Results of the PROGRA(2) experiment: An experimental study in microgravityof scattered polarized light by dust particles with large size parameter

The PROGRA(2) experiment allows measurements under microgravity conditions of polarization phase curves for clouds of dust particles. The sizes that c an be used range from a few micrometers to hundreds of micrometers; regular or irregular particles can be tested. Measurements obtained on compact par ticles of boron car bide and silicon carbide are presented. Results for the silicon carbide, obtained for different values of the number densities of the particles, indicate that values of the polarization maximum are lower w hen measured under microgravity conditions than on the ground. Although sti ll not fully demonstrated, this result could be used to understand why it h as been difficult to correlate measurements of the positive branch of the p olarization phase curve done on the ground with actual data on Solar System objects, (C) 1999 Academic Press.