An On-orbit parameter adjustment approach for DQ-1 Directional Polarimetric Camera based on the cloud data of MODIS/AUQA

The Directional Polarimetric Camera (DPC) has been successfully launched on April 16, 2022, onboard the Atmospheric Environment Monitoring Satellite (DQ-1). The DPC is an ultra-wide-angle satellite-borne sensor with a swath width of 1850 km, enabling global coverage within two days. The DPC offers three operational modes: land, ocean, and custom. Given the lack of on-board calibrator, the initial state needs to be calibrated through natural features to determine the instrumental parameters suitable for cloud measurements. Meanwhile, the data products of MODIS are used as references. The experimental results show that: 1) the initial cloud optical thickness (COT) histogram trend is consistent, with significant differences in high value areas. The preset parameters limit the calculation of thick clouds with COT greater than 50, presenting a saturation situation; 2) Selecting the deep convective cloud (DCC) targets, quantitative analysis is conducted between MODIS band 1 L1B data and DPC data. The reflectance at the top of the atmosphere (TOA) of DPC approaches saturation at 0.85; 3) the custom mode is selected, the integration time is reduced by 25 %, the instructions are injected from the ground station. The DPC high reflectivity range is linearly consistent with MODIS, the deviation is <2 %, and the distribution of cloud optical thickness products is in good agreement. The on-orbit parameter adjustment method based on high reflectivity clouds has achieved the expected goals. Customized operational parameters suitable for cloud inversion have been established, providing valuable reference and technical means for instrument operational parameter adjustment and long-term series monitoring calibration.