In-Orbit Geometric Calibration for Long-Linear-Array and Wide-Swath Whisk-Broom TIS of SDGSAT-1

Because of the imaging mechanism complexity of long-linear-array and wide-swath whisk-broom thermal infrared spectrometer (TIS) of the first Sustainable Development Goals Satellite (SDGSAT-1), how to achieve a high geometric positioning accuracy (GPA) becomes the core factor in subsequent geometric quantitative applications. Here, in this article, a three-step in-orbit geometric calibration (GC) strategy comprising the estimations of exterior orientation parameters (EOPs), interior orientation parameters (IOPs), and scanning compensation parameters (SCPs) is proposed to correct the geo-location displacements for whisk-broom TIS. First, in accordance with the optical-mechanical structure and pinhole imaging theory, we establish the rigorous geometric positioning model (RGPM) of TIS and analyze the error resources term-by-term along the error propagation link elaborately. Second, the corresponding rigorous geometric calibration model (RGCM) is constructed in detail based on the 2-D look-angle model and the generalized bias correction matrix. Especially for eliminating the systematic nonlinear errors in the scanning direction, a fifth-degree polynomial is put forward to be employed to fit and compensate for the angular measurement errors of the scanning mirror. Finally, a three-step estimation method is presented to estimate the calibration parameters with ground control points (GCPs). Experimental results based on the spatial references of Landsat 8 panchromatic images and version 2 of advanced spaceborne thermal emission and reflection radiometer (ASTER) global digital elevation model (GDEM2) show that the GPA of the proposed method in along-track and cross-track directions can be better than 1.0 pixels for all three bands, which makes a great sense for associated geometric measurements.