Ionospheric Effects on Microwave Signals
The ionosphere is a dispersive medium for space geodetic techniques operating in the microwave band. Thus, signals traveling through this medium are—to the first approximation—affected proportionally to the inverse of the square of their frequencies. This
- PDF / 722,844 Bytes
- 37 Pages / 439.37 x 666.142 pts Page_size
- 94 Downloads / 200 Views
Abstract The ionosphere is a dispersive medium for space geodetic techniques operating in the microwave band. Thus, signals traveling through this medium are— to the first approximation—affected proportionally to the inverse of the square of their frequencies. This effect, on the other hand, can reveal information about the parameters of the ionosphere in terms of Total Electron Content (TEC) of the electron density. This part of the book provides an overview of ionospheric effects on microwave signals. First, the group and phase velocities are defined along with the refractive index in the ionosphere and the ionospheric delay. Then, we focus mainly on the mitigation and elimination of ionospheric delays in the analysis of space M. Mahdi Alizadeh (B) Department for Geodesy and Geoinformation Science, Technical University of Berlin, Strasse des 17. Juni, 135, 10623 Berlin, Germany e-mail: [email protected] D. D. Wijaya Geodesy Research Group, Institute of Technology Bandung, Ganesha 10, Bandung-West Java, Indonesia e-mail: [email protected] T. Hobiger Space-Time Standards Laboratory, Applied Electromagnetic Research, National Institute of Information and Communications Technology, 4-2-1 Nukui-Kitamachi, Koganei, 184-8795 Tokyo, Japan e-mail: [email protected] R. Weber Department of Geodesy and Geoinformation, Vienna University of Technology, Gußhausstraße 27-29, 1040 Vienna, Austria e-mail: [email protected] H. Schuh Department 1 Geodesy and Remote Sensing, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg A 17, 14473 Potsdam, Germany e-mail: [email protected] J. Böhm and H. Schuh (eds.), Atmospheric Effects in Space Geodesy, Springer Atmospheric Sciences, DOI: 10.1007/978-3-642-36932-2_2, © Springer-Verlag Berlin Heidelberg 2013
35
36
M. Mahdi Alizadeh et al.
geodetic observations, specifically for Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI) observations. In particular, we summarize existing models as well as strategies based on observations at two or more frequencies to eliminate first and higher order delays. Finally, we review various space geodetic techniques (including satellite altimetry and radio occultation data) for estimating values and maps of TEC.
1 Group and Phase Velocity The characteristic of an electromagnetic wave propagating in space is defined by its frequency f and wavelength λ. In a dispersive medium, the propagation velocity of an electromagnetic wave is dependent on its frequency. In such a medium the propagation velocities of a sinusoidal wave and a wave group are different. The propagation velocity of a sinusoidal wave with a uniform wavelength is called the phase velocity ν ph , while the propagation velocity of the wave group is referred to as group velocity νgr . Within the vacuum the phase and group velocities are the same, but in the real conditions, this is not the case. Following Wells (1974) the velocity of phase is (1) ν ph = λ f. In general, the carrier waves propagate wi
Data Loading...
