The Radiation Assessment Detector, one of 10 instruments on board the next rover mission to Mars, is now collecting data during the long journey to the Red Planet. RAD, the only instrument scheduled to collect science data en route, will measure fluxes of solar energetic particles and galactic cosmic rays from inside the spacecraft in preparation for future human missions to Mars. Southwest Research Institute leads the RAD investigation on the Mars Science Laboratory, which launched Nov. 26. The MSL rover will arrive at Mars in August 2012 to assess the planet's past and present habitability.