As was indicated in the mentioned paper, the ionospheric stripes, in general, aligned well with the orientation of the projected ambient geomagnetic field vector. However, it is shown in our study that the calculated striping heading is not only dependent upon the orientation of the projected ambient geomagnetic field vector, namely, the geomagnetic heading but also the geomagnetic inclination, the system incident, and squint angle. It also confirms that the changing direction of the visible stripes in the mentioned Phased Array-type L-band Synthetic Aperture Radar (PALSAR) data is mainly due to the variation of the geomagnetic inclination, while the geomagnetic heading is nearly constant along the orbit. Therefore, the denotation and presentation in that research that the projected geomagnetic field vector elongates in the direction of the stripe orientation might not be feasible.

Spaceborne multistatic synthetic aperture radar (SAR) tomography (SMS-TomoSAR) systems take full advantage of the flexible configuration of multistatic SAR in the space, time, phase, and frequency dimensions, and simultaneously achieve high-precision height resolution and low-deformation measurement of three-dimensional ground scenes. SMS-TomoSAR currently poses a series of key issues to solve, such as baseline optimization, spatial transmission error estimation and compensation, and the choice of imaging algorithm, which directly affects the performance of height-dimensional imaging and surface deformation measurement. This paper explores the impact of baseline distribution on height-dimensional imaging performance for the baseline optimization issue, and proposes a feasible baseline optimization method. Firstly, the multi-base multi-pass baselines of an SMS-TomoSAR system are considered equivalent to a group of multi-pass baselines from monostatic SAR. Secondly, we establish the equivalent baselines as a symmetric-geometric model to characterize the non-uniform characteristic of baseline distribution. Through experimental simulation and model analysis, an approximately uniform baseline distribution is shown to have better SMS-TomoSAR imaging performance in the height direction. Further, a baseline design method under uniform-perturbation sampling with Gaussian distribution error is proposed. Finally, the imaging performance of different levels of perturbation is compared, and the maximum baseline perturbation allowed by the system is given.

The future L‐band geosynchronous synthetic aperture radar (GEO SAR) system will be inevitably affected by ionospheric scintillation. Due to the lack of the real system, it is necessary to achieve the scintillation‐affected GEO SAR raw data for the research of influential mechanism and correction strategies. A method for the generation of scintillation‐affected GEO SAR raw data is proposed that utilises the reverse backprojection (ReBP) to efficiently and accurately modulate the scintillation transfer function on GEO SAR signals. A simulation experiment for a real SAR scene from one of the ALOS‐PALSAR observation is operated in case of the current inclined L‐band GEO SAR system configuration. The simulation takes less time by using the ReBP, compared with the existent method, and shows the speckle‐like phase error similar to the injected scintillation phase error, which validates the nice efficiency and accuracy of the proposed methodology.

Spaceborne synthetic aperture radar (SAR) polarimetric application, operating at P‐band, is significantly influenced by ionospheric Faraday rotation (FR). Various researches have been published to evaluate the FR effect on polarimetric scattering matrix, nevertheless all of which are based on the narrow‐band hypothesis and ignore the polarimetric dispersion (PD) effect caused by FR for its high disturbance within the bandwidth. The existent model is no longer well applicable to the future P‐band ultra‐wideband system with benefits of the high‐resolution detection of the subsurface or obscured targets. A novel analytical model of PD based on the frequency‐domain range pulse compression is proposed and analysed in this Letter, and the simulation results indicate the spaceborne P‐band ultra‐wideband SAR system is seriously influenced by the PD effect.

Distributed radar array brings several new forthcoming advantages in aerospace target detection and imaging. The two-dimensional distributed array avoids the imperfect motion compensation in coherent processing along slow time and can achieve single snapshot 3D imaging. Some difficulties exist in the 3D imaging processing. The first one is that the distributed array may be only in small amount. This means that the sampling does not meet the Nyquist sample theorem. The second one refers to echoes of objects in the same beam that will be mixed together, which makes sparse optimization dictionary too long for it to bring the huge computation burden in the imaging process. In this paper, we propose an innovative method on 3D imaging of the aerospace targets in the wide airspace with sparse radar array. Firstly, the case of multiple targets is not suitable to be processed uniformly in the imaging process. A 3D Hough transform is proposed based on the range profiles plane difference, which can detect and separate the echoes of different targets. Secondly, in the subsequent imaging process, considering the non-uniform sparse sampling of the distributed array in space, the migration through range cell (MTRC)-tolerated imaging method is proposed to process the signal of the two-dimensional sparse array. The uniformized method combining compressed sensing (CS) imaging in the azimuth direction and matched filtering in the range direction can realize the 3D imaging effectively. Before imaging in the azimuth direction, interpolation in the range direction is carried out. The main contributions of the proposed method are: (1) echo separation based on 3D transform avoids the huge amount of computation of direct sparse optimization imaging of three-dimensional data, and ensures the realizability of the algorithm; and (2) uniformized sparse solving imaging is proposed, which can remove the difficulty cause by MTRC. Simulation experiments verified the effectiveness and feasibility of the proposed method.