Atmospheric extinction related to aerosol mass concentration and meteorological conditions in the atmosphere of Qena (Egypt)

The dependence of the atmospheric extinction on aerosols concentration, temperature and wind speed is demonstrated. The atmospheric extinction was determined by measuring the transmission loss of radiation from alight source across 36 cm path with a photocell detector Conclusion include a general association of high extinction with high aerosols concentration, temperature and wind speed, but there are no one-to-one relationships. A correlation study between the extinction coefficient and each of these parameters was performed.

Quantum communications in a moderate-to-strong turbulent space

Since the invention of the laser in the 60s, one of the most fundamental communication channels has been the free-space optical channel. For this type of channel, a number of effects generally need to be considered, including diffraction, refraction, atmospheric extinction, pointing errors and, most importantly, turbulence. Because of all these adverse features, the free-space channel is more difficult to study than a stable fiber-based link. For the same reasons, only recently it has been possible to establish the ultimate performances achievable in quantum communications via free-space channels. Differently from previous literature, mainly focused on the regime of weak turbulence, this work considers the free-space optical channel in the more challenging regime of moderate-to-strong turbulence. This regime may occur in long-distance free-space links on the ground, in uplink to high-altitude platform systems (HAPS) and, more interestingly, in downlink from near-horizon satellites. In such a regime we rigorously investigate ultimate limits for quantum communications and show that composable keys can be extracted using continuous variable quantum key distribution. In particular, we apply our results to downlink from satellites at large zenith angles, for which not only turbulence is strong but also refraction causes non-trivial effects in terms of trajectory elongation.

Generalised Trends In Atmospheric Attenuation And The Importance of Accurate Extinction Calculation

The purpose of this literature review is to explore and quantify the causes of attenuation of electromagnetic radiation, as well as to develop generalized trends for extinction as a function of influential factors (wavelength of incident electromagnetic wave, altitude of observatory, variations in seasons). This literature review also discusses the implications of precise measurement of atmospheric attenuation in determining intrinsic luminosity of stars in astronomical photometry and significance of accurate measurement for atmospheric extinction to precisely calculate the mass, size and lifetime of stars in the main sequence of the Hertzsprung-Russell plot diagram.