EISCAT VHF Incoherent scatter radar

An incoherent scatter radar transmits a VHF or UHF radiowave of high power and a tiny fraction of the power is scattered back. The spectrum of the scattered signal depends on plasma waves propagating in the ionosphere and from the shape of the spectrum the temperature of electrons and ions can be determined. The scattered power or electron plasma frequency shift can give the electron density and the Doppler shift gives the ion drift velocity. The EISCAT Tromsø VHF radar was taken into use in 1985. It operates at 224 MHz and uses a 4-segment parabolic cylinder antenna of 40x120 m, which can point to zenith or low elevatin northward. The transmitter and receiver are split in two halves each connected to two of the segments. Only one half can transmit due to a klystron failure. The system nevertheless operates at a peak power above 1 MW.