Hello All!   
      
   Curiosity's First Daredevil Stunt    
      
   August 2, 2012:  When Curiosity enters the Martian atmosphere on August 6th,   
   setting in motion "the seven minutes of terror" that people around the world   
   have anticipated since launch a year ago, the intrepid rover will actually be   
   performing the mission's second daredevil stunt.   
      
   The first was completed in July.   
      
   For the past nine months, Curiosity has been acting as a stunt double for   
   astronauts, exposing itself to the same cosmic radiation humans would   
   experience following the same route to Mars1.   
      
   "Curiosity has been hit by five major flares and solar particle events in the   
   Earth-Mars expanse," says Don Hassler of the Southwest Research Institute in   
   Boulder, Colorado. "The rover is safe, and it has been beaming back invaluable   
   data."    
      
   http://science.nasa.gov/media/medialibrary/2012/08/02/stuntdouble.jpg   
      
   Curiosity traveled to Mars in the belly of a space capsule akin to   
   human-crewed capsules.    
      
   Unlike previous Mars rovers, Curiosity is equipped with an instrument that   
   measures space radiation. The Radiation Assessment Detector, nicknamed "RAD,"   
   counts cosmic rays, neutrons, protons and other particles over a wide range of   
   biologically-interesting energies. RADs prime mission is to investigate the   
   radiation environment on the surface of Mars, but NASA turned it on during the   
   cruise phase so that it could sense radiation en route to Mars as well.   
      
   Curiosity's location inside the spacecraft is key to the experiment.   
      
   "Curiosity is riding to Mars in the belly of the spacecraft, similar to where   
   an astronaut would be," explains Hassler, RAD's principal investigator.  "This   
   means the rover absorbs deep-space radiation storms the same way a real   
   astronaut would."   
      
   Even supercomputers have trouble calculating exactly what happens when   
   high-energy cosmic rays and solar energetic particles hit the walls of a   
   spacecraft.  One particle hits another; fragments fly; the fragments   
   themselves crash into other molecules.   
      
   "It's very complicated.  Curiosity has given us a chance to measure what   
   happens in a real-life situation"    
      
   http://science.nasa.gov/media/medialibrary/2012/08/02/flux.jpg   
      
   http://science.nasa.gov/media/medialibrary/2012/08/02/attenuation.jpg   
      
   RAD charged particle flux observations during ~7 months of cruise included   
   contributions from 5 solar energetic particle events. The inset compares the   
   particle flux observed by RAD to that observed by instruments on the ACE   
   spacecraft. The MSL spacecraft structure (backshell, heatshield, etc.)   
   provided significant shielding from deep space radiation, significantly   
   reducing the particle flux compared to ACE.    
      
   Hassler says the walls of the Mars Science Lab spacecraft have performed as   
   expected: Only the strongest radiation storms have made it inside. Moreover,   
   charged particles penetrating the hull have been slowed down and fragmented by   
   their interaction with the spacecraft's metal skin.   
      
   "It's not only the walls that matter, however," he points out.  "The   
   spacecraft's hydrazine tanks and other components contribute some protection,   
   too."    
      
   Data from Curiosity will help sort out how different subsystems block and   
   respond to cosmic rays and solar radiation.  This is information designers of   
   human-crewed spacecraft urgently need to know.  "We plan to publish results in   
   a refereed journal later this year," says Hassler.   
      
   RAD was turned off July 13th in preparation for landing.  Mission controllers   
   will turn it on again after Curiosity sets down in Gale crater.  Then   
   researchers will learn what radiation awaits astronauts on the surface of Mars   
   itself.   
      
   "No one has ever before measured this kind of radiation from the surface of   
   another planet." Says Hassler, "we're just getting started."    
      
      
   Author: Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
      
   More Information    
   Footnote: (1) NASA engineered Curiosity to withstand the anticipated radiation   
   exposure.    
      
   Strange but True: Curiosity's Sky Crane -- Science@NASA    
      
   Opportunity Runs the First Martian Marathon -- Science@NASA    
      
   Mars Landing Sky Show -- Science@NASA   
       
      
      
   Regards,   
      
   Roger    
   --- timEd/386 1.10.y2k+   
    * Origin: NCS BBS - Houma, LA - (1:3828/7)