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Levasseur-Regourd A.C. Cabane M. Haudebourg V. Worms J.C. 《Earth, Moon, and Planets》1998,80(1-3):343-368
Most of our knowledge on heterogeneous media in the Universe comes from the light they scatter. This light is mainly linearly
polarized, and the polarization phase curves contain information about the properties of the scattering dust. In the solar
system, the dust seems to be made of irregular aggregates with a size greater than a few microns and a fractal structure.
Many constraints appear in the scattering computations, due to the trickiness of the mathematical calculations, and to our
ignorance of the precise structure of the dust. This leads to the necessity to perform light scattering measurements on characteristic
aggregates, built under low velocity ballistic collisions. Microgravity is a sensible way to achieve such measurements on
a cloud of levitating and aggregating dust particles. A first step has been the PROGRA2 experiment, which operates during parabolic flights on an aircraft. The instrument is a polar nephelometer measuring successively
the light scattered by a dust sample at various angles; it is fully operational, and will provide a data base of polarization
phase curves. A second step is the CODAG-SR experiment, which uses the duration of a rocket flight to build up dust aggregates.
The instrument measures simultaneously the light scattered at numerous phase angles; it is now space qualified, and should
provide in a near future a monitoring of the intensity and polarization phase curves while the aggregation processes are taking
place.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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E Hadamcik J.B RenardA.C Levasseur-Regourd J.C Worms 《Planetary and Space Science》2002,50(9):895-901
In order to interpret polarimetric remote observations of solar system dust clouds (e.g. cometary coma dust), laboratory measurements are needed. Three samples composed of aggregates are studied: crystallized enstatite, pyrogenic alumina and titanium oxide. The new version of the PROGRA2 instrument allows to obtain polarimetric images of the samples under levitation. The dependence of polarization with phase angle and particle size is studied, as well as the effect of the porosity of the particles. Values of polarization at small phase angles are also discussed. The polarization near 90° decreases when the agglomerate size increases and when the porosity increases. 相似文献
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