Designing systems and technologies that can withstand effects of the space environment requires good knowledge of "space climate" and, in many cases, of extreme space weather events. Designers need, and refer to, past space weather conditions in order to produce systems that can survive the harsh conditions of geospace. Thus data centers such as the NOAA National Geophysical Data Center (NGDC) and the NASA National Space Science Date Center (NSSDC) are essential for understanding space climate and its changes with time.