FSO performance analysis of a metro city in different atmospheric conditions

In this article, a free-space-optics (FSO) model for a metro city based on real-time visibility data under different weather conditions is presented. Here, the relation between atmospheric attenuation and visibility value and its impact on the FSO performance is carried out. Also, the hybrid-SIM modulation technique is applied for the bit error rate (BER) improvement of the system. Here, Bhubaneswar (the capital of Odisha, India) is considered for the above analysis. The total attenuation, BER, and link margin are calculated for the FSO performance evaluation of Bhubaneswar city and these are simulated using Matlab. The simulation results show that the proposed hybrid-SIM modulation technique achieves about 2.9 dB of SNR improvement than the existing BPSK-SIM technique. Also, from the link margin analysis, it is observed that the sunny day is the most suitable for FSO link transmission. These results can be helpful to decide the FSO parameters and the FSO setup can be designed for any city.

Labor Supply Responses to Learning the Tax and Benefit Schedule

Despite the implications for policy, empirical evidence on the relative importance of factors that shape labor supply responses is missing. This paper helps fill this gap and quantifies the role of information frictions versus other frictions by combining notches in the Norwegian welfare system and quasi-experimental variation in access to information about the slope and location of kinks. While we estimate a frictionless elasticity of 0.3, overall frictions attenuate this elasticity by about 70 percent. We find the information letter increased the earnings elasticity from 0.06 to 0.15, implying that information frictions account for at least 30 percent of total attenuation. (JEL D83, H24, I38, J22, J28, J31)

Climatic Bases and Analysis of Proposed Cloud Attenuation Model for Satellite Links Application

Consistently required lager bandwidth at lower cost induce increases in magnitude of transmission frequency for satellite signal. This is phenomenally accompanied by proportional hydrometeors attenuation. Hence, there is need to evaluate cloud attenuation impact in every climatic region periodically. This report is one of the outcomes of experimental communication research carried out at tropical Ota (6.7oN, 3.23oE) station, southwest, Nigeria. The station spectrum analyzer measures its received beacons total attenuation at 12.245 GHz and elevation angle 59.9o to Astra satellites located at 28.2oE. Daily maximum, minimum and mean temperatures; rain amount, wind speed and direction as well as time of occurrence of each of these weather parameters were also measured. Then the radiometric data including acquired radiosonde data were analysed under rainy and non-rainy conditions, to obtain cloud attenuation contribution from the total attenuation measured per minute. The various data used range in measurement periods between four and fifty-eight years. The outputs were used to compute the station cumulative distributions for the existing cloud models and for the integrated station’s data. Statistical analysis comparing the two cumulative distributions show a high difference between the measured data and existing models’ predicted values. Hence a cloud attenuation computation algorithm and its simulation program were developed and used to derive a new tropical cloud attenuation model. The results of climatic data and analysis were used to justify the well corroborated new cloud attenuation model.

OPTIMIZATION OF DISTRIBUTED STRUCTURES OF ATMOSPHERIC OPTICAL COMMUNICATION NETWORK

Рассмотрены проблемы оптимизации распределенной структуры атмосферной лазерной коммуникационной сети. Поставлена и решена задача оптимизации распределенной атмосферной оптической коммуникационной сети, содержащей один передающий и n приемных узлов. Определено выражение оптимальной связи между дивергенцией луча на входах приемных узлов и расстоянием между передатчиком и этими узлами, при реализации которой суммарное затухание в системе при условии неизменности других факторов, способствующих ослаблению сигнала, достигает минимума. The problems of optimization of the distributed structure of atmospheric laser communication network are considered. The problem of optimization of distributed atmospheric optical communication network containing one transmitting and n receiving nodes is formulated and solved. The formula determining the relation between beam divergence at the input of receiving points and the distance between these points and transmitter is obtained. Technical implementation of this formula brings to a minimum of total attenuation in the system, provided that other factors potentially causing signal attenuation are unchanged.

Radiometric Performance Evaluation of FY-4A/AGRI Based on Aqua/MODIS

Fengyun-4A (FY-4A) is the first satellite of the Chinese second-generation geostationary orbit meteorological satellites (FY-4). The Advanced Geostationary Radiation Imager (AGRI), onboard FY-4A does not load with high-precision calibration facility in visible and near infrared (VNIR) channel. As a consequence, it is necessary to comprehensively evaluate its radiometric performance and quantitatively describe the attenuation while using its VNIR data. In this paper, the radiometric performance at VNIR channels of FY-4A/AGRI is evaluated based on Aqua/MODIS data using the deep convective cloud (DCC) target. In order to reduce the influence of view angle and spectral response difference, the bi-directional reflectance distribution function (BRDF) correction and spectral matching have been performed. The evaluation result shows the radiometric performance of FY-4A/AGRI: (1) is less stable and with obvious fluctuations; (2) has a lower radiation level because of 24.99% lower compared with Aqua/MODIS; 3) has a high attenuation with 9.11% total attenuation over 2 years and 4.0% average annual attenuation rate. After the evaluation, relative radiometric normalization between AGRI and MODIS in VNIR channel is performed and the procedure is proved effective. This paper proposed a more reliable reference for the quantitative applications of FY-4A data.

What Can We Learn from the CloudSat Radiometric Mode Observations of Snowfall over the Ice-Free Ocean?

The quantification of global snowfall by the current observing system remains challenging, with the CloudSat 94 GHz Cloud Profiling Radar (CPR) providing the current state-of-the-art snow climatology, especially at high latitudes. This work explores the potential of the novel Level-2 CloudSat 94 GHz Brightness Temperature Product (2B-TB94), developed in recent years by processing the noise floor data contained in the 1B-CPR product; the focus of the study is on the characterization of snow systems over the ice-free ocean, which has well constrained emissivity and backscattering properties. When used in combination with the path integrated attenuation (PIA), the radiometric mode can provide crucial information on the presence/amount of supercooled layers and on the contribution of the ice to the total attenuation. Radiative transfer simulations show that the location of the supercooled layers and the snow density are important factors affecting the warming caused by supercooled emission and the cooling induced by ice scattering. Over the ice-free ocean, the inclusion of the 2B-TB94 observations to the standard CPR observables (reflectivity profile and PIA) is recommended, should more sophisticated attenuation corrections be implemented in the snow CloudSat product to mitigate its well-known underestimation at large snowfall rates. Similar approaches will also be applicable to the upcoming EarthCARE mission. The findings of this paper are relevant for the design of future missions targeting precipitation in the polar regions.

X-ray scattering from a plane parallel slab using radiation transfer considerations

The X-ray scattering power of a plane parallel homogeneous slab of material is derived using radiation intensity transfer equations. The scattering power scales with the ratio of the scattering coefficient of interest to the total attenuation coefficient. The results can be used to guide the choice of slab thickness, scattering geometry and photon energy to maximize the scattering power in both elastic and inelastic X-ray scattering experiments.