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As a typical propagation error, tropospheric delay has been fully considered during synthetic aperture radar (SAR) interferometry and differential interferometry, while the influence on the SAR imaging process is just concerned in advanced configurations, e.g., staring mode, high-resolution, geosynchronous/geostationary (GEO) SAR. In this article, a comprehensive model of turbulent tropospheric delay (TTD), involving atmospheric sciences and fluid mechanics, is introduced, and the influence of which on high-resolution SAR is analyzed. In order to compensate for the influence of TTD in advanced SAR missions, the autofocus method used in motion error compensation is extended, and a 2-D phase error estimation and compensation algorithm is proposed. Subsequently, the simulation experiments of both dot-matrix targets and TerraSAR-X data are performed to validate the effectiveness of the proposed algorithm. Conclusions and prospects are reached in the end.

In this paper, a novel 3-D imaging method of aerospace targets based on linear array radar is proposed. The traditional ISAR imaging can only show the scattering centers’ projection on the imaging plane, which is hard to be used for target recognition. To overcome this shortcoming, this paper proposes realizing 3-D imaging by a linear array. The key parameters of linear array radar are obtained by analyzing the relationship between of the azimuth ambiguity and the resolution. In the far-field condition, the resolutions of the target image in three dimensions including range, azimuth and height are obtained by using the backward projection algorithm. Experiment based on simulated data shows that the method can achieve accurate 3-D imaging of space objects and have good performance.

Geosynchronous synthetic aperture radar (GEO SAR) can provide daily repeat-pass and high coherent image pairs for interferometry. On the area mapped with thousands of kilometers width, GEO InSAR has some overwhelming advantages in disaster management, tectonic mapping and modeling, vegetation and soil moisture mapping. This paper provides an overview of system requirements for three potential bands (L/S/C) of GEO SAR interferometry applications, including orbit determination accuracy, orbit control accuracy, radar ranging accuracy and noise-equivalent backscattering coefficient. Under some appropriate GEO InSAR configurations and parameters, performance predictions of deformation measurement accuracy are given. Results show that lower band GEO InSAR has some lower requirements on satellite orbit measurement, control and maintain accuracy and a higher requirement on radar noise sensitivity instead. It is expected that the deformation measurement accuracy of 2~6 millimeters in local area and 1~3 centimeters in wide area will be available for the three potential bands of GEO InSAR.

An improved interferometric synthetic aperture radar (InSAR) performance evaluation method based on prominent scatterers (PS) is proposed to precisely assess the accuracies of the absolute/relative interferometric phase and the absolute/relative height. The critical technical defect of the conventional PS-based method is analysed, where overvalued performance indexes are caused by higher coherence on the PS than on the ordinary ground scene. Virtual prominent scatterers (VPS) around the actual PS are introduced and treated as statistical samples when the indexes are computed. The pixel location of the VPS is estimated indirectly by utilizing the high signal to clutter ratio of the VPS and the accurate relative location between the PS and the VPS. A spaceborne InSAR signal simulation experiment is carried out to validate the new VPS-based method. The developed method can support performance analysis, error isolation and troubleshooting in InSAR systems.

Amplitude and phase statistics of SAR complex interferogram are significant in the study of interferometry and polarimetry. To reduce statistical variations, multi-look processing is adopted by averaging spatially the complex interferogram. In this study, we derive and validate three kinds of probability density functions (PDFs) of multi-look interferogram for different surface feature scenes. For simple homogeneous areas with the gamma distribution intensity, a concise product-form interferometry phase PDF is derived, which is equivalent to a conventional Gauss hypergeometric PDF. For complicated areas with the K and G0 distributions intensity, two new interferometry amplitude PDFs named as Gamma-K and Gamma-G are proposed, and their phase PDFs are approximately preserved. Finally three typical areas including grass, mountain, and city are picked out from a pair of RADARSAT-2 SAR images and studied. Experimental results indicate good agreement between the computed histograms and the theoretical distributions. The results obtained can be applied to the feature classification of polarisation SAR data and the estimation of decorrelation effect of interferometric SAR. Science Journal, Vol. 64, No. 6, November 2014, pp.564-570, DOI:http://dx.doi.org/10.14429/dsj.64.4747

Standard synthetic aperture radar SAR processors use analytically derived transfer functions that rely on the assumption of hyperbolic range histories of monostatic SARs with straight flight paths. The range histories for bistatic SARs are no longer hyperbolic and simple analytic transforms do not exist. In this article, a bistatic subsection hyperbolic range history BS-HRH model is proposed and based on it; a generic processing scheme for bistatic SAR imaging is given with which simple analytic transforms for standard monostatic SARs can still be applied. One-dimensional and two-dimensional signal-level simulations are done using the orbit parameters of Envisat and a classic pendulum-like bistatic configuration under different baselines. It is found that the proposed BS-HRH algorithm performs well for spaceborne bistatic SARs even with extreme bistatic configurations and/or very high azimuth resolution. Compared with the existing analytical ‘method of series reversion MSR’ and the numerical ‘NuSAR’ algorithm, easy implementation, high efficiency and accuracy, and mathematical simplicity are among the advantages of the proposed algorithm. The approach of BS-HRH has the potential to solve the general HRH-deviation problem for other new SARs with more complex imaging geometry.

Recently, a synthetic aperture radar (SAR) tomograhic focusing method based on compressive sensing was proposed. This focusing method can reduce the required number of measurements and achieve satisfying elevation resolving ability. First, we briefly review this novel focusing method and prove the applicability of compressed sensing (CS) for SAR tomography theoretically using the latest improvement of CS. Then, we apply this focusing method to the 3-D reconstruction of Angel Stadium with Envisat-ASAR data. Both the theoretical analysis and satisfying results of real data processing confirmed the applicability of this SAR tomograhic focusing method.