Abstract: Understanding magnetosphere/ionosphere coupling requires understanding the dynamics of the transition region between the two, Earth’s plasmasphere. The dynamic of the plasmasphere, a region of cold and dense plasma, is poorly characterized due to the paucity of in situ data available, making it difficult to construct a global plasmasphere picture. The advent of the Global Positioning System (GPS) measurements from satellite-based receivers has dramatically increased the number of available measurements from the plasmasphere and the top ionosphere.  In this talk, I will present plasmasphere data assimilation and imaging techniques utilizing upward looking GPS measurements from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites. I will also talk about a CubeSat mission concept aimed at imaging of the top ionosphere and plasmasphere.