South China Sea Annual Meeting 2023 (SCSAM)

Ocean salinity, as one of the major ocean dynamic factors, plays a significant role in ocean circulation, climate change and global water cycle. Till now, the salinity is the only missing element in the observation history of China's ocean satellites. The Chinese Ocean Salinity Mission (hereinafter referred to as COSM), which is China's first satellite for sea surface salinity observation, belongs to the "13th Five-Year Plan" for the Ocean Dynamic Environment serial satellites. The COSM will obtain the global large-scale and time-sensitive ocean salinity information using two novel payloads called the Interferometric Microwave Radiometer (IMR) and the Microwave Imager Combined Active and Passive (MICAP). The launch of the COSM will improve the remote sensing capability of China's ocean dynamic environmental elements, serving the national major strategic needs of " Maritime Power ". The COSM was approved in November 2020 and planned to be launched around 2024 or 2025, and now is heading into the payloads manufacture stage. At present, the flight calibration experiment is in progress, carrying two airborne instruments. The airborne instruments, which are the scale model of spaceborne payloads, are used to verify the synthetic aperture payloads performance, the data processing technique and the key error correction methods. Since the experiment aims to obtain salinity quantitatively, an end-to-end pre-simulation is performed to the airborne-IMR and MICAP. Based on the flight attitude and airborne instruments configuration, the pre-simulation calculates the interferometric radiometer’s measurement, and key parameters such as the TB radiometric resolution, the spatial resolution and the incidence angle. Then, two parameter retrieval algorithms, named the stepped retrieval and the combined retrieval, are performed to produce the sea surface salinity, temperature and wind speed. Finally, the accuracy assessment of the flight experiment is presented. Our pre-simulation works help to quantify the whole experiment, and the methods used in the simulation will be verified in the following airborne data processing.