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Wave optics algorithms are applied for processing radio occultation data, especially in the lower troposphere in order to reconstruct the geometric optical ray structure of the wave field. Wave field diffracted by strong inhomogeneities in the lower troposphere and by long propagation distance from the planet limb to the space-borne receiver has a complicated structure. Its amplitude and phase are...
This paper shows that it is possible to retrieve the radio field near the atmosphere from a radio field known at some interface outside the atmosphere by using radio holographic vector equations. To use these equations a reference signal is needed to derive the field distribution from radio holograms. The reference signal coincides with the Green function of the back-propagated field and can be found...
This paper estimates accuracy of the open loop tracking of the tropospheric radio occultation signals by means of numerical simulations. Each error source, such as: downsampling and integration in receiver, thermal noise, the up-sampling in postprocessing, deviation of the mean frequency of the sampled signal from zero, the length of the recorded signal, pseudo random modulation, is studied separately...
This paper investigates the limitations imposed by the receiver on the accuracy of the Fourier techniques related to radio occultations in the Earth atmosphere. These limitations are related to sampling frequency and signal-to-noise ratio, as well as diffraction. The impact of each of these limiting factors are discussed and analysed in terms of measurement accuracy and resolution. A main result is...
In the present work, we study a canonical transform that directly maps the measured field to the impact parameter representation without first carrying out a back-propagation. This canonical transform is determined to first order in a small parameter that measures the deviation of the satellite orbit from a circle. When the parameter is equal to zero, i.e., for circular orbits, our canonical transform...
We have analyzed radio occultation simulations containing atmospheric multipath behavior. In the case where the medium and the satellite orbits are spherically symmetric the multipath behavior can be unfolded by a Fourier transform of the measured signal. However, small deviations from circular orbits may imply that the multipath behavior cannot be completely unfolded due to the fact that a given...
Occultation geometry under a spherical symmetry assumption leads to models described by the Abel integral equations. Analyzing general properties of the Abel transform, this work derives practical rules for discretization and for solution of the inverse problems, containing Abel-type integral equations. Two applications in remote sensing are considered: reconstruction of local densities from horizontal...
Stellar occultation technique provides global measurements of the atmospheric composition with a high vertical resolution. The main interest of the GOMOS (Global Ozone Monitoring by Occultation of Stars) instrument is to measure ozone density at 10–100 km. The correlations between the cross sections of ozone, neutral density and aerosols are rather strong in the UV/visible wavelength region, which...
An alternative remote sensing technique for the retrieval of atmospheric refractive index profiles is presented. It is an optimization procedure for the inversion of ground-based GPS phase measurements collected at low elevation angles. The Abel inversion, usually adopted to infer atmospheric profiles from space-based radio occultation observations, cannot be applied to the inversion of ground-based...
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