Incoherent Scatter Measurements of E- and F-Region Density, Temperatures, and Collision Frequency at Millstone Hill

The Millstone Hill incoherent (Thomson) scatter radar system has been operated since 1963 to perform a synoptic study of F2-region electron densities, and electron and ion temperatures. These measurements have been conducted by transmitting single long pulses and performing digital sweep integration and spectrum analysis of the reflected signals. This report describes changes made to the system in 1969 to permit extensions of the measurements to altitudes below 200 km (i.e., the E- and F1-regions). These changes include modifications to the radar timing equipment to permit the transmission of close-spaced pairs of pulses from which the echo autocorrelation function can be determined in the computer by processing appropriately spaced pairs of echo samples. By operating the radar coherently, it has also been possible to subtract the unwanted (stronger) clutter signals from the ionospheric echoes. Samples are presented of the results that can now be obtained from these programs