A newly adapted horizon-scanning technique can simultaneously monitor the vertical distribution of aerosols, as well as ozone and neutral atmospheric density, in the stratosphere and mesosphere for both meteorological and ecological application in a global satellite-monitoring program. The horizon-inversion technique permits the conversion of scattered solar-radiation horizon (limb) profiles into the vertical distribution of aerosol extinction coefficients. Results are given based on real and simulated experimental data which indicate that the aerosol layers can be identified and that the potential exists for estimating the physical characteristics of aerosols within a layer. TRATOSPHERIC distributions of aerosols have been drawing increasing attention as a result of new knowledge concerning their role in the Earth's radiation balance. These particles are now known to cause temperature changes both in the stratosphere and at the Earth's surface. Of particular interest is the aerosol vertical distribution which is influenced both by man-made environmental pollutants and by natural phenomena. This paper describes a mathematical technique of horizon- radiance inversion developed to recover the vertical distribu- tion of aerosol extinction and, coincidentally, ozone and neu- tral atmospheric density in the stratosphere and mesosphere.l The technique provides for the inversion of horizon-intensity profiles obtained by scanning the Earth's sunlit horizon with a satellite-borne sensor. In this experimental configura- tion, a satellite-base d sensor with a limited field of view mechanically scans the Earth's horizon (Fig. 1) in a multispec- tral mode, allowing the aerosols to be distinguished from other atmospheric constituents, such as the neutral atmosphere and ozone. The sensor output is inverted by applying a Kalman-Bucy recursive filter to the received signal, using a reference-intensity profile generated by a theoretical radia- tive-transfer simulation. When the scattering or absorption cross sections are well known (as in the case of ozone and the neutral atmosphere), the received multispectral signals are inver- ted to yield constituent-density information. When the cross sections are not well known, however—as in the case of aerosols—the extinction profile is obtained directly from the inversion. Further development of this horizon-inversion