The National Science Foundation supports four large incoherent-scatter radar facilities and the SuperDARN coherent scatter radar system. The incoherent-scatter radars are located along a longitudinal chain from Greenland to Peru. Each of the incoherent-scatter facilities is also equipped with powerful optical diagnostic instruments. The SuperDARN consists of a number of coherent-scatter HF radars in both the northern and southern hemispheres. The major goal of Geospace Facilities (GF) is to promote basic research on the structure...