Abstract
Sentinel-1 (S-1) has an unparalleled mapping capacity. In interferometric wide swath (IW) mode, three subswaths imaged in the novel Terrain Observation by Progressive Scans (TOPS) SAR mode result in a total swath width of 250 km. S-1 has become the European workhorse for large area mapping and interferometric monitoring at medium resolution. The interferometric processing of TOPS data however requires special consideration of the signal properties, resulting from the ScanSAR-type burst imaging and the antenna beam steering in azimuth. The high Doppler rate in azimuth sets very stringent coregistration requirements, making the use of enhanced spectral diversity (ESD) necessary to obtain the required fine azimuth coregistration accuracy. Other unique aspects of processing IW data, such as azimuth spectral filtering, image resampling, and data deramping and reramping, are reviewed, giving a recipe-like description that enables the user community to use S-1 IW mode repeat-pass SAR data. Interferometric results from S-1A are provided, demonstrating the mapping capacity of the S-1 system and its interferometric suitability for geophysical applications. An interferometric evaluation of a coherent interferometric pair over Salar de Uyuni, Bolivia, is provided, where several aspects related to coregistration, deramping, and synchronization are analyzed. Additionally, a spatiotemporal evaluation of the along-track shifts, which are directly related to the orbital/instrument timing error, measured from the SAR data is shown, which justifies the necessity to refine the azimuth shifts with ESD. The spatial evaluation indicates high stability of the azimuth shifts for several slices of a datatake.
Highlights
T HE Sentinel-1 (S-1) mission is based on a constellation of identical C-band synthetic aperture radar (SAR) satellites, which are currently comprised of the A and B units, to provide data continuity to European Space Agency’s (ESA) previous European Remote Sensing (ERS) and ENVISAT SAR missions.The joint operation of both satellites will provide data sets for Copernicus Services [1] for the following areas: monitoring of sea ice zones and the arctic environment, surveillance of the marine environment, monitoring of land surface motion risks, mapping of land surfaces, and mapping in support of humanitarian aid in crisis situations.The S-1A unit was launched in April 2014, reaching its reference orbit on August 7, 2014
We summarize the experience and results obtained with two independent Interferometric SAR (InSAR) processors developed at the DLR, which are the Integrated Wide Area Processor (IWAP) [19] and the experimental TanDEM-X interferometric processor (TAXI) [20]
The first interferometric wide swath (IW) InSAR pair was available in ascending geometry over the Gulf of Genoa, Italy, on August 19, 2014, 12 days after S-1A had reached its final orbit on August 7, 2014
Summary
T HE Sentinel-1 (S-1) mission is based on a constellation of identical C-band synthetic aperture radar (SAR) satellites, which are currently comprised of the A and B units, to provide data continuity to European Space Agency’s (ESA) previous European Remote Sensing (ERS) and ENVISAT SAR missions. Prior to the launch of S-1A, an experimental three-subswath TOPS mode was implemented on RADARSAT-2, operating at the same C-band frequency as S-1, to simulate S-1-like IW mode data products to support the development of processing and exploitation of S-1 IW TOPS data with a particular focus on SAR interferometry [11], [12]. In [18], the description of burst-mode interferometric signal properties is provided, covering, among other issues, azimuth scanning pattern synchronization, spectral shift filtering in the presence of high squint coregistration and subswath alignment, and ScanSAR interferogram formation. This paper focuses on the interferometric processing of S-1 IW mode data acquired over stationary scenes and provides a recipe-like description of the required operations. In the Appendix, we briefly review the S-1 data product description and outline practical information on how to handle the IW SLC data format
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