Validation of the Calibration Coefficient of the ZY1-02E VNIC Sensor Using Different Calibration Reference

ZY1-02E is a medium-resolution hyperspectral operational satellite equipped with a Visible-Near Infrared Camera (VNIC), an Advanced Hyperspectral Imager (AHSI), and a Thermal Infrared Sensor (IRS). These instruments collectively provide detailed geo-morphological data that enhance environmental and resource monitoring applications. Achieving high-precision radiometric calibration is essential to fully leverage the data from ZY1-02E. This study evaluates the on-orbit radiometric performance of the ZY1-02E VNIC sensor through two calibration methods: vicarious radiometric calibration and cross-calibration. For vicarious calibration, synchronized satellite-ground observation experiments were carried out at the Dunhuang radiometric calibration site (DRCS). The reflectance-based approach was employed to validate the absolute radiometric accuracy of the VNIC. For cross-calibration, data from ZY1-02E VNIC obtained during synchronized overpasses of the DRCS were calibrated against reference sensors including Landsat-8 OLI, Landsat-9 OLI2, and Sentinel-2 MSI. Calibration coefficients were derived, and their accuracy was quantitatively evaluated. The results demonstrate that the vicarious radiometric calibration achieves an average accuracy better than 6% in the visible and near-infrared (NIR) bands, with the calibration from April showing superior performance to that of October. The average relative difference among calibration outcomes derived from various reference sensors is maintained within 2.89%, with Landsat-9 OLI2 exhibiting the closest alignment to the vicarious calibration results, showing an average relative difference of only 1.96%. Overall, the ZY1-02E VNIC sensor displays stable and excellent on-orbit radiometric performance, which is pivotal for supporting quantitative applications in environmental monitoring and resource management.