Infrared remote sensing provides a means for radiometry of hot volcanic features. Previously, two spectral band measurements have been combined to solve simple 2-component models of lava surface temperatures. However, pixel dimensions often exceed the widths of lava bodies. In such cases, 3-component models are more realistic. Here, a procedure for solving such a model from three infrared observations is presented. It is then demonstrated using Thematic Mapper Simulator data recorded over Mount Etna, Italy, in 1991. By constraining temperatures and pixel-filling fractions of the three different thermal components in this way, improved estimates of radiant emittance can be obtained. The techniques described could be applied to satellite data of volcanic, and other, hot spots (including fires). ¿ American Geophysical Union 1993