Ionospheric Effects on Spaceborne Synthetic Aperture Radar and a New Capability of Imaging the Ionosphere From Space

Abstract

This article reviews research activities and results in a new field, where ionospheric effects on spaceborne synthetic aperture radar have been investigated and techniques of imaging the ionosphere using the same radar are also explored. The research was originally to minimize ionospheric‐induced distortions and contaminations in Earth remote sensing observations. As a product, the radar‐based high‐resolution ionospheric imaging from a low Earth orbit satellite can also benefit studies of space weather effects on the ionospheric density distribution in essentially all latitude regions, which would provide useful information to studies of coupling of the magnetosphere, ionosphere, and thermosphere.

Measurement of Ionospheric Scintillation Parameters From SAR Images Using Corner Reflectors

“…T HE ionosphere imposes a number of effects on the signals and images collected by space-based L-and P-band synthetic aperture radars (SARs), including Faraday rotation, image shift, defocusing, and amplitude modulation. A recent short review [1] provides a useful collation of much of the contemporary literature.…”

“…Previous studies of the impact of the ionosphere on SAR systems have primarily addressed the effects of Faraday rotation [1] and [2]. However, defocusing and reduction in image contrast due to small-scale ionospheric irregularities has also been recognized.…”

“…A few authors have also explored the inverse problem of how a space-based SAR might be used to image largescale features in the ionosphere and again [1] provides a useful review of the literature. For example, [9] discussed how the ionospheric phase advance and group delay might be measured by interferometric techniques and [10] developed a technique using PALSAR-1 [11] polarimetric data to generate 2-D ionospheric images.…”

Improved TEC retrieval based on spaceborne PolSAR data

“…Recently, the use of low‐frequency spaceborne SAR for measuring ionospheric information, i.e., the total electron content (TEC), has attracted increasing interest [e.g., Meyer et al ., ; Rosen et al ., ; Jehle et al ., ; Meyer , ; Pi et al ., ; Wang et al ., ; Maeda et al ., ]. Combining with the high spatial resolution of spaceborne SAR, this new field has the capability to obtain a kilometer‐scale TEC distribution, which is difficult to be detected by conventionally used data source [ Pi , ]. The spaceborne SAR systems at L‐band or lower frequencies seriously suffer from the ionosphere due to its nature of dispersion.…”

“…By comparing with the phase advances in images of an interferometric SAR (InSAR) pair over the same scene at different time, the difference of TEC between two passes can be exactly derived. However, it is a pity that the absolute TEC values for each pass cannot be obtained by this technique [ Pi , ]. Due to the effects of FR angle, the covariance matrix of PolSAR data is altered.…”