Incoherent Scattering of Radio Waves by Free Electrons with Applications to Space Exploration by Radar

Free electrons in an ionized medium scatter radio waves weakly. Under certain conditions only incoherent scattering exists. A powerful radar can detect the incoherent backscatter from the free electrons in and above the earth's ionosphere. The received signal is spread in frequency by the Doppler shifts associated with the thermal motion of the electrons. On the basis of incoherent backscatter by free electrons a powerful radar, but one whose components are presently within the state of the art, is capable of: 1) measuring electron density and electron temperature as a function of height and time at all levels in the earth's ionosphere and to heights of one or more earth's radii; 2) measuring auroral ionization; 3) detecting transient streams of charged particles coming from outer space; and 4) exploring the existence of a ring current. The instrument is capable of 1) obtaining radar echoes from the sun, Venus, and Mars and possibly from Jupiter and Mercury; and 2) receiving from certain parts of remote space hitherto-undetected sources of radiation at meter wavelengths.