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Sentinel-1's continuous observation program over all major plate boundary regions makes it well suited for earthquake studies. However, decorrelation due to large displacement gradients and limited azimuth resolution of the Terrain Observation by Progressive Scan (TOPS) data challenge acquiring measurements in the near field of many earthquake ruptures and prevent measurements of displacements in the along-track direction. Here we propose to fully exploit the coherent and incoherent information of TOPS data by using standard interferometric synthetic aperture radar (InSAR), split-bandwidth interferometry in range and azimuth, swath/burst-overlap interferometry, and amplitude cross correlation to map displacements in both the line-of-sight and the along-track directions. Application to the 2016 Kumamoto earthquake sequence reveals the coseismic displacements from the far field to the near field. By adding near-field constraints, the derived slip model reveals more shallow slip than obtained when only using far-field data from InSAR, highlighting the importance of exploiting all coherent and incoherent information in TOPS data.

Zero Doppler centroid imaging is of great significance in synthetic aperture radar interferometry (InSAR). Because the moon's orbit is elliptical and its orientation cannot be changed artificially, the zero Doppler centroid of lunar-based synthetic aperture radar (LB-SAR) is not steerable and will vary with lunar rotation and SAR system's position on lunar surface. Therefore, the distribution of zero Doppler centroid of LB-SAR will provide an important reference for observation model design of LB-SAR/InSAR. In this letter, we propose a calculation method of zero Doppler centroid by using the Jet Propulsion Laboratory (JPL)/NASA development ephemeris 430 (DE430), investigate the spatio-temporal distribution of the zero-Doppler line (ZDL). The results show that 1) the position of zero Doppler centroid deviates from the central meridian of a sublunar point from 0° to 45° within a sidereal month, 2) the maximum longitude difference of ZDLs corresponding to different SAR system's position on lunar surface is about 60 km, and 3) the greatest effect of topography on ZDL estimation is about 1.1 km. The proposed calculation method of ZDL and results analysis are of instructive significance to the site selection and attitude control of lunar-based radar in the design of LB-SAR/InSAR. [ABSTRACT FROM AUTHOR]

With the development of the Moon exploration, the concept of deploying sensors of synthetic aperture radar based on the Moon (Moon-based SAR) to fully and constantly observe the Earth is gaining increased attention. The Moon-based SAR has the advantages of long-term, large-scale and continuous observation, and it may provide a new way for macro-scale solid Earth monitoring. Here, the system parameters theoretically are analyzed and simulated considering at the requirements of large-scale Earth observation. In addition, the actual relative motion parameters of the Earth-Moon system and the performance of the Moon-based SAR imaging are taken into account. The results show that the Moon-based SAR has the potential of ultra-wide observation applications. It can form an imaging swath of thousands of kilometers by using multi-beam SAR with good imaging performance. [ABSTRACT FROM AUTHOR]

Over exploitation of groundwater in Changzhou city, China can cause land deformation, which in turn proves detrimental to the urban infrastructure. In this study, multi-band synthetic aperture radar (SAR) data sets (C-band Envisat ASAR, L-band ALOS PALSAR, and X-band COSMO-SkyMed) acquired from 2006 to 2012 were analysed using the synthetic aperture radar (SAR) interferometry (InSAR) time-series method to investigate the relationship between spatial–temporal distribution of land deformation and groundwater exploitation. Annual deformation rate inferred from multi-band interferograms ranges from −58 to 24 mm year−1. Levelling-survey data were used to validate the multi-band InSAR measurements. The results showed that these two types of measurements were generally in agreement. Correlating groundwater-table and multi-band InSAR measurements at six groundwater-well stations showed that with the rise of the water table, the land rebounded. But in some areas with larger subsidence, continual subsidence was observed even though the water table rose after the prohibition of groundwater exploitation. This may have been caused by the hysteresis effect due to the consolidation of strata (especially for the creep deformation). Our study provides scientific evidence on the management of groundwater extraction and the assessment of land-subsidence hazards. [ABSTRACT FROM PUBLISHER]