Solar System objects
Improved models of asteroids: Thermophysical model (Müller et al 1998) ?MID IR photometry needed to derive precise light curves)
ISO has revealed the presence of crystalline silicates (emission at 9-11 mm) in many comets.
Planets: a lot of new spectroscopic information, with unprecedented resolution, molecular bands in the MID IR are observed in full detail.
No new information about spatial distribution