The relatively recent development of inexpensive, high-speed computati
onal resources has made computerized tomography a readily accessible t
ool for remote sensing. A variety of geophysical remote applications h
ave made use of the technique; in particular, tomography has been used
to image the electron density in the Earth's ionosphere. As in most c
ases there are problems unique to the application. A review of the alg
orithms used to date is presented with a sampling of experimental resu
lts. (C) 1994 John Wiley and Sons, Inc.