The next generation of satellites is made up of modest cubes about the size of a coffee mug, now being developed to circle Earth, where they monitor space weather, observe the atmosphere, and even test the feasibility of using a sun-powered sail to tow space junk. Over the past seven years, these diminutive cube satellites, or CubeSats, have grown in importance, now poised to have a potentially profound impact on the big-budget space industry, similar to the way that personal computers transformed access and innovation in computing.