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   
      
   --- DB 3.99 + Windows 10   
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