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

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 * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)