نتایج جستجو برای: occultation
تعداد نتایج: 1773 فیلتر نتایج به سال:
In this paper we present results from analysis of GPS/MET occultation data obtained from the University Corporation for Atmospheric Research database. We have used High-Rate occultation data to study the performance of an earlier 4D ionospheric electron content model|obtained tomographically with the use of the GPS constellation|with satisfactory results. In addition, we have processed UCAR Lev...
In this study different approaches based on multilayer perceptron neural networks are proposed and evaluated with the aim to retrieve tropospheric profiles by using GPS radio occultation data. We employed a data set of 445 occultations covering the land surface within the Tropics, split into desert and vegetation zone. The neural networks were trained with refractivity profiles as input compute...
The NOMAD instrument has been designed to best fulfil the science objectives of the ExoMars Trace Gas Orbiter mission that will be launched in 2016. The instrument is a combination of three channels that cover the UV, visible and IR spectral ranges and can perform solar occultation, nadir and limb observations. In this series of two papers, we present the optical models representing the three c...
The serendipitous detection of stellar occultations by Outer Solar System objects is a powerful method for ascertaining the small end (r . 15 km) of the size distribution of Kuiper Belt Objects and may potentially allow the exploration of objects as far out as the Oort Cloud. The design and implementation of an occultation survey is aided by a detailed understanding of how diffraction and obser...
The characteristics of the populations of objects that inhabit the outer solar system carry the fingerprint of the processes that governed the formation and evolution of the solar system. Occultation surveys push the limit of observation into the very small and distant outer solar system objects, allowing us to set constraints on the structure of the Kuiper belt, Scattered disk and Sedna popula...
In this study a nonlocal, linear observation operator for assimilating radio occultation data is evaluated. The operator consists of modeling the excess phase, that is, integrating the refractivity along straight lines tangent to rays, below a certain height. The corresponding observable is the excess phase integrated through the Abel-retrieved refractivity, along the same lines, below the same...
In this study we have proposed a method based on neural networks to retrieve refractivity, temperature, pressure and humidity profiles by using FORMOSAT-3/COSMIC GPS radio occultation data. To overcome the constraint of an independent knowledge of one atmospheric parameter at each GPS occultation, we trained three neural networks with refractivity profiles as input computed from the geometrical...
The occultation of background stars by foreground Solar system objects, such as planets and asteroids, has been widely used as an observational probe to study physical properties associated with the foreground sample. Similarly, the gravitational microlensing of background stellar sources by foreground mass concentrations has also been widely used to understand the foreground mass distribution....
Remote sensing plays a key role in monitoring the atmosphere, which becomes increasingly important for the Earth’s changing environment. The stellar occultation technique is a novel method to monitor vertical distribution of ozone and other trace gases from the troposphere to the upper mesosphere. GOMOS (Global Ozone Monitoring by Occultation of Stars) flying on board the European Space Agency’...
Introduction Occultation methods based on effects connected with the refraction of electromagnetic waves in both the optical and radiofrequency domains have been used by astronomers for numerous investigations of planetary atmospheres over the last decades. The first experiment started with the Mars flyby by Mariner-IV in 1964. Since this first attempt, radio-occultation experiments have been c...
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