TABLE OF CONTENTS In the late 1950s and early 1960s, the rapid increases in the power-aperture product of radars created a need to understand the propagating medium better, particularly the ionosphere. As a result, ionospheric radars began to appear. Several located in the arctic regions had the specific objective of understanding the auroral ionosphere, but two located near the equator (one in Peru and the other in Puerto Rico) had more generalized missions of ionospheric physics and radio astronomy. We shall discuss the one in Puerto Rico, known as the Arecibo Ionospheric Obser vatory [Air Force Office of Scientific Research, 1963].
The Arecibo radar has the planets of our solar system out to Jupiter within range and can gather information about surface properties (RCS), rotational rates (Doppler), and orbits (range and range rate tracking). In fact, it has made a synthetic aperture radar map of the planet Venus [Rogers and Ingalls, 1970]. However, the radar s primary purpose is to study the Earth s ionosphere. The method is to illuminate the ionosphere (from 50 km to several thousand kilometers altitude) and examine the backscatter. By application of Maxwell s equations to the data in the radar returns, the electron density, the electron temperature, and the strength of the Earth s magnetic field can be inferred.
Arecibo s antenna is a 305-m aperture spherical reflector located in a natural bowl. Because it is not a paraboloid, it needs a method of correcting for the spherical aberration. It does this by feeding the...
