First evaluation of the coherence of LuTan-1 bistatic InSAR system

The LuTan-1 (LT-1) mission, consisting of two nearly identical synthetic aperture radar (SAR) satellites, LT-1A and LT-1B, conducted unprecedented L-band bistatic data acquisition from June to December 2022, with the objective of generating high-precision digital elevation models (DEMs) and supporting applications in geology, surveying and mapping, and forest-related studies. Therefore, a systematic evaluation of coherence is necessary, as it facilitates a comprehensive understanding of system performance and data quality, thereby supporting the above applications more effectively. This study first analyzes several error sources that can cause LT-1 coherence loss and provides corresponding data processing workflows, calibration procedures, and compensation strategies. Specifically, the evaluation and analysis include the impacts of co-registration errors, baseline decorrelation, spectral shift, radio frequency interference, ambiguity, limited signal-to-noise ratio, and quantization errors. Subsequently, we focus on decorrelation caused by volume scattering and conduct a sensitivity and application analysis of volume decorrelation with respect to forest and building height, as well as penetration depth in desert and snow-/ice-covered areas. This analysis offers a valuable reference for its application in corresponding specific scenarios. Finally, we present the spatial distribution of coherence derived from all LT-1 bistatic InSAR acquisitions over China, demonstrating the excellent interferometric capability of the LT-1 mission and providing the scientific community with a quality overview of this unique dataset.