To Bennu and Back   
       
   Sept. 8, 2016:  NASA is launching a spacecraft to visit an asteroid. and   
   return to tell the tale.   
       
   OSIRIS-REx is scheduled to blast off from Cape Canaveral on September 8, 2016,   
   on a mission to orbit, map and collect samples from the asteroid Bennu, and   
   return to Earth 7 years later.   
       
   https://www.youtube.com/watch?v=IO1jvN6AxEo   
       
   Discovered in 1999 by the NASA-funded LINEAR asteroid survey, Bennu measures   
   about 1650 feet across and weighs over 60 million tons. Imagine a boulder the   
   height of the Empire State Building-that's about the size of Bennu.   
       
   So, why Bennu? Because the asteroid is interesting due to its size and   
   composition, and it is accessible to be sampled.   
       
   Bennu is a primitive and carbon-rich asteroid. Primitive asteroids contain   
   material that has not changed significantly since they formed over 4.5 billion   
   years ago. The analysis of any organic material found on Bennu will give   
   scientists an inventory of the materials present at the beginning of the solar   
   system that may have had a role in the origin of life on earth, and   
   potentially elsewhere.   
       
   Indeed, Dante Lauretta of the University of Arizona, Principal Investigator on   
   the OSIRIS-REx mission says mapping and sampling the space rock "can   
   potentially hold answers to the most fundamental questions human beings ask,   
   like 'Where do we come from?'"   
       
   To get to Bennu, OSIRIS-REx will perform a series of deep space maneuvers,   
   first orbiting the sun for a year and then using Earth's gravity to be slung   
   towards Bennu.   
       
   The spacecraft will spend a year flying in close proximity to Bennu - its five   
   instruments imaging the asteroid, documenting its lumpy shape, and surveying   
   its chemical and physical properties.   
       
   In July 2020, OSIRIS-REx will approach Bennu and execute its touch-and-go - or   
   TAG - maneuver. A mechanical arm that functions like a combination sample   
   scoop and pogo stick will be extended from the spacecraft. The spacecraft will   
   slowly approach the asteroid until the sample head at the end of the arm gives   
   a gentle "high five" to the surface. The maneuver may be executed up to three   
   times, and OSIRIS-REx could leave Bennu with up to 4.4 pounds of sample   
   material from the asteroid.   
       
   Researchers will be keen to learn about Bennu for another reason, too. Bennu   
   orbits the sun between Venus and Mars so it crosses Earth's orbit frequently   
   and comes close to Earth every six years. In 2135, Bennu will make an   
   especially close approach to Earth, just within the Moon's orbit.  This will   
   change Bennu's orbit, and it is more difficult to predict how much closer it   
   may come to the Earth after that close encounter. Lauretta says, "We need to   
   learn as much as about Bennu as we can."   
       
   Predicting a small asteroid like Bennu's exact course is somewhat tricky, due   
   to the Yarkovsky effect. The dark asteroid absorbs sunlight and then gives it   
   off as heat, which serves as a gentle thruster that gradually shifts its path.   
       
   Edward Beshore of the University of Arizona, Deputy Principal Investigator for   
   OSIRIS-REx says, "We'll get accurate measurements of the Yarkovsky effect on   
   Bennu by precisely tracking OSIRIS-REx as it orbits the asteroid."   
       
   If all goes as planned, OSIRIS-REx will fire its main engines in March 2021   
   and begin its journey back to Earth. The samples will arrive in September   
   2023, when a capsule containing bits of Bennu will land at the Utah Test and   
   Training Range. From there, the capsule and its precious contents will travel   
   to NASA's Johnson Space Center in Houston, TX, where hands-on analysis of this   
   ancient asteroid will begin by mission scientists and then by scientists from   
   all over the world.   
       
   For updates on the mission to Bennu and back, go to www.asteroidmission.org   
       
   For more on objects in and around our solar system, stay tuned to   
   science.nasa.gov   
       
       
   Regards,   
       
   Roger   
      
   --- DB 3.99 + W10 (1607)   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)