Objectives Lutan-1 (LT-1) satellites are the first scientific research satellite constellation with interferometric synthetic aperture radar (InSAR) measurement of surface deformation as its main features and focusing on long-term natural disaster monitoring and warning in complex areas. It consists of two L-band synthetic aperture radar (SAR） satellites with the same hardware parameters, and has high resolution, high revisit, and full polarization imaging capabilities. The constellation uses the bi-satellites “single-pass in close formation” mode to map terrain, and the bi-satellites “repeat-track” mode to measure surface deformation. Taking the Xieliupo landslide in Zhouqu County, Gansu Province, China as a demonstration example, the ability to monitor large deformation was tested using 4 d and 8 d high revisit observation data.
Methods The interferometric point target analysis (IPTA) method was used to perform InSAR deformation time-series analysis on the Xieliupo landslide. The artificial corner reflector (CR) and global navigation satellite system (GNSS) were installed at the same location of the landslide, and the position of GNSS ground equipment was identified and confirmed by the CR on LT-1 data. The observation results of GNSS were used to verify the accuracy of InSAR results.
Results The annual cumulative maximum deformation of the landslide body exceeds 3.4 m. The accuracy of InSAR deformation time-series obtained from LT-1 satellites reaches 7.5 mm in line of sight. The maximum deformation rates of the tail, middle, and foreside of the landslide exceed 25 mm/d, 11 mm/d, and 2 mm/d, respectively, which indicates the landslide is in the stage from slow sliding to very slow sliding.
Conclusions Through the comprehensive analysis of imaging mode, repeated observation interval, coherence change, baseline control range, and deformation detection ability, it can be found that the comprehensive efficiency of LT-1 satellite has reached the design indicators, and LT-1 satellite has good ability in regularized wide area surface deformation and monitoring. The high-frequency, strict regression, and consistent observation mode of LT-1 will play an important role in geological hazards identifying and monitoring on large-scale.
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