Objectives Lutan-1 (LT-1) satellite is the first synthetic aperture radar (SAR) constellation in China with interferometric applications as its core mission. The constellation consists of two A and B satellites equipped with L-band SAR payloads, with all-day, all-weather, multi-polarization imaging capability, which can be applied to geology, land, earthquake, disaster reduction, mapping and forestry, etc. The A and B satellites are operated in formation configuration, and the fly-around mode is suitable for terrain interferometry, while the follow-fly mode is suitable for deformation interferometry. The fly-around mode is suitable for terrain interferometry; the follow-fly mode is suitable for deformation interferometry. Taking Datong City, Shanxi Province, as the study area, we verify and analyze the topographic measurement accuracy and surface deformation measurement accuracy of LT-1 constellation by combining the data of the two different formation modes of the constellation. We aim to provide an important reference for the operational application of, LT-1 constellation.

Methods In the verification of LT-1 topographic survey accuracy, we first produced digital elevation model (DEM) in the study area using LT-1 data, then used ICESat-2 elevation control points as reference data and Copernicus DEM products as control data, and combined the multiple error evaluation indexes and optical remote sensing imagery we established to compare the DEM quality of LT-1 and Copernicus. In the verification of LT-1 deformation interferometry accuracy, we adopt the temporary coherent point (TCP)-InSAR technique to invert the deformation information of Sentinel-1A images and LT-1 images covering the same time period in the study area, and then compare and evaluate the internal and external conformal accuracies, respectively.

Results The accuracy of LT-1 DEM produced by LT-1 data in the fly-around mode is similar to that of Copernicus, and some evaluation indexes are even better than those of Copernicus DEM. Also, LT-1 DEM have higher spatial resolution, which can show more detailed landscape and terrain features. Meanwhile, LT-1 DEM has higher spatial resolution and can show more detailed geomorphological features. In addition, LT-1 DEM can be further optimized. The deformation field inverted by LT-1 data in the fly-by mode is similar to that of Sentinel-1A in terms of spatial distribution and value, and the correlation coefficient between LT-1 and Sentinel-1A is as high as 0.91. Moreover, LT-1 data are better than Sentinel-1A in terms of image coherence, the number of monitoring points, and the accuracy of deformation measurement.

Conclusions We have verified and analyzed the accuracy of LT-1 data for terrain interferometry and surface deformation interferometry in different formation operation modes, and the results show that LT-1 satellites have great advantages in spatial and temporal resolution and measurement accuracy when used in interferometry missions, and the potential of LT-1 constellation for applications in other geoscience fields is also worth exploring further.