2-DIMENSIONAL MAPPING OF THE PLASMA-DENSITY IN THE UPPER-ATMOSPHERE WITH COMPUTERIZED IONOSPHERIC TOMOGRAPHY (CIT)

Tomographic imaging of the ionosphere is a recently developed techniqu e that uses integrated measurements and computer reconstructions to de termine electron densities. The integral of electron density along ver tical or oblique paths is obtained with radio transmissions from low-e arth-orbiting (LEO) satellite transmitters to a chain of receivers on the earth's surface. Similar measurements along horizontal paths can b e made using transmissions from Global Position System (GPS) navigatio n satellites to GPS receivers on LEO spacecraft. Also, the intensities of extreme ultraviolet (EUV) emissions can be measured with orbiting spectrometers, These intensities are directly related to the integral of the oxygen ion and electron densities along the instrument line of sight, Two-dimensional maps of the ionospheric plasma are produced by analyzing the combined radio and EUV data using computerized ionospher ic tomography (CIT), Difficulties associated with CIT arise from the n onuniqueness of the reconstructions, owing to limited angle measuremen ts or nonoptimal receiver location. Improvements in both reconstructio n algorithms and CIT measurement systems are being implemented to over come these difficulties. New imaging systems being developed employ CI T for large area mapping of the plasma densities in the ionosphere, (C ) 1998 American Institute of Physics.