EXTINCTION CURVE IN DENSE CORES

very compact cores (n in the range 10^510^7cm3) have been observed in absorption in the isocam maps of the rho ophiuchi main cloud, at 6.75 and 15 mic (abergel et al. 1996). these cores allow to map the spatial variations of the infrared extinction properties of dust grains with the density and the local radiation field. recent submm observations on the balloonborne pronaosspm have demonstrated that such cores are very cold, therefore the grain properties should drastically change inside these cores. we plane to analyse the variations of the silicate extinction features and also to look for the presence of a continum in the extinction curve from 5 to 16.5 mic. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]