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The payload of the four Cluster spacecraft dedicated to multipoint measurements in the earth’s magnetosphere includes ion emitters that can emit currents up to a few tens of microamperes to partially compensate for the photoemiss...
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The payload of the four Cluster spacecraft dedicated to multipoint measurements in the earth’s magnetosphere includes ion emitters that can emit currents up to a few tens of microamperes to partially compensate for the photoemission current originating at the spacecraft surfaces and thereby achieve a reduction in the spacecraft potential from values often as high as several tens of volts positive to values well below 10 V. This effect is highly desirable to improve on-board particle measurements, especially of electrons, by reducing the photoelectron flux into the sensors and by reducing the distortions of particle trajectories in the spacecraft sheath. On the other hand, a perfectly stable spacecraft potential precludes the utilization of the spacecraft as a plasma probe, including the useful technique to estimate ambient plasma density from the spacecraft potential. This paper shows that the small residual variations of the potential still allow the determination of ambient plasma density, albeit at reduced accuracy. We present an outline of the applied method with examples. In spring 2002, in the cusp region, the Cluster interspacecraft distances were well below 1000 km. For selected intervals, the potentials of controlled and uncontrolled spacecraft are compared, taking advantage of the fact that the ion emitters were not operating on all spacecraft. Special considerations regarding the secondary electron production and its effect on the controlled spacecraft potential were found to be necessary, and examples of this aspect are presented as well. Finally, the effect of the potential control on the double-probe electric field measurements is assessed. It is found that the normal sun-aligned offset of the electric field caused by the asymmetric spatial distribution of photoelectrons around the spacecraft can be affected by the potential control. Nonetheless, the information about plasma density is not lost when active spacecraft potential control (ASPOC) - s applied. This is also relevant for future missions with ASPOC, particularly the NASA Magnetospheric Multiscale mission launched in March 2015. Regular intercalibration of controlled and uncontrolled potentials is nonetheless advisable to increase the reliability of the method.
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Criteria are proposed for evaluating sea surfacetemperature(SST) retrieved from satellite infra-redimagery:bias should be small on regional scales;sensitivity to atmospheric humidity should be small; andsensitivity of retrieved SS...
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Criteria are proposed for evaluating sea surfacetemperature(SST) retrieved from satellite infra-redimagery:bias should be small on regional scales;sensitivity to atmospheric humidity should be small; andsensitivity of retrieved SST to surface temperature should be .close to 1 K K-1.Their application is illustrated for non-linear sea surface temperature(NLSST)estimates.233929observations from the Advanced Very High ResolutionRadiometer(AVHRR)on Metop-A are matched with in situdata and numerical weather prediction(NWP)fields.NLSSTcoefficients derived from these matches have regional biasesfrom—0.5 to+0.3 K.Using radiative transfer modelling wefind that a 10% increase in humidity alone can change theretrieved NLSST by between—0.5 K and +0.1 K.A 1 Kincrease in SST changes NLSST by <0.5 K in extreme cases.The validity of estimates of sensitivity by radiative transfermodelling is confirmed empirically.
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Meteorological satellite and satellite meteorology are the fastest developing new branches in the atmospheric sciences. Today the meteorological satellite has become a key element in the global atmospheric sounding system while th...
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Meteorological satellite and satellite meteorology are the fastest developing new branches in the atmospheric sciences. Today the meteorological satellite has become a key element in the global atmospheric sounding system while the satellite meteorology is covering the main components of earth's system science. This article describes the major achievements that China has made in these fields in the past 30 years. The following contents are involved: (1) History and present status of China's meteorological satellites. It covers the development, launch, operation, technical parameters of China's polar and geostationary meteorological satellites. (2) Major achievements on remote sensing principle and method. It describes the retrieval of atmospheric temperature and humidity profiles, cloud character retrieval, aerosol character retrieval, precipitation retrieval as well as the generation of cloud wind. (3) Achievement on the studies of meteorological satellite data application. This part covers the applications of meteorological satellite data to weather analysis and forecast, numerical forecast, climate monitoring, and prediction of short-term climate change. Besides, the new results on data assimilation, climate monitoring, and forecast are also included.
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This study focuses in building a script that will analyze the condition of natural vegetation in boracay using satellite images through artificial neural network. The designed program is created to help user assess and preserve th...
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This study focuses in building a script that will analyze the condition of natural vegetation in boracay using satellite images through artificial neural network. The designed program is created to help user assess and preserve the area without consuming so much time. The levels of condition were determined as vegetation, Infrastructure, and Water. The researcher constructed the artificial neural network by the help of MATLAB application. With the use of the images gathered from satellite images, the researchers were able to produce result of vegetation, Infrastructure, and water in percentage form.
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This letter presents preliminary results concerning the use of new observations from the A-Train Constellation for testing a new technique of remotely sensing hurricane intensity from space based on modeling a hurricane as a balan...
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This letter presents preliminary results concerning the use of new observations from the A-Train Constellation for testing a new technique of remotely sensing hurricane intensity from space based on modeling a hurricane as a balanced, convectively neutral vortex. The key observational requirements are simultaneous, accurate measurements of cloud-top height, cloudtop temperature, and cloud profiling information across the center of the storm, although there are ways to bypass the need for cloud-top temperature. In this letter, the Moderate Resolution Imaging Spectroradiometer onboard Aqua provides an estimation of the cloud-top temperature, and the near-simultaneous CloudSat observations provide the essential cloud-top height and cloud profiling information. Initial results indicate that the new technique is a promising method for estimating storm intensity when compared post facto to the best track database. Potential uncertainties and room for further refinement of the technique are discussed.
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There is a global consensus that carbon dioxide and other greenhouse gas emissions must be reduced as a response to global climate change. Remote sensing satellite data have become an important means of monitoring carbon emission ...
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There is a global consensus that carbon dioxide and other greenhouse gas emissions must be reduced as a response to global climate change. Remote sensing satellite data have become an important means of monitoring carbon emission due to its unique advantages such as availability, high resolution, and wide coverage, and remote sensing data are playing an increasingly important role in carbon monitoring and fixation. This article summarizes the main applications of remote sensing satellite data in reducing carbon emissions and prospects for future research.
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A micro-piggyback satellite, "μ -LabSat", was launched by an H-IIA rocket on 14 December 2002. μ -LabSat is a bias momentum micro-satellite with two wheels, a configuration that is not normally capable of three-axis attitude man...
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A micro-piggyback satellite, "μ -LabSat", was launched by an H-IIA rocket on 14 December 2002. μ -LabSat is a bias momentum micro-satellite with two wheels, a configuration that is not normally capable of three-axis attitude maneuvers. This paper describes an algorithm that has been developed to enable such maneuvers and presents the results of its evaluation by numerical simulation and in-orbit experiment.
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The multi-objective design of concentric ring antenna arrays for isoflux radiation for Geostationary Earth Orbit (GEO) and Medium Earth Orbit (MEO) satellites is presented in this paper. This design of concentric ring antenna arra...
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The multi-objective design of concentric ring antenna arrays for isoflux radiation for Geostationary Earth Orbit (GEO) and Medium Earth Orbit (MEO) satellites is presented in this paper. This design of concentric ring antenna arrays considers the optimization of the spacing between rings and the amplitude excitation across the antenna elements in order to generate the trade-off curves between the side lobe level (SLL) and the isoflux mask error. In order to use fewer levels of excitations to diminish the hardware complexity, a concentric excitation is considered across the antenna array. Simulation results applying a differential evolution multi-objective (DEMO) optimization method are provided in this document. Furthermore, an analysis of the trade-off curve between the SLL and the isoflux mask error is achieved.
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News editors obtained the following quote from the background information supplied by the inventors:
“There is an ongoing resurgence of satellite communications. Several plans for satellite networks
have been announced in the p...
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News editors obtained the following quote from the background information supplied by the inventors:
“There is an ongoing resurgence of satellite communications. Several plans for satellite networks
have been announced in the past few years. The target services vary, from backhaul and fixed
wireless, to transportation, to outdoor mobile, and to Internet-of-Things (IoT). Satellite networks could
complement mobile networks on the ground by providing connectivity to underserved areas and providing
multicast/broadcast services.
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Precipitation amount (PA), frequency (PF), and intensity (PI) over China are characterized and quantified using a high-resolution merged satellite-gauge precipitation product for 6 years (January 2008 through December 2013). The p...
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Precipitation amount (PA), frequency (PF), and intensity (PI) over China are characterized and quantified using a high-resolution merged satellite-gauge precipitation product for 6 years (January 2008 through December 2013). The precipitation product synthesizes both state-of-the-art multisatellite precipitation algorithms and the latest, densest gauge observations to provide high-quality precipitation information at a very fine temporal and spatial resolution $(text{0.1}^{circ}!/text{hourly})$ that encompasses all of China. The geographical and seasonal variations in precipitation are systematically documented over seven subregions, each corresponding to a unique climate regime. PA, PF, and PI have large seasonal and geographical variations across China. It is found that 1) although heavy precipitation events $({ > } 10 ;text{mm/h})$ represent only 0.8% of total precipitation occurrence over China, they contribute 12.1% of the total precipitation volume. Light precipitation events $({ < } 1 ;text{mm/h})$ dominate the precipitation occurrence (74.3%) and contribute 23.1% of the total precipitation volume; 2) over the high-altitude Tibetan Plateau (TP), the landlocked Xinjiang (XJ) province, and northwestern China (NW), light precipitation events $({ < } 1 ;text{mm/h})$ occur very frequently (74.7%, 82.1%, and 64.1% of all precipitation events) and contribute 29.8%, 35.5%, and 27.4% of the total precipitation volume. This initial continental-scale study provides new insights on precipitation characteristics that can benefit meteorological and hydrological modeling and applications, especially in areas with sparse rain-gauge coverage.
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