Assesment of atmospheric phase screen impact on Geosynchronous SAR

Abstract

The paper evaluates the effects of Atmospheric Phase Screen on focused Geosynchronous SAR data. We derive theoretical models for the resolution, the interferometric de-correlation and the induced clutter in presence of an APS, whose joint time and space power spectrum is modeled as an extension of the Kolmogorov power law. Finally we provide some statistics gathered from a GB RADAR experiment.Postprint (published version

Demonstrative geosynchronous SAR products affected by clutter and APS decorrelation

“…The focused scene is again the convolution between system IRF and APS spectrum but in this case atmosphere decorrelation time and system observation time are of the same order of magnitude, resulting in a slight defocusing and blurring of the focused image [6]. For this reason to obtain high resolution well formed GEOSAR images it is required to estimate and compensate APS as proposed in [10].…”

“…The introduced delay model results in a power spectrum of the APS process where most of the energy is concentrated at the low spatial and temporal frequencies [6]. Note that in GEOSAR demo products generation only the high frequency APS components are introduced since techniques for removing slow varying low resolution APS components (from weather information) can be implemented within GEOSAR processing chain.…”

“…In this time extent several decorrelation sources may affect the quality of the focused GEOSAR data [4]. In particular quickly decorrelating natural targets will spread their energy throughout the focused image as a further background noise [5], whilst, even for targets coherent over long term, the fluctuation of the propagation delay, due to tropospheric and ionospheric turbulences, can introduce defocusing and blurring [6].…”

Advanced Radar Geosynchronous Observation System: ARGOS

“…The APS decorrelation shown in Fig. 4 has been computed according to [11] and by assuming a space-time APS variogram (which is the standard deviation of the differential delay measured in two targets and distance r meters, after t seconds), i.e.,…”

“…Nonetheless, geostationary SAR image quality is impaired by both the atmospheric phase screen (APS) [3], [9]- [11] and the backscatter decorrelation in the one-day revisit. The mitigation of decorrelation demands for long wavelengths, and in fact, typically, L-band is proposed for geosynchronous SAR.…”