RainCube is short for Radar in a CubeSat. A CubeSat is a small, cube-shaped satellite that is only about 4 inches (10 centimeters) on each side. When it launched, RainCube was six CubeSats joined together. It is the first CubeSat with an active radar–a detector that uses radio waves. RainCube studies Earth’s precipitation and can improve weather forecasting.