Laboratory measurements of the brightness and linear polarization of the light scattered by clouds of particles are necessary to interpret remote sensing measurements of dust in space and in planetary atmospheres. For 30 years, such laboratory measurements were conducted by the PROGRA2 project for particles with different natures, sizes and shapes. The resulting database contains the brightness and linear polarization curves for 170 samples and at 4 wavelengths in the visible and near infra-red domains. The samples cover most of the particles that we expect to find in space and in planetary atmospheres. The particles can be compact, porous or aggregated, with sizes up to hundreds of µm; the monomers of aggregates can have sizes as small as 10 nm. The measurements were obtained for clouds of randomly oriented particles levitated on the ground conditions by an air draught technique, and under microgravity conditions during parabolic flights. Complementary measurements were obtained for deposited particles in layers to compare the main characteristics of the phase curves using the same sample. After a description of the instruments and of the samples under study, we present the database and the main results already obtained with PROGRA2. The phase curves often differ for deposited and levitating particles. Such phase curves are related to different physical properties of the particles, and can be compared to modelling calculations. In case of agregated particles, we discuss the influence of the monomers on the phase curves. Finally, the main results obtained for dust analogs of differents object of the solar system are compared to observations.

中文翻译：

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实验室 PROGRA2 数据库用于解释云和层中固体颗粒散射光的线性偏振和亮度相位曲线

实验室测量粒子云散射光的亮度和线性偏振对于解释太空和行星大气中灰尘的遥感测量是必要的。 30 年来，PROGRA2 项目一直在对不同性质、尺寸和形状的颗粒进行此类实验室测量。生成的数据库包含 170 个样本以及可见光和近红外域 4 个波长的亮度和线性偏振曲线。这些样本涵盖了我们期望在太空和行星大气中发现的大部分粒子。颗粒可以是致密的、多孔的或聚集的，尺寸可达数百微米；聚集体的单体尺寸可小至 10 nm。这些测量是通过气流技术在抛物线飞行期间在微重力条件下悬浮在地面条件下的随机定向粒子云获得的。对层状沉积颗粒进行了补充测量，以比较使用相同样品的相位曲线的主要特征。在描述了所研究的仪器和样本之后，我们介绍了数据库以及使用 PROGRA2 获得的主要结果。沉积颗粒和悬浮颗粒的相曲线通常不同。这种相曲线与颗粒的不同物理性质有关，并且可以与建模计算进行比较。对于聚集颗粒，我们讨论单体对相曲线的影响。最后，将太阳系不同天体的尘埃类似物获得的主要结果与观测结果进行了比较。