High-resolution thermal infrared imaging of the sun: A pipe dream?

I discuss the desired characteristics of an instrument to study the Sun in the 3-20 mu m thermal infrared. I show that even the largest apertures under consideration for a next generation " Advanced Solar Telescope" fall short of the capabilities needed at the long wavelengths. I conclude that the design of AST should not be driven by access to the thermal infrared. Instead the IR would be better served by a special-purpose instrument; even a simple-perhaps temporary-modification of an existing or planned nighttime telescope.