Measurements of Quasi-Static and Low-Frequency Electric Fields with Spherical Double Probes on the ISEE-1 Spacecraft

The spherical double-probe electric-field experiment on the ISEE-1 spacecraft is described. It is shown that the instrument measures magnetospheric, magnetosheath, and solar wind electric fields with a sensitivity well below one mV/m. Design features and diagnostic experiments performed in orbit to understand the instrument operation are discussed.