GPS-based tomographic reconstruction of the ionosphere

Abstract

Modern space navigational system GPS Navstar and its Russian analogue GLONASS allow to measure not only phase, but also group delays of the signals propagating through the ionosphere. Possibility of total electron content absolute measurements removes problem of unknown initial phase always existing for phase measurements in 150/400 MHz band but ground-based ionosphere tomography on GPS basis is impossible for realization. To remove these dificulties we offer to replace angular transmitter movement as it is in the case of radiotomography using TRANSIT system by fast moving of a receiver located on board of low-orbital satellite, thus having saved the condition of frozen ionosphere during measurements. For this purposes it is convenient to use independent compact satellites separated from space station ALFA. It is shown that equal inclinations of GPS orbits and orbital system ALFA provide ideal conditions for 2D-radiotomography application. GPS-based tomographic reconstraction provides the possibility to study the ionosphere above the ISS orbit, which is very interesting from a scientific point of view. During some ISS orbits one can map the global structure of the ionosphere which is very useful also for monitoring and forecasting of natural hazards (earthquakes).