Optimized Selection of Pseudo-Invariant Calibration Sites for Radiometric Cross-Calibration of Spaceborne Sar Sensors

Radiometric cross-calibration achieves the calibration of uncalibrated satellites by employing calibrated satellites to illuminate the same ground targets. The stability of these ground targets is essential for the effectiveness of radiometric cross-calibration. However, there has been limited research conducted on identifying stable ground targets specifically for SAR radiometric cross-calibration. To address this issue, an optimized selection method for pseudo-invariant calibration sites (PICS) was introduced in this paper. This method began with the acquisition of distributed target masks, followed by the extraction of stable distributed targets based on these masks. Sentinel-1 time series images were utilized to select candidate distributed targets, with a specific focus on those with a temporal root mean square error of less than 0.5 dB and a sigma zero value exceeding -16 dB for the purpose of extracting PICS. These sites could accommodate a rise in the frequency and accuracy of SAR radiometric cross-calibration.