Planetary Defense
 
June 30, 2016:  Dinosaurs were fearsome creatures. Some had thick scales,
sharp teeth, and, in many cases, lightning-fast reflexes.
 
One thing they didn't have: a planetary defense office.
 
When an asteroid targeted Earth 65 million years ago, it took those masters of
Earth by complete surprise. While we know of no large object that is on a
collision course with Earth in the next 100 years, descendants of survivors
from that catastrophic impact are determined not to make the same mistake.
 
https://www.youtube.com/watch?v=B1UQHhZHeiA
 
In 2016, human astronomers now routinely scan the heavens for signs of
potentially hazardous objects. When one is discovered, alerts are issued to
observers around the world so space rocks cannot easily disappear into the
blackness of space. NASA-funded survey projects have found 98 percent of the
known catalogue of almost 15,000 near-Earth objects-asteroids and comets whose
orbits periodically bring them within 30 million miles of Earth's orbit. The
list is growing at a rate of about 1,500 per year.
 
Meanwhile, researchers are giving serious thought to an even bigger problem:
What would we do if a dangerous asteroid is discovered? How will we know if
and when it will impact? Is it possible to deflect or destroy it before it
reaches Earth?
 
All of this work-from discovery to tracking to potential mitigation-is being
done by a sprawling network of government agencies, private and public
universities, and both amateur and professional astronomers. Helping them work
together is the job of NASA's Planetary Defense Coordination Office.
 
Lindley Johnson, Planetary Defense Officer at NASA Headquarters in Washington,
DC says, "Planetary Defense is a team sport. This office was established at
NASA Headquarters to coordinate the players in planetary defense related
activities across NASA, other US government agencies, and with international
efforts and projects to detect any asteroid impact hazard and plan the
appropriate response."
 
A recent real world example illustrates how this all works.
 
Paul Chodas, manager for NASA's Center for Near Earth Object Studies at the
Jet Propulsion Laboratory, describes what happened: "The object was first
detected by the NASA-funded Catalina Sky Survey near Tucson, Arizona on
October 3rd, 2015 and tagged as detection WT1190F."
 
Within a couple of days, astronomers suspected it was probably an artificial
object: It was faint and small with its motion visibly altered by the gentle
pressure of sunlight-a bit like a solar sail or perhaps a hollow rocket body.
 
As tracking data accumulated from multiple observers, astronomers realized
that they would get a closer look. This would be a real world case to exercise
the team's skills. WT1190F was predicted to hit Earth on Friday, Nov. 13,
2015. Orbit calculations by JPL analysts pinpointed the impact time and site:
WT1190F would burn into the atmosphere off the coast of Sri Lanka.
 
For years, Peter Jenniskens of the SETI institute working with NASA's Ames
Research Center has been leading teams researching entry dynamics on airborne
campaigns to observe objects ripping through Earth's atmosphere. In 2006, for
instance, they recorded the return of NASA's Stardust Sample Return Capsule
with its cargo of cometary dust. They've also observed a number of defunct
spacecraft re-entries and a few natural meteor events.
 
Supported in part by the United Arab Emirates Space Agency and the
International Astronomy Center, Jenniskens assembled a group of experts to
witness the re-entry of WT1190F. They flew to the Indian Ocean on a G450
aircraft armed with cameras and spectrometers. Exactly at the time and place
predicted by NASA's Near Earth Object Observations program, WT1190F produced a
magnificent fireball in broad daylight.
 
Jenniskens says, "The spectra of one large fragment contained bands of
titanium oxide and a line of hydrogen. So the object could have been a
titanium-walled vessel containing residual fuel."
 
Chodas, who had been attempting to reconstruct WT1190F's past orbital motion
says, "My educated guess, is that it was Lunar Prospector's trans-lunar
injection module, which had a titanium case. Although we may never know for
sure."
 
One thing is certain: Astronomers supported by NASA found it, tracked it, and
predicted where it would hit with pinpoint accuracy. These are exacting skills
that will come in handy the next time an actual asteroid comes to visit.
 
For more about asteroids and NASA's planetary defense capabilities, go to
www.nasa.gov/planetarydefense.
 
For more on objects both near and far from Earth, stay tuned to 
cience.nasa.gov.
 
 
Regards,
 
Roger

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