THE SONDRESTROM RADAR AND ACCOMPANYING GROUND-BASED INSTRUMENTATION

The Sondrestrom radar facility, funded by the NSF Upper Atmospheric Fa cilities Program, is operated and managed by SRI International. The fa cility is located on the west coast of Greenland, just north of the Ar ctic Circle, near 75 deg invariant magnetic latitude. The principal in strument at the facility is the incoherent scatter radar. The incohere nt scatter technique allows the direct measurement of ionospheric elec tron number density, ion velocity, and electron and ion temperature al ong the radar beam. Because the radar antenna is fully steerable these parameters can be determined as functions of horizontal distance and altitude. Additional ionospheric quantities can be derived using these measured parameters. As part of the ISTP mission, the radar will meas ure the spatial (horizontal and altitudinal) and temporal variations o f ionospheric parameters including electron density, large scale elect ric field. conductivity, currents, and energy input. Repetitive measur ements define variations of parameters with local time, as well.