apophis, who was associated with chaos and destruction. The mission name itself was a reference to the god
Osiris Osiris (, from Egyptian ''wikt:wsjr, wsjr'') was the ancient Egyptian deities, god of fertility, agriculture, the Ancient Egyptian religion#Afterlife, afterlife, the dead, resurrection, life, and vegetation in ancient Egyptian religion. He was ...
. Dante Lauretta, deputy PI of the mission, was called "a mythology buff" by the mission PI Michael Drake: "he was doodling on a pad and trying to capture the principal themes of what we are trying to do with this mission—study life origins, identify resources, planetary security in the form of asteroid deflection—and he realized he got the name of Osiris out of that, an ancient god of Egypt who may have been one of the first pharaohs."


Science objectives

The science objectives of the mission are: * Return and analyze a sample of pristine carbonaceous asteroid regolith in an amount sufficient to study the nature, history, and distribution of its constituent minerals and
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s * Map the global properties, chemistry, and mineralogy of a primitive carbonaceous asteroid to characterize its geologic and dynamic history and provide context for the returned samples * Document the texture, morphology,
geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...
, and spectral properties of the
regolith Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...
at the sampling site ''in situ'' at scales down to millimeters * Measure the Yarkovsky effect (a thermal force on the object) on a potentially hazardous asteroid and constrain the asteroid properties that contribute to this effect * Characterize the integrated global properties of a primitive carbonaceous asteroid to allow for direct comparison with ground-based telescopic data of the entire asteroid population Telescopic observations have helped define the orbit of
101955 Bennu 101955 Bennu ( provisional designation ) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the second hig ...
, a
near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...
(NEO) with a mean diameter in the range of . It completes an orbit of the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
every 436.604 days (1.2 years). This orbit takes it close to the Earth every six years. Although the orbit is reasonably well known, scientists continue to refine it. It is critical to know the orbit of Bennu because recent calculations produced a cumulative probability of 1 in 1410 (or 0.071%) of impact with Earth from 2169 to 2199. One of the mission objectives is to refine understanding of non-gravitational effects (such as the Yarkovsky effect) on this orbit, and the implications of those effects for Bennu's collision probability. Knowing Bennu's physical properties will be critical for future scientists to understand when developing an
asteroid impact avoidance Asteroid impact avoidance encompasses the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted, preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs w ...
mission.


Specifications

* Dimensions: Length , width , height * Width with
solar arrays A photovoltaic system, also called a PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to abs ...
deployed: * Power: Two solar arrays generate 1226 to 3000 Watts, depending on the spacecraft's distance from the Sun. Energy is stored in Li-ion batteries. * Propulsion system: Based on a
hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...
monopropellant system developed for the ''
Mars Reconnaissance Orbiter The ''Mars Reconnaissance Orbiter'' (''MRO'') is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA's Mars Exploration Program. It was launched from Cape Canaveral on Au ...
'', carrying of propellant and helium. * The sample-return capsule reentered the Earth's atmosphere with a parachute assisted landing. The capsule with encased samples was retrieved from Earth's surface and is being studied, as was done with the '' Stardust'' mission.


Instruments

In addition to its telecommunication equipment, the spacecraft carries a suite of instruments to image and analyze the asteroid on many wavelengths, and retrieve a physical sample to return to Earth.
The Planetary Society The Planetary Society is an American internationally-active non-governmental nonprofit organization. It is involved in research, public outreach, and political space advocacy for engineering projects related to astronomy, planetary science, a ...
coordinated a campaign to invite interested persons to have their names or artwork on the mission's spirit of exploration saved on a microchip carried in the spacecraft.


OCAMS

The OSIRIS-REx Camera Suite (OCAMS) consists of the PolyCam, the MapCam, and the SamCam. Together, they acquire information on asteroid Bennu by providing global mapping, sample site reconnaissance and characterization, high-resolution imaging, and records of the sample acquisition. * PolyCam, an telescope, acquired visible-light images with increasingly higher resolution on approach the asteroid and high-resolution surface images from orbit * MapCam searches for satellites and outgassing plumes. It maps the asteroid in four blue, green, red and near infrared channels, and informs the model of Bennu's shape and provides high resolution imaging of the potential sample sites * SamCam continuously documents the sample acquisitions


OVIRS

The OSIRIS-REx Visible and IR Spectrometer (OVIRS) is a
spectrometer A spectrometer () is a scientific instrument used to separate and measure Spectrum, spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomeno ...
which maps minerals and organic substances on the asteroid's surface. It provides full-disc asteroid spectral data at 20 m resolution. It maps blue to near-infrared, , with a
spectral resolution The spectral resolution of a spectrograph, or, more generally, of a frequency spectrum, is a measure of its ability to resolve features in the electromagnetic spectrum. It is usually denoted by \Delta\lambda, and is closely related to the resolvi ...
of . This data was used in concert with OTES spectra to guide sample-site selection. The spectral ranges and resolving powers are sufficient to provide surface maps of
carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...
s,
silicate A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used ...
s,
sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
s,
oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
s, adsorbed water and a wide range of
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
s.


OTES

The OSIRIS-REx Thermal Emission Spectrometer (OTES) provides thermal emission spectral maps and local spectral information of candidate sample sites in the
thermal infrared A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
channel covering 4–50 μm, again to map mineral and organic substances. The
wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...
range, spectral resolution, and radiometric performance are sufficient to resolve and identify silicates, carbonates, sulfates, phosphates, oxides, and hydroxide minerals. OTES is also used to measure the total thermal emission from Bennu in support of the requirement to measure emitted radiation globally. Based on the performance of Mini-TES in the dusty surface environment of Mars, OTES was designed to be resilient to extreme dust contamination on the optical elements.


REXIS

The Regolith X-ray Imaging Spectrometer (REXIS) provided an
X-ray spectroscopy X-ray spectroscopy is a general term for several Spectroscopy, spectroscopic techniques for characterization of materials by using x-ray radiation. Characteristic X-ray spectroscopy When an electron from the inner shell of an atom is excited b ...
map of Bennu to map element abundances. REXIS was a collaborative development by four groups within
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...
(MIT) and
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
, with the potential to involve more than 100 students throughout the process. REXIS was based on flight heritage hardware, thereby minimizing elements of technical risk, schedule risk, and cost risk. REXIS is a coded aperture soft X-ray (0.3–7.5 keV) telescope that images X-ray fluorescence line emission produced by the absorption of solar X-rays and the
solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
by elements in the regolith of Bennu leading to local X-ray emissions. Images were formed with 21 
arcminute A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
resolution (4.3 m spatial resolution at a distance of 700 m). Imaging was achieved by correlating the detected X-ray image with a 64×64 element random mask (1.536 mm pixels). REXIS stored data for each X-ray event to maximize data storage usage and minimize the risk. The
pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...
s were addressed in 64×64 bins and the 0.3–7.5 keV range was covered by five broad bands and 11 narrow line bands. A 24-second resolution time tag was interleaved with the event data to account for Bennu rotation. Images were reconstructed on the ground after downlink of the event list. Images were formed simultaneously in 16 energy bands centered on the dominant lines of abundant surface elements from O-K (0.5 keV) to Fe-Kß (7 keV) as well the representative continuum. During orbital phase 5B, a 21-day orbit 700 m from the surface of Bennu, a total of at least 133 events/asteroid pixel/energy band were expected under 2 keV; enough to obtain significant constraints on element abundances at scales larger than 10 m. On 11 November 2019, while observing the asteroid with REXIS, university students and researchers involved in the mission unexpectedly discovered an X-ray burst from a
black hole A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...
named MAXI J0637-430 located 30,000 light-years away.


OLA

The OSIRIS-REx Laser Altimeter (OLA) is a scanning and
lidar Lidar (, also LIDAR, an acronym of "light detection and ranging" or "laser imaging, detection, and ranging") is a method for determining ranging, ranges by targeting an object or a surface with a laser and measuring the time for the reflected li ...
instrument that will provide high resolution topographical information throughout the mission. The information received by OLA creates global
topographic Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the landforms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scienc ...
maps of Bennu, local maps of candidate sample sites, ranging in support of other instruments, and support navigation and gravity analyses. OLA scans the surface of Bennu at specific intervals to rapidly map the entire surface of the asteroid to achieve its primary objective of producing local and global topographic maps. The data collected by OLA will also be used to develop a control network relative to the center of mass of the asteroid and to enhance and refine gravitational studies of Bennu. OLA has a single common receiver and two complementary transmitter assemblies that enhance the resolution of the information brought back. OLA's high-energy laser transmitter is used for ranging and mapping from . The low-energy transmitter is used for ranging and imaging from . The repetition rate of these transmitters sets the data acquisition rate of OLA. Laser pulses from both the low and high energy transmitters are directed onto a movable scanning mirror, which is co-aligned with the field of view of the receiver telescope limiting the effects of background solar radiation. Each pulse provides target range, azimuth, elevation, received intensity and a time-tag. OLA was funded by the
Canadian Space Agency The Canadian Space Agency (CSA; ) is the national space agency of Canada, established in 1990 by the ''Canadian Space Agency Act''. The President of the Canadian Space Agency, president is Lisa Campbell (civil servant), Lisa Campbell, who took ...
(CSA) and was built by MDA at
Brampton Brampton is a city in the Canadian Provinces and territories of Canada, province of Ontario, and the regional seat of the Regional Municipality of Peel. It is part of the Greater Toronto Area (GTA) and is a List of municipalities in Ontario#L ...
,
Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
, Canada. OLA was delivered for integration with the spacecraft on 17 November 2015. The lead instrument scientist of OLA is Michael Daly from
York University York University (), also known as YorkU or simply YU), is a public university, public research university in Toronto, Ontario, Canada. It is Canada's third-largest university, and it has approximately 53,500 students, 7,000 faculty and staff, ...
.


TAGSAM

The sample-return system, called Touch-And-Go Sample Acquisition Mechanism (TAGSAM), consists of a sampler head with an articulated arm. An on-board nitrogen source supports up to three separate sampling attempts to acquire at least of sample in all. The surface contact pads also collect fine-grained material. Highlights of the TAGSAM instrument and technique include: * Relative approach velocity of * Contact within of selected location * OCAMS documents sampling at 1 Hz * Collect samples in less than five seconds, direct nitrogen (N2) annular jet fluidizes regolith, surface-contact pad captures surface sample * Verify bulk sample collection via spacecraft inertia change; surface sample by imaging sampler head * Sampler head stored in sample-return capsule and returned to Earth


Cooperation with JAXA

Hayabusa2 is a similar mission from
JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
to collect samples from near-Earth asteroid 162173 Ryugu. It arrived at the
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
in June 2018, left in November 2019 after two successful sample collections, and returned to Earth in December 2020. The recovery capsule of Hayabusa2 re-entered Earth atmosphere and landed in Australia, as planned, on 5 December 2020. The sample contents were to be extensively analyzed, including water content, to provide clues on the initial formation of the asteroid. The main module of Hayabusa2 is performing a swing-by procedure to "push" it onward to its next destination, asteroid 1998KY26, by 2031. Because the two missions were similar and had overlapping timelines (OSIRIS-REx was still in the return phase), NASA and JAXA signed an agreement to collaborate on sample exchange and research. The two teams visited each other, with representatives from JAXA visiting the OSIRIS-REx Science Operations Center at the
University of Arizona The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...
, and members of the OSIRIS-REx team traveling to Japan to meet with the Hayabusa2 team. The teams are sharing software, data, and techniques for analysis, and will eventually exchange portions of the samples that are returned to Earth.


OSIRIS-REx II

OSIRIS-REx II was a 2012 mission concept to replicate the original spacecraft for a double mission, with the second vehicle collecting samples from the two moons of Mars, Phobos and Deimos. It was stated that this mission would be both the quickest and least expensive way to get samples from the moons. Mars I and II are now the aims of another mission, led by JAXA, called MMX, to be launched in 2026.


Gallery

File:Tour of Asteroid Bennu.webm, Narrated tour of Bennu's most prominent surface features, as seen by OSIRIS-REx File:Asteroid Bennu's Surprising Surface Revealed by OSIRIS-REx (long form).webm, Effects of OSIRIS-REx sampling attempt on Bennu OSIRIS-REx_First_Image_of_Asteroid_Bennu.gif, First images of asteroid Bennu (August 2018). OSIRIX-REx views Asteroid Bennu.jpg, Asteroid Bennu from away (29 October 2018) NASA-EarthMoonLowerLeft-BennuAsteroidUpperRight-20190108.jpg, Earth-Moon (lower left) and asteroid Bennu (upper right) (December 2018) OSIRIS-REx SRC and Bennu.png, The Sample Return Capsule (SRC) with asteroid Bennu in the background (December 2019) OSIRIS-REx Sampling Before and After (Dated Frames).gif, The "Nightingale" sample site pictured before and after the sampling maneuver. File:Maps14227-fig-0004-m.jpg, The opened return capsule


See also

* *


Notes


References


External links

* mission website at
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
* mission website at the
University of Arizona The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...
*
Video (2:53)
– Asteroid Bennu Mission Overview (
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
; 11 May 2021). {{Portal bar, Spaceflight, Astronomy, Space Astrobiology space missions Missions to near-Earth asteroids NASA space probes New Frontiers program Orbiters (space probe) Planetary defense Sample return missions Spacecraft launched by Atlas rockets Space probes launched in 2016 Spacecraft which reentered in 2023 Articles containing video clips