The large luminosity of Asymptotic Giant Branch (AGB) stars
 (in most cases from 5 10^3 to 2 10^4 solar luminosity)
 potentially makes them important heating sources of the
 Interstellar Medium (ISM) that surrounds them. Their spectra
 peak at wavelengths larger than 1 micron, and the dominant
 effect is through radiative heating of the large grain
 component of the IS dust.
   The aim of this proposal is to study the effect of the radiative
 heating of IS dust by AGB stars. We propose to map the ISM in
 volumes of ~ 10 cubic parsecs with a typical spatial resolution
 of 0.2 parsecs around sources at a typical distance of 1 kpc
 from the Sun . For this, we will use ISOPHOT with PHT-C100 and
 C60/C90. The fields will have a size of 7 arcmin by 7 arcmin
 and will be centered at 4 arcmin from the heating sources.
   This programme will give new insights on the small scale
 structure of the ISM in very different galactic environments
 (from the disk to the halo) at distances from the Sun ranging
 from 500 pc to 1500 pc, with a spatial resolution of 0.1 to
 0.3 pc. With the proposed sample of 24 AGB sources, we will
 probe the ISM in a total volume of ~ 200 cubic parsecs and
 derive an unbiased evaluation of the ISM filling factor.