Geosynchronous SAR Focusing With Atmospheric Phase Screen Retrieval and Compensation

Abstract

In this paper, a geosynchronous synthetic aperture radar (SAR) (GEOSAR) mission for atmospheric phase screen (APS) retrieval using a long coherent integration of pulses is analyzed. The nearly fixed position of the geosynchronous platforms makes GEOSAR systems suitable for continuous monitoring applications. However, using moderate transmitted powers and antenna sizes, very long integration times up to hours are required. In GEOSAR, the two-way propagation of radar signals can decorrelate significantly due to atmospheric changes during the long data take, resulting in an APS which can cause image defocusing and artifacts. In this paper, the APS effects are analyzed, and an APS correction algorithm from short-term periodic acquisitions (subapertures) of the whole long-term GEOSAR synthetic aperture is described. The results obtained from the APS retrieval algorithm in a simulated GEOSAR acquisition affected by atmospheric decorrelation are presented. Finally, an experimental test of the APS algorithm performance with a long-integration ground-based SAR acquisition is shown

Radar remote sensing from space for surface deformation analysis: present and future opportunities from the new SAR sensor generation

“…A final consideration is devoted to possible use of future SAR systems in geosynchronous or geostationary orbits (Ruiz Rodon et al 2013). In this case, the satellite is placed in a geostationary orbit and the orbit jitter is used to form the synthetic aperture; the spread losses due to the increased satellite-Earth distance are compensated by increasing the integration time.…”

Performance and Requirements of GEO SAR Systems in the Presence of Radio Frequency Interferences

“…Nevertheless, it needs an integration time of hours. Thus, atmosphere distortion is a serious problem in this design [30]. GEO SAR has a longer integration time and a larger coverage compared with a Low Earth Orbit SAR (LEO SAR).…”

Interferometric orbit determination for geostationary satellites

“…The resulting δx value must be added to the initial state and the least-squares algorithm will iterate again by using this new initial state value until a convergence criterion is reached 4) . Once the convergence criterion is achieved, the improved initial state will be provided by the algorithm.…”

“…An accurate image of the scene after SAR processing can be obtained if the range history of every point of the scene is accurately known. This fact necessitates high-precision orbit modeling (with accuracies in the order of magnitude of λ), the use of suitable techniques for atmospheric phase screen compensation [4], and the study and correction of ionospheric effects [5], especially at large wavelengths such as the L band. Such orbital determination requirements are well beyond the usual systems used to manage repositioning of satellites in geostationary orbits.…”