A ballon-borne polarimetric device was developed in 1983 for the purpose of monitoring stratospheric aerosols from limb scannings of the radiance and the polarization of scattered sunlight. The first flight of the experiment was launched on December 15, 1983. A preliminary interpretation of the results has been given previously. The main purpose of this paper is to develop an improved and extended analysis of the data. First, we study how limb observations depend on variations of the solar elevation, particulary with respect to signal contamination by tropospheric light. A simple modeling of this effect is proposed. Comparison of the radiance and polarization measurements allows us to check this model, which may be useful for analyses of limb experiments. Second, variations of the atmospheric transmission as a function of the solar elevation are shown to permit a calibration-free and improved determination of the aerosol slant optical thickness. Finally, Monte Carlo calculations in spherical geometry fix the contribution of multiply scattered light in the signals. These various points allow us to improve the aerosol characteristic retrieval. A very accurate estimate of the particle mean dimension is obtained, some insight is gained about the actual form of the aerosol size distribution, and the particle refractive index is shown to be in the range 1.45¿0.05 around 1000-nm wavelength, which corroborates, from purely passive measurements, the presence of a hydrated sulfuric acid aerosol. ¿ American Geophysical Union 1988