Characterization of the DUSTER instrument for stratospheric dust collection and Raman analysis of stratospheric samples
De Angelis, Simone (2011) Characterization of the DUSTER instrument for stratospheric dust collection and Raman analysis of stratospheric samples. [Tesi di dottorato] (Inedito)
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The direct collection of cosmic interplanetary dust in the Earth stratosphere is a unique tool for the understanding of the structure, formation and evolution of our planetary system; the collection and study of rare interstellar grains, that penetrate in terrestrial stratosphere (Grun et al., 2001), can give insights about the interaction of the Solar System and its neighbourhood, the Local Interstellar Medium. Global atmospheric dynamics causes air masses to descent from the mesosphere to the stratosphere, in correspondence of the polar vortex (Russell et al., 1993), hence extraterrestrial particles that enter the Earth atmosphere can reach the stratosphere where they settle gravitationally. The terrestrial stratosphere (from an altitude of 15 to 50 km) is a suitable environment where to collect extraterrestrial samples, especially the upper stratosphere, above 25-30 km of altitude: it is close to the frontier between the Earth and the space, easily reachable thanks to stratospheric balloons. In the upper stratosphere the contamination due to terrestrial material is minimum, and the concentration of cosmic particles is increased of about one million, with respect to the concentration in space. The various populations of interstellar dust grains and interplanetary dusts, their sources and properties are described in the chapter 1. The collection of IDPs in the range 10-100 micrometers on board NASA U2 aircrafts at an altitude of 20 km and on board stratospheric balloons has been performed in the past decades, so IDPs in this size range have been largely studied (see the chapter 2 for a brief review of sampling return experiments in stratosphere); on the other side IDPs in the sub-micron and micrometer range are poorly studied; small IDPs suffer a lower flash heating during the atmospheric entry, and moreover they are the most abundant in the size distribution. The study of interplanetary dust particles can help to solve scientific questions not also in planetology, or in astrophysics; their study is relevant for the astrobiology and for the atmospheric sciences. The DUSTER project (Dust in the Upper Stratosphere Tracking Experiment and Retrieval) has been designed and realized to collect refractory dust particles in the sub-micrometer and micrometer range in the upper stratosphere, with the aim to collect cosmic dust particles (Palumbo et al., 2008; Della Corte et al., 2011). In the chapter 2 the different populations, terrestrial and extraterrestrial, of stratospheric aerosols are described. Collected samples are then analyzed in laboratory with several techniques, using scanning electron microscope (SEM), field-emission scanning electron microscope (FESEM), energy dispersive X-rays (EDX), infrared spectroscopy (Ciucci et al., 2011), micro-Raman spectroscopy (De Angelis et al., 2011). Transmission electron microscope (TEM) and isotopic analyses are also planned for the future. Differently from other sampling return experiments, the DUSTER project reduces the steps of manipulation of collected samples in the laboratory; the samples are indeed analyzed at the electron microscope directly on the collection substrates. The sampling on board stratospheric balloons is non-destructive and non-contaminant, respect to the collection on board aircrafts. The DUSTER instrument and the various measurements and tests performed are described in the chapter 3. In the chapter 4, the calibration of DUSTER, consisting of collection efficiency performance measurements, performed at the Cosmic Physics Laboratory of the Applied Sciences Department, ''Parthenope'' University of Naples, are described. Finally, in the chapter 5, micro-Raman analyses on samples collected during the DUSTER-2008 flight campaign (from Svalbard Islands, Norway), are explained. Moreover, a NI-LabVIEW tool, developed for the automatized compute of fits of numerous Raman spectra, is presented.
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