|Mission type||Asteroid sample return|
|Mission duration||7 years
505 days at asteroid
|Launch mass||1,529 kg (3,371 lb)|
|Dimensions||2 m (6.6 ft) cube|
|Start of mission|
|Launch date||September 2016 (planned)|
|Rocket||Atlas V 411|
|Launch site||Cape Canaveral SLC-41|
|Contractor||United Launch Alliance|
|End of mission|
|Landing site||Utah Test and Training Range|
|(101955) Bennu orbiter|
|(101955) Bennu lander|
|Sample mass||up to 2 kg (4.4 lb)|
OSIRIS-REx is a planned asteroid study and sample return mission. It is a planetary science mission, the third selected in the New Frontiers Program, after Juno and New Horizons. The mission is planned for a 2016 launch and will study and return a sample of asteroid 101955 Bennu (formerly designated 1999 RQ36), a carbonaceous asteroid, to Earth for detailed analyses in 2023. Material returned is expected to enable scientists to learn more about the time before the formation and evolution of the Solar System, initial stages of planet formation, and the source of organic compounds which led to the formation of life.
OSIRIS-REx stands for Origins Spectral Interpretation Resource Identification Security Regolith Explorer
The mission, developed by the University of Arizona's Lunar and Planetary Laboratory, NASA Goddard Space Flight Center and Lockheed Martin Space Systems, is planned for launch in September 2016. After traveling for approximately two years, the spacecraft will rendezvous with asteroid 101955 Bennu (1999 RQ36), and begin 505 days of surface mapping at a distance of approximately 5 km (3.1 mi). Results of that study will be used by the mission team to select the sample site and the gradual process of approaching, but not landing, and ultimately extending a robotic arm to gather the sample.
An asteroid was chosen as the target of study because asteroids are a 'time capsule' from the birth of our Solar System. In particular, 101955 Bennu was selected because of the availability of pristine carbonaceous material, a key element in organic molecules necessary for life as well as representative of matter from before the formation of Earth. Organic molecules have previously been found in meteorite and comet samples, indicating that some ingredients necessary for life can be created in space.
Following collection (from 60 grams to 2 kilograms, or 2.1 oz to 4.4 lb), the sample will be returned to Earth in a capsule similar to that which returned the samples of comet 81P/Wild on the Stardust spacecraft. The return trip to Earth will be shorter, allowing the sample to return and land at the Utah Test and Training Range in 2023. The capsule will then be transported to the Johnson Space Center for processing in a dedicated research facility.
Launch is planned for September of 2016. On August 5, 2013, NASA announced OSIRIS-REx would launch on an Atlas V 411. Interested persons are welcome to have their names inscribed on a microchip to be carried in the spacecraft. 
Telescopic observations have helped define the orbit of 101955 Bennu, a near-Earth object with a mean diameter in the range of 480 to 511 meters (1575 to 1678 ft). It completes an orbit of the Sun 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 in the period 2169 to 2199. Part of the OSIRIS-REx mission 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.
Telescopic observations have revealed some basic properties of 101955 Bennu. They indicate that 101955 Bennu is very dark and is classified as a B-type asteroid, a sub-type of the carbonaceous C-group asteroids. Such asteroids are considered "primitive", having undergone little geological change from their time of formation.
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 material.
- 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, and spectral properties of the regolith 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.
- Size: 2 m (6.6 ft) cube.
- Solar arrays: 8.5 square metres (91 sq ft).
- Power: Solar arrays and Li-ion batteries.
- The Sample Return Capsule (SRC) will be used for entering the Earth's atmosphere. The capsule with encased samples will be retrieved from Earth's surface and studied, as was done with the Stardust mission.
In addition to its telecommunication equipment, the spacecraft will carry a suite of instruments which will study the asteroid in many wavelengths, as well as image the asteroid, and retrieve a physical sample to return to Earth.
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 8-inch telescope, acquires images with increasingly higher resolution as the spacecraft approaches the asteroid.
- MapCam searches for satellites and outgassing plumes. It maps the asteroid in 4 different colors, informs our model of asteroid shape and provides high resolution imaging of the sample-site.
- SamCam continuously documents the sample acquisitions.
The OSIRIS-REx Laser Altimeter (OLA) is a scanning and LIDAR instrument that will provide high resolution topographical information throughout the entire mission. The information received by OLA will create global topographic maps of Bennu, local maps of candidate sample sites, ranging in support of other instruments, and support navigation and gravity analyses.
OLA will scan the surface of Bennu at specific intervals in the mission to rapidly map out the entire surface of the asteroid to achieve its primary objective of producing local and global topographic maps. What OLA brings back about Bennu will also be used to develop a control network relative to the center of mass of the asteroid and enhance and refine gravitational studies of Bennu.
OLA has a single common receiver and two complementary transmitter assemblies which enhance the resolution of the information brought back. OLA’s high-energy laser transmitter is used for ranging and mapping from 1 to 7.5 km. The low-energy transmitter is used for ranging and imaging at smaller distances (500 m to 1 km). 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.
The OSIRIS-REx Visible and IR Spectrometer (OVIRS) is a spectrometer, which measures light to provide mineral and organic spectral maps and local spectral information of candidate sample sites. It also provides full-disc asteroid spectral data, global spectral maps (20 m resolution), and spectra of the sample site (0.08–2 m resolution). These data will be used in concert with OTES spectra to guide sample-site selection. These spectral ranges and resolving powers are sufficient to provide surface maps of mineralogical and molecular components including carbonates, silicates, sulfates, oxides, adsorbed water and a wide range of organic compounds.
It provides at least two spectral samples per resolution element taking full advantage of the spectral resolution. OVIRS spectra will be used to identify volatile and organic-rich regions.
The OSIRIS-REx Thermal Emission Spectrometer (OTES) provides mineral and thermal emission spectral maps and local spectral information of candidate sample sites by collecting thermal infrared data from 4 - 50 µm.
OTES provides full-disc Bennu spectral data, global spectral maps, and local sample site spectral information used to characterize the global, region, and local mineralogic composition and thermal emission from the asteroid surface. The wavelength range, spectral resolution, and radiometric performance are sufficient to resolve and identify the key vibrational absorption features of silicate, carbonate, sulfate, phosphate, oxide, and hydroxide minerals. OTES is also used to measure the total thermal emission from Bennu, which drives the requirement to measure emitted radiation globally. Based on the performance of Mini-TES in the dusty surface environment of Mars, OTES is resilient to extreme dust contamination on the optical elements.
The Regolith X-ray Imaging Spectrometer (REXIS) will provide an X-ray map of Bennu, complementing core OSIRIS-REx mission science. REXIS brings the strengths of four groups within Massachusetts Institute of Technology (MIT) and Harvard University utilizing the flight-proven Conceive, Design, Implement and Operate (CDIO) curriculum, with the potential to involve more than 100 students throughout the process. REXIS is 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 interaction of solar X-rays and the solar wind with the regolith of Bennu. Images are formed with 21 arcminute resolution (4.3 m spatial resolution at a distance of 700 m). Imaging is achieved by correlating the detected X-ray image with a 64 x 64 element random mask (1.536 mm pixels). REXIS will store each X-ray event data in order to maximize the data storage usage and to minimize the risk. The pixels will be addressed in 64 x 64 bins and the 0.3–7.5 keV range will be covered by 5 broad bands and 11 narrow line bands. A 24 s resolution time tag will be interleaved with the event data to account for Bennu rotation. Images will be reconstructed on the ground after downlink of the event list. Images are 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 are expected under 2 keV; enough to obtain significant constraints on element abundances at scales larger than 10 m.
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 will support up to three separate sampling attempts for a minimum total amount of 60 g of sample. The surface contact pads will also collect fine-grained material.
Highlights of the TAGSAM instrument and technique include:
- Slowly approach surface at 0.2 m/s,
- Contact within 25 m of selected location,
- OCAMS documents sampling at 1 Hz,
- Collect samples in ~5 s, 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 (SRC) and returned to Earth.
OSIRIS-REx 2, if funded, would make it a double mission collecting samples from the two Mars moons for return to the Earth. Proposed in n 2012, it was stated that this mission would be the both quickest and least expensive way to get samples from the Moons.
Illustration of OSIRIS-REx collecting a sample from asteroid Bennu.
Sample return capsule from the Stardust mission.
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