A Network-Based Enhanced Spectral Diversity Approach for TOPS Time-Series Analysis

• Published in: IEEE transactions on geoscience and remote sensing Vol. 55; no. 2; pp. 777 - 786
• Main Authors: Fattahi, Heresh, Agram, Piyush, Simons, Mark
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Azimuth; Coordinate systems; Coordinates; Coregistration; Digital Elevation Models; Direction; Doppler effect; Electrostatic discharges; Errors; Geometric accuracy; Geometry; Image acquisition; interferometric synthetic aperture radar (InSAR); Radar imaging; Resolution; SAR (radar); Satellite orbits; Satellite tracking; Satellites; spectral diversity; Synthetic aperture radar; terrain observation by progressive scan (TOPS); Time series; Uncertainty; Workflow
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2016.2614925

For multitemporal analysis of synthetic aperture radar (SAR) images acquired with a terrain observation by progressive scan (TOPS) mode, all acquisitions from a given satellite track must be coregistered to a reference coordinate system with accuracies better than 0.001 of a pixel (assuming full SAR resolution) in the azimuth direction. Such a high accuracy can be achieved through geometric coregistration, using precise satellite orbits and a digital elevation model, followed by a refinement step using a time-series analysis of coregistration errors. These errors represent the misregistration between all TOPS acquisitions relative to the reference coordinate system. We develop a workflow to estimate the time series of azimuth misregistration using a network-based enhanced spectral diversity (NESD) approach, in order to reduce the impact of temporal decorrelation on coregistration. Example time series of misregistration inferred for five tracks of Sentinel-1 TOPS acquisitions indicates a maximum relative azimuth misregistration of less than 0.01 of the full azimuth resolution between the TOPS acquisitions in the studied areas. Standard deviation of the estimated misregistration time series for different stacks varies from 1.1e-3 to 2e-3 of the azimuth resolution, equivalent to 1.6-2.8 cm orbital uncertainty in the azimuth direction. These values fall within the 1-sigma orbital uncertainty of the Sentinel-1 orbits and imply that orbital uncertainty is most likely the main source of the constant azimuth misregistration between different TOPS acquisitions. We propagate the uncertainty of individual misregistration estimated with ESD to the misregistration time series estimated with NESD and investigate the different challenges for operationalizing NESD.