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We have studied several optical systems for dust velocity measurements on a cometary orbiter using light scattering to detect particles. Two main concepts are considered. The first relies on trajectory imaging, while the second uses time-of-flight measurements between two or more light sheets. Their merits and disadvantages are discussed. The favored system, time-of-flight between two planes with particle localization, is described.
The conceptual design for an optical instrument capable of characterizing dust particles by in situ measurements is described. This instrument, the Integrated Dust Analyzer (IDA), measures the light scattered at several different angles as a particle passes through a pair of polarized light curtains. It is capable of defining or providing an indication of such characteristics as size, index of refraction, absorptivity, and aggregate structure.
We have set up an experimental device to optically study the scattering properties of dust particles. Measurements over the 8 — 174° interval of scattering angles are performed on a continuously flowing dust loaded jet illuminated by a polarized red HeNe laser beam. The scattering is averaged over the population of the dust particles in the jet, which can be determined independently, and give the “volume scattering function” for the two directions of polarization directly. While results for spherical particles are in good agreement with Mie theory, those for arbitrary particles show conspicuous deviations.
This contribution will attempt to give a coherent and up-to-date view of the interplanetary dust cloud as well as to delineate some of the current outstanding problems. It is largely based on studies carried out at Laboratoire d’Astronomie Spatiale during the past years.
Ferroelectric epitaxial Pb(Zr,Ti)O3 (PZT) layers were grown by pulsed laser deposition on SrTiO3/GaAs templates fabricated by molecular beam epitaxy. The templates present an excellent structural quality and the SrTiO3/GaAs is abrupt at the atomic scale thanks to surface Ti pre-treatment. The PZT layers contain a- and c- domains, as shown by X-Ray diffraction analyses. Piezoforce microscopy experiments and macroscopic electrical characterizations indicate that PZT is ferroelectric. A relative dielectric permittivity of 164 is extracted from these measurements.
We used total solar eclipse free of parasitic light for studying the prominence to corona interface, and the corresponding cavity in the context of the coronal physics. We analysed the visible continuum between the prominences to directly look at the electron density. We demonstrate some enhanced heating in the cavity region. Some similarities with the interface regions are shown: the photosphere to the chromosphere and the prominence to the corona interface. The optically thin neutral Helium at 4713 Å and the singly ionized Helium 4686 Å Paschen α lines are considered. We summed 80 slitless visible eclipse flash spectra that we compare with simultaneously obtained EUV SWAP/Proba2 174 Å images of ESA and AIA/SDO 171Å 193 Å 304 Å and 131 Å filtergrams. Intensity profiles in a radial direction are studied. We deduce the variation of the intensity ratio I(He I 4713) / I(He II 4686). Discussion: the temperature rises at the edge of the prominences. We evaluate for the first time with spectrophotometric accuracy the continuum modulations in prominence spectra. W-L intensity deficits are observed near the prominence boundaries in both eclipse spectra and in EUV images, confirming that the prominence -cavity regions correspond to a relative depression of plasma density of the surrounding corona. Conclusion: we demonstrate some enhanced heating occurring in these regions assuming hydrostatic equilibrium.
Applications have been received from Dr. Peter Wheatley (proposed by UK), Prof. Harald Schuh (proposed by Austria), and Dr. Busaba Kramer (proposed by Thailand). All applications were endorsed, with the caveat that Dr. Kramer's application needs to be endorsed by at least one of the other commissions since she has not a publication record in our field.
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