We will attempt mapping at 15 microns of the detached circumstellar
 shells around the carbon stars U Ant and S Sct. The main goal is
 to explore the distribution of dust in the shell, determine its
 inner and outer radius and see whether it shows the same type of
 clumps as those seen in CO J=1-0 and 2-1 lines. The result will
 illuminate the origin of these shells and the mass loss
 mechanism in general.