The device irradiates samples with alpha particles and maps the spectra of X-rays that are re-emitted for determining the elemental composition of samples.  Curiosity 's APXS was developed by the Canadian Space Agency .  MacDonald Dettwiler (MDA) , the Canadian aerospace company that built the Canadarm and RADARSAT , were responsible for the engineering design and building of the APXS. The APXS science team includes members from the University of Guelph , the University of New Brunswick , the University of Western Ontario , NASA , the University of California, San Diego and Cornell University .  The APXS instrument takes advantage of particle-induced X-ray emission (PIXE) and X-ray fluorescence , previously exploited by the Mars Pathfinder and the Mars Exploration Rovers .