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From: Roger Nelson
To: All
Date: 2017-08-01 20:42:16
Subject: The Hunt for Asteroids

The Hunt for Asteroids
 
A few NASA-funded astronomer teams are always on the hunt for potentially
hazardous near-Earth objects, asteroids and comets whose orbits
periodically bring them within 30 million miles of Earth's orbit. At NASA,
the Planetary Defense Coordination Office supports the search programs,
while also planning and coordinating any response to possible asteroid
impacts.
 
https://www.youtube.com/watch?v=MQi0R6PCROI
 
Lindley Johnson Heads up this NASA office. He says, "We oversee
several NASA-supported search programs that detect and track near-Earth
objects," he explains. "The rate of asteroid discovery has
increased considerably due to these dedicated astronomers and to upgraded
telescopes coming online in recent years."
 
As part of NASA's planetary defense strategy, the Center for Near Earth
Object Studies at the Jet Propulsion Laboratory analyzes the data collected
on near-Earth objects and publishes the running statistics on numbers and
types discovered.
 
Johnson says, "After almost 20 years of searching, over 93% of the
near-Earth objects larger than one kilometer (.62 miles) are already
discovered. The focus is now on finding 90% of those larger than 140 meters
(450 feet). Almost 7,700 of these are now being tracked, but we believe
there are still over twice that number out there to be found."
 
NASA is not only hunting asteroids, it's also working on ways to defend
Earth against them. Astrodynamicists at the Center for Near Earth Object
Studies predict orbits a century into the future to determine whether there
are any risks for impact.
 
Johnson says, "Asteroid impacts are predictable and preventable. If we
can find them before they strike, we can precisely predict their paths and
time of possible impact. And we now have the space technologies to divert
them."
 
For example, if an approaching asteroid were detected early enough, its
path could be altered by using a large spacecraft as a `gravity tractor.'
It would fly alongside the asteroid for an extended time and slowly pull it
out of Earth's path using nature's virtual tug-rope -- gravity. Another
method involves sending a heavy, high-speed spacecraft into the path of an
approaching object to strike it at the right time and place. This
technique, called the kinetic impactor, could slow or speed up the asteroid
into a different trajectory, away from the Earth's path.
 
And then there's the Hollywood option.
 
"This is a last resort measure," says Johnson.  "It involves
exploding a device close enough to an asteroid that the super-heated
surface material blows off, creating a powerful, rocket-like push. Though
quite effective if time is short, it would take a lot of coordination and
approval not only within the U.S. government, but also with the
international community. Another reason we should find any impactors as
early as possible is so more benign methods can be used."
 
All these techniques are in some stage of study or design. Meanwhile, the
hunt for potentially hazardous asteroids goes on.
 
Johnson says, "After all, at NASA every day is an Asteroid Day."
 
For more on objects in and around Earth's neighborhood, visit science.nasa.gov
 
 
Regards,
 
Roger

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