STEREO-B is one of two spacecraft that make up NASA’s Solar Terrestrial Relations Observatory (STEREO). The goal of the program is to study the Sun and better understand its behavior. Specifically, STEREO aims to figure out the origins of coronal mass ejections — massive explosions of charged particles that sometimes shoot out from the Sun. These plasma bursts travel all the way to Earth and collide with our planet’s magnetic field, creating powerful geomagnetic storms that can damage communications satellites and mess with our planet’s power grid.