The relativistic electron flux in the outer radiation belt can vary by orders of magnitude during geomagnetic storms, fast solar wind streams and other space weather events. These variations are driven by acceleration, transport and loss processes associated with many different types of waves in the ULF to VLF frequency range. Periods of high flux can cause satellite charging leading to disruptions to satellite services and in rare cases satellite loss. Here we examine the time history of the electron flux at geostationary orbit using data from the GOES satellite. We consider the peak flux and 24 hour fluence and examine periods where satellites may be a risk. We develop a model for satellite charging that takes into account the properties of difference dielectric materials. We demonstrate that the charging risk is far more complicated than simply looking at the electron flux and depends critically on the time history of the electron flux. We discuss what this means in terms of protecting satellites and the difficulty of calculating the risk for orbits where there are little data, such as medium Earth orbit.