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article imageAfter two years, NASA's OSIRIS-REx closes in on asteroid Bennu

By Karen Graham     Aug 21, 2018 in Science
NASA's OSIRIS-REx spacecraft has met another milestone in its seven-year mission. OSIRIS began its final approach toward the 1,650-foot-wide space rock on August 17, officially beginning its "asteroid operations" phase.
Well, for those of us following the OSIRIS-REx mission, keep in mind that the spacecraft still has about 1.2 million miles (2 million kilometers) to go before it meets Bennu face-to-face. OSIRIS-REx won't arrive in orbit around Bennu until December 3, 2018.
The $800 million OSIRIS-REx mission (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) began with the launch of the spacecraft on September 8, 2016, from Cape Canaveral Air Force Station in Florida.
Image of asteroid 101955 Bennu taken by Indian Space Research Organization on June 29  2014.
Image of asteroid 101955 Bennu taken by Indian Space Research Organization on June 29, 2014.
And if everything goes according to plan, after OSIRIS-REx reaches orbit abound Bennu in December, it will begin a two-year study of the asteroid, gathering a variety of data. It is interesting that Bennu will be the smallest object that NASA has ever tried to orbit.
At 493 meters (1,617 feet) wide, and about the size of the Empire State Building, Bennu won't be that easy to orbit around for two years. In keeping the spacecraft on orbit, scientists have to contend with is the low gravity, solar winds, and pressures from solar and re-emitted infrared radiation. All of these things could affect the orbit.
Scanning the surface of Bennu will take six months, and a special instrument was contributed by the Canadian Space Agency (CSA) that will create 3-D maps of the asteroid's surface to aid in selecting the perfect site to take a sample.
Called OLA (OSIRIS-REx Laser Altimeter) the instrument is an advanced LIDAR (Light Detecting and Ranging) system that will scan the entire surface of the asteroid. Along with other instruments, OLA will be creating detailed 3-D maps of every crack, canyon, and open space, providing details about the topography and interior geology of the space rock.
Only after the complete scanning and other data retrieval will OSIRIS-REx swoop down and snag a sizable sample of asteroid material before leaving Bennu in March 2021. This cosmic mix of dirt and gravel will come down to Earth in a special return capsule in September 2023.
More about OSIRISREx, Asteroid, Bennu, sampling mission
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