Ionospheric Research with Satellites

Abstract

The existence of an ionized environment of the Earth’s atmosphere is known since the beginning of the twentieth century. In 1901, the Italian scientist Guglielmo Marconi (1874–1937) astonished the world by successfully transmitting radio signals across the Atlantic. In 1925, Edward Victor Appleton (1892–1965) in England experimentally verified the existence of a conducting layer above the Earth’s surface that reflects radio signals. This layer, the ionosphere, is composed of ions and electrons, and the reflection is due to the interaction of the electrons with the electromagnetic fields of the radio waves. For the verification of the ionosphere’s existence, Appleton was awarded the 1947 Nobel Prize in physics, just as Marconi, who had been awarded in 1909. The first knowledge of the ionosphere was based on radio sounding of the upper atmosphere. But the waves emitted from the ground arrive only at a certain height because they cannot go beyond the “reflection peak” of the ionosphere, the layer located at about 300 km, where the electron density is maximum.