Radio holographic principle for observing natural processes in the atmosphere and retrieving meteorological parameters from radio occultation data

Abstract

The radio holographic principle is briefly described and tested by using radio occultation data of the GPS/MET and MIR/GEO experiments. Sub-Fresnel spatial resolution ∼12 m/pixel was achieved using focused synthetic aperture radio holographic approach, and direct evidence of multibeam propagation effects in the atmosphere was obtained. The achieved instrumental accuracy in angular distance measurements was near 0.004 milliradian/pixel, and observed angular distance between different rays was equal to 0.3 milliradians. The angular resolution of the radio holographic method depends on the wavelength as λ 1 compared to λ 1/2 in conventional methods. In general case the principal limit of the vertical resolution may be determined using focused synthetic aperture antenna theory and may achieve a value ∼20-40 m under assumptions of spherical symmetry and quiet atmospheric conditions. Wave structures were discovered in the altitude distribution of the gradient electron density at a height interval of 60-95 km with spatial period 1-2 km and vertical resolution 300-500 m. Good correspondence was found between the temperature profiles revealed by radio holographic analysis and those obtained by traditional retrieval using UCAR GPS/MET data.

Backpropagation Processing of GPS Radio Occultation Data

“…In recent years, a number of "radioholographic" methods have been proposed that not only aimed to resolve the multipath problem encountered by the standard method but also to improve the vertical resolution of the retrievals [7,8,9,10,11,12]. These methods use both the amplitude and phase of the received signal in reconstructing the ray structure of the refracted field.…”

Observation of wave structures in the upper atmosphere by means of radio holographic analysis of the radio occultation data

“…3 indicates that the amplitude data are more sensitive to high spatial frequency components in the refractive index while the phase excess data are more sensitive to low frequency components. The vertical gradient of electron density may be retrieved from the amplitude data by a method which has been described by Igarashi et al (2000). The results of the restoration dNe(H)/dH for events 0447 and 0158 are shown in Fig.…”

“…The measured angular spectrum may be projected along the rays in the plane PGO on the line DD' (Fig.l) and the distribution of the radio brightness on the Earth's limb as seen from the LEO orbit may be obtained. Thus radio holography may reveal the origin of each ray in the angular spectrum (the point of exit of the ray from the ionosphere) with high angular and spatial accuracy (Igarashi et al, 2000). This is important because the rays arising due to ionospheric irregularities in the F-layer of the ionosphere may be identified and then excluded by an appropriate filtration method (Hocke et al 1999).…”

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ABSTRACTA radio holographic approach, developed by Pavelyev (1998), Hocke et al (1999), Igarashi et al (2000), is applied to observation of wave phenomena in the upper atmosphere using Global Positioning System -"Microlab-l" satellite (GPS/MET) radio occultation data. In the current state the radio holography approach uses the radar focused synthetic aperture principle to obtain high spatial resolution, and to remove the interference part corresponding to scattering from the upper ionosphere.

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Application of the locality principle to radio occultation studies of the Earth's atmosphere and ionosphere

“…The success of these missions demonstrated that the RO technique is a powerful remote sensing tool for obtaining key vertical profiles of bending angle, refractivity, temperature, pressure and water vapour in the atmosphere and electron density in ionosphere with global coverage, high spatial and temporal resolution . Explicit analysis of experimental data of LEO missions introduced important contributions in the following areas: (i) the theory of radio wave propagation (Gorbunov and Gurvich, 1998a;Gorbunov et al, 2002;Benzon et al, 2003;Gorbunov and Lauritsen, 2004;Gorbunov and Kirchengast, 2005;Pavelyev et al, 2004Pavelyev et al, , 2010a; (ii) climate changes detection Steiner et al, 2001;Foelsche et al, 2008); (iii) space weather effects and ionosphere monitoring (Rius et al, 1998;Jakowski et al, 2004;Wickert et al, 2004;Arras et al, 2008Arras et al, , 2010; (iv) deriving new radio-holographic methods of the RO remote sensing (Karayel and Hinson, 1997;Mortensen and Hoeg, 1998;Pavelyev, 1998;Gorbunov and Gurvich, 1998b;Mortensen et al, 1999;Hocke et al, 1999;Sokolovskiy, 2000;Sokolovskiy et al, 2002;Gorbunov, 2002a, b;Gorbunov et al, 1996Gorbunov et al, , 2002Gorbunov et al, , 2010Igarashi et al, 2000;Jensen et al, 2003Jensen et al, , 2004Pavelyev et al, 2002Pavelyev et al, , 2004Pavelyev et al, , 2010aPavelyev et al, , b, 2012Liou et al, 2010;.…”