TOPS Interferometry With Sentinel-1

The Sentinel-1 SAR mission is designed to provide an independent and operational information capacity to support monitoring environmental conditions based on ERS and ENVISAT data. A new wide swath imaging mode, TOPS, has been proposed. The Sentinel-1 IW modes acquire data of wide swaths using the TOPS imaging technique. It overcomes the problems by the conventional ScanSAR mode by mean of steering the antenna along-track. Howerer, all targets are observed under the same azimuth antenna pattern, the therefore the scalloping effect in drastically reduced and distributed target ambiguities noise ratio (DTAR) and signal-to-noise ratio (SNR) become nearly constant in azimuth.TOPS bursts are much longer than the scanSAR bursts and the acquired data have large Doppler centroid variations within a burst.The coregistation requirements for burst mode data are more demanding than for conventaional stripmap data due to significant Doppler frequency variation of the focused bursts. Special attention is given to the co-registration of the radar images, which poses strict requirements regarding the accuracy. An overall azimuth coregistration accuracy of better than 0.001 of the pixel is required for this configuration in order to achieve that phase error is smaller than three degrees. Then we propose two methods for TOPS images coregistration. The first proposed coregistration approach consists on a geometric prediction of the shifts using precise orbit information and an external DEM. Our proposal to obtain high accuracy is to apply correlation techniques in order to correct residual deviations of the geometric co-registration estimates. These deviations are due to orbital error and shifts induced by geodynamic effects.The orbit information is distributed later one month than original data. That would be unfortunable for real-time data processing. ESD method has an important draw back, Due to the larger sensitivity, the ESD phase might be wrapped. So we propose second methed that we use the ICC method at Swath level to compenside the residual deviations and ensured that the residual coregistration error is smaller than this limit, otherwise a wrapped value will be estimated.ESD method has another draw back in non-stationary scenarios. Interferometric phase jumps observed at the burst edges might be legitimate geophysical signals and ionosphere. One should be careful in distinguishing the source of the displacements. This paper focus this phenomenon and discuss how to avoid the disturb of geophysical signal and ionosphere.The mission of PSInSAR technique is extracting PS point and an effective separation of the various contributions carried out by exploiting the time-space statistical properties of each. The atmospheric signal which is the main error source of InSAR can be isolated from the other components of the residual phase by low-pass filtering in the spatial domain and high-pass filtering in the temporal domain by classical filters. Optionally, after 3D unwrapping, high-pass filtering can be applied to unwrapped data in time followed by a low-pass filter in space in order to remove the remaining spatial correlated errors (atmosphere and orbit errors). This implies that when the deformation rate is large, the spectrum of various contributions will overlap and the classic filter is powerless. So this paper present the methodologies which can automatic choice the smoothing parameter based on a fast robust version of a discretized smoothing spline instead of classic filter to separate the phase components effectively.The Sentinel-1 mission is designed to provide enhanced revisit frequency, coverage, timeliness and reliability for operational services and applications requiring long time series. When all the targets of TOPS image were focused to zero Doppler position referenced the same orbit. The geometry of overlap areas should be same. It was shown that exploiting the burst overlaps it is possible to estimate the precision and accuracy of Persistent Scatterer.