Abstract :
The Earth´s atmosphere, particularly the ionosphere and troposphere, often has detrimental effects on the performance of many radio frequency systems. In order to ensure the effective operation, planning, and management of such systems, comprehensive, global, and timely specifications of the atmosphere must be obtained; this includes detailed observations of the refractivity profiles of the aforementioned regions. Ionospheric refractivity information can be accurately acquired by employing an assimilation system; 3D images of the ionosphere can be produced using data gathered from a range of measurement techniques, such as GPS receivers and ionosondes.