Satellite Remote Sensing by the Technique of Computed Tomography

Abstract

Computed tomography is a medical diagnostic technique in which x-ray transmission measurements at numerous angles through the human body are processed by computer to produce cross-sectional pictures of the body. A modification of this technique, using emitted infrared or microwave radiation instead of transmitted x-ray radiation, can be applied to satellite radiance measurements taken along the orbital track at various angles. Cross sections of the vertical atmospheric temperature structure (or the gaseous constituent density structure) are retrieved from the collection of radiance measurements taken at various angles and frequencies. The advantage of this technique over conventional remote sensing methods is the additional information acquired by viewing a given point in the atmosphere at several angles as well as at several frequencies. The physical and geometric concepts involved are discussed along with the mathematical formulation of the problem and the practical aspects of applying the technique. A method of solution of the resulting large, sparse system of equations is given and is applied to simulated case studies. Temperatures retrieved by the computed tomography technique, when compared with those retrieved by conventional methods, showed an overall average improvement in accuracy of as much as 34% in the study.