The above image is a chart of charged particle flux observations of the Radiation Assessment Detector (RAD) aboard NASA's Mars Science Laboratory (MSL) during approximately 7 months of cruising between Earth and Mars. The inset at the upper-right compares the RAD particle flux observations with those of the Advanced Composition Explorer (ACE) spacecraft for March 5th through 15th. Image Credit: NASA
This is pretty cool. NASA's Mars Science Laboratory (MSL) has not even reached Mars, yet. But MSL is already doing work that benefit's future human spaceflight to Mars.
For nine months, ending in July, the MSL/Curiosity rover acted as a stunt double for astronauts, exposing itself to the same cosmic radiation humans would experience following the same route to Mars. During that time Curiosity was hit by five major solar flares and solar particle events. But rest assured that Curiosity is fine, though the data it transmitted back is invaluable.
Unlike previous Mars rovers, Curiosity is equipped with an instrument that measures space radiation, called the Radiation Assessment Detector (RAD). It 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 was key to the experiment. Being inside the MSL aeroshell and heat shield is similar to the way an astronaut would travel in a spacecraft. So Curiosity would absorb deep-space radiation storms the same way real astronauts would. Computer simulations on the effects of radiation exposure can be very complicated. But Curiosity's cruise time gave scientists a chance to measure what happens in a real-life situation.
Only the strongest radiation storms made it inside the spacecraft. Moreover, charged particles penetrating the hull were slowed down and fragmented by their interaction with the spacecraft's metal skin. And in addition, the spacecraft's hydrazine tanks and other components contributed 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. The MSL mission team plan to publish results in a peer-reviewed journal later this year.
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.
And now, the mission particulars...
The Mars Science Laboratory / Curiosity rover mission is managed for NASA’s Science Mission Directorate, Washington, D.C., by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena (Caltech). More information about Curiosity is online at www.nasa.gov/msl and mars.jpl.nasa.gov/msl . You can follow the mission on Facebook at: www.facebook.com/marscuriosity and on Twitter at: www.twitter.com/marscuriosity .