First application of the radioholographic method to wave observations in the upper atmosphere

Abstract

[1] Wave phenomena in the upper atmosphere can be studied using the high-precision Global Positioning System (GPS) radio navigational field. In this paper, basic principles, accuracy, and vertical resolution of the radioholographic technique for studies of ionospheric wave phenomena are presented for the general case when the orbits of the satellites are arbitrary. Results of testing of the radioholographic method are discussed using orbital station MIR and geostationary satellites (MIR/GEO) and GPS/Meteorology (GPS/MET) radio occultation data. The radioholographic method has high vertical (12-30 m) and angular (4-8 mrad) resolution, which has been validated by directly observing multibeam propagation in the atmosphere and revealing signals, reflected from the sea, in GPS/MET and MIR/GEO radio occultation data. We show that this method allows one to determine the vertical profile of the electron density and monitoring wave structures in the upper atmosphere. As an example of this approach, observations of the summer Antarctic mesosphere on 7 February 1997 are presented. We show, by combining phase and amplitude analysis, that a vertical resolution of 0.3-0.5 km reveals wavelike structures with spatial periods from 1-2 km to 8-10 km in the vertical electron density distribution in the D and E regions. Variations in the gradient of the electron density from ±5 Â 10 3 to ±8 Â 10 3 el/(cm 3 km) at altitudes of 72-95 km were observed. The obtained results demonstrate the high-technology level of the radioholography approach and open new perspectives for radio occultation experiments: measurements of the characteristics of the natural processes in the atmosphere, mesosphere, and ionosphere and observations of the state of the sea surface by measuring parameters of reflected signal simultaneously with radio occultation experiments.

GPS radio holography as a tool for remote sensing of the atmosphere, mesosphere, and terrestrial surface from space

“…Equation (11) describes the angular spectrum of the radio field A(b(x),p(x)) as a function of ray coordinates b and p. The second and third parts of Eq. (11) permit an independent measurement of the impact parameters p, p m and refraction angles n(p), n(p m ) corresponding to each ray in the angular spectrum A(b,p) (Hocke et al 1999;Igarashi et al 2000;Pavelyev et al 2002aPavelyev et al , 2002b. From a formal point of view, there is a similarity between Eqs.…”

“…Usually the phase data are used to retrieve vertical profiles of the refraction index, temperature in the atmosphere, and electron density in the ionosphere with a vertical resolution of about the size of the Fresnel zone (~0.2-1.0 km). This apparently is why measurements of vertical gradients in the atmosphere and lower ionosphere (a height interval from 50 to 120 km) have not been used in most RO work, with some rare exceptions (Vorob'ev et al 1999;Sokolovskiy 2000;Igarashi et al 2000Igarashi et al , 2001Pavelyev et al 2002aPavelyev et al , 2002b. Also, reflections from the Earth's surface have not been considered in GPS/MET RO works up to 2001.…”

“…In future, combination of GPS RO data and a new area of the GPS reflection may provide a simple measurement tool for global observation of the interaction of ocean-atmosphere-ionosphere (Tyler 1966;Pavelyev et al 1996;Komjathy et al 1999;Beyerle and Hocke 2001). In addition, Igarashi et al (2000Igarashi et al ( , 2001Igarashi et al ( , 2002, Pavelyev et al (2002aPavelyev et al ( , 2002b, and indicated a new possibility to use the amplitude variations in the RO signals to retrieve the vertical electron-density gradients in the lower ionosphere and temperature in the atmosphere. Our aim in this paper is to present a short review of new radio-holographic methods, including their applications to the three-and two-dimensional cases, inhomogeneous medium, to describe their connection with the focused synthetic aperture approach, and to demonstrate that the amplitude data of RO signals can be used (in addition to the phase data) to retrieve the gradients of the electron density in the mesosphere and refractivity in the atmosphere.…”

Analysis of atmospheric and ionospheric structures using the GPS/MET and CHAMP radio occultation database: a methodological review

“…This assumption is usually valid for the upper and middle stratosphere when the ionospheric conditions are quiet. The usual way of obtaining the temperature vertical profile consists of using the Doppler frequency F d found by temporal differentiating the phase path excess U(p) (e.g., Pavelyev et al 2002a):…”

Phase acceleration: a new important parameter in GPS occultation technology

“…For many years, analysis of the Doppler shift variations remained the only practical way to obtain the vertical profiles of the bending angle, impact parameters and refractivity by the use of the trajectory data of satellites. In recent years, new radio-holographic techniques based on the combination of the RO amplitude and phase data have been considered, such as Fresnel diffraction theory (Marouf et al 1986;Mortensen andHoeg 1998), back-propagation (Gorbunov andBengtson 1996;Hinson et al 1997), synthetic aperture method (Lindal et al 1987;Pavelyev 1998;Sokolovskiy 2001), radioholographic-focused synthetic aperture (RHFSA) (Hocke et al 1999;Igarashi et al 2000Igarashi et al , 2001Igarashi et al , 2002Pavelyev et al 2002Pavelyev et al , 2004, canonical transform (Gorbunov and Lauritsen 2002) and the full spectrum inversion (FSI) method . These studies improved the vertical resolution and accuracy in retrieving physical parameters of the atmosphere and broadened the applicability domain of the RO method.…”