This website has been inactive since the 2022 Beacon Satellite symposium held in Boston, MA. Following Sputnik in 1958 Electromagnetic Wave (EM) scintillation at frequencies above HF has been dominated by artificial satellite diagnostics, typically narrow band or pulse-compressed signals. Frequency de correlation across signal bandwidths is negligible and coherence scales are within the par axial (narrow range of contributing propagation angles) limits of the statistical theory of scintillation. Formally, the theory is encapsulated in a hierarchy of differential equations for signal moments. However, as a practical matter, multiple phase screen (MPS) simulations provide an alternative framework for evaluating scintillation effects in communication, surveillance (radar), and navigation, positioning, and timing (NPT) applications. Additionally, these results are supported by tractable theoretical calculations that connect the principal scintillation measures, namely the intensity scintillation index, the phase scintillation index, and the rate of change of total electron content. Finally, the entire theory is supported by a small set of parameters that characterize the underlying ionospheric structure, together with the Fresnel scale. Within the limits of the par-axial approximation, propagation distance and frequency are scaled variables. For diagnostic applications the defining structure parameters can be estimated efficiently with a maximum-likelihood-based on irregularity parameter estimation (IPE) procedures.
The acquisition and processing of diagnostic scintillation data has evolved considerably. Early satellite observations relied on NORAD orbital elements for orbital calculations. With the advent of the global positioning system (GPS), navigation and positioning generated more refined and accessible orbital elements, which have been upgraded again to accommodate the global navigation satellite (GNSS) constellations.
The publication of The Theory of Scintillation with Applications in Remote Sensing included MatLab utilities to reproduce the examples in the book, which are part of this website. It is our intent to update the analysis and incorporate new theoretical results. The update is in two parts. The first addresses our attempt to extend what we call the forward propagation equation (FPE) to HF. At HF strongly refracted signals significantly exceed the par-axial limit. We had proceeded with the assumption that using a full wave propagator in the MPS theory would extend the range of applicability. We found that the the results are biased from trajectories predicted by ray theory.
The first part of the update is an evaluation of the limitation and its ramifications, particularly the interpretation of combined scalar wave function solutions interpreted as vector fields. At the present time this is an open issue. The second part of the update is to introduce and demonstrate new diagnostic procedures, which are proving to be particularly relevant to extreme scintillation observed during the current solar cycle activity peak. Finally, some improved and new diagnostic tools have been developed.
