DPS 2001 meeting, November 2001
Session 62. Laboratory Studies
Oral, Chairs: R. Wu, R. Hudson, Saturday, December 1, 2001, 4:40-5:50pm, Regency GH

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[62.02] Systematic Study of the Light Scattering by Aggregates Using Microwave Analog Experiments and Multifactor Analysis

L. Kolokolova, B. A. S. Gustafson (University of Florida)

The unique microwave-analog-to-light-scattering facility at the University of Florida was used to survey light scattering characteristics of aggregated particles. Microwave analog experiments are the fastest and most flexible means to simulate light scattering by complex cosmic dust particles. This remains true although powerful computer codes to calculate light scattering by irregular and inhomogeneous particles have been developed in recent years. Aggregates of a variety of physical characteristics (number and size of constituent particles, packing factor) were built and the scattering was measured at a variety of orientations (to simulate random orientation) and across a range of wavelengths (to study spectral properties). To satisfy the requirements of the statistical multi-factor analysis, known as 2k factorial design, each of three characteristics of an aggregate (number and size of particles, aggregate packing factor) could take two fixed values. In each new experiment only one characteristic differed from those in the previous experiment. Thus, eight (23) aggregates of all possible combinations of two values of three parameters were studied. The values of the characteristics were: 1000 and 5000 for the number of particles in the aggregates; the particle size corresponded to 0.25 and 0.5 micron; the packing factor (the ratio of the total volume of the particles to the volume of the aggregate) was 10 and 50%. The angular and spectral dependencies of intensity and polarization were obtained for these aggregates. The subjects of the statistical analysis were color, polarization and polarimetric color around the scattering angle 90 degree. The statistical analysis showed that the intensity and polarization are mostly affected by the size of the constituent particles. The size also determines the shape of the angular and spectral dependencies and, consequently, the color and polarimetric color. The packing factor and number of the particles have less influence on the light-scattering characteristics within the range studied.

NASA supported this work through grants NAG5-8944 and NAG5-6378.

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