Abstract: To analyze the on-orbit performance realization of the 2-D L-band aperture synthesis microwave radiometer (LASMR) aboard Chinese Ocean Salinity and Soil Moisture Mission (COSM), an in-depth study was conducted on the test results of the payload system, including both the ground verification tests prior to launch and the on-orbit function and performance tests. Prior to launch, ground verification activities-including antenna pattern testing, anechoic chamber point-source imaging, temperature control experiments, and aerial flight tests-were conducted to preliminarily validate the operational principle and core functional effectiveness of the payload system. During the on-orbit testing phase, systematic tests were carried out on the functional and performance metrics of the LASMR, including imaging capability, swath width, sensitivity, and salinity retrieval accuracy. The results show that: the imaging function operates normally; the ground swath width reaches 956km; the sensitivity attains 0.91K; the single-measurement accuracy of seawater salinity hits 0.28psu; and the accuracy is improved to 0.097psu after spatiotemporal averaging processing. The study demonstrates that the ground verification of the synthetic aperture radiometer was comprehensive, and its in-orbit performance is excellent, successfully achieving salinity detection precision surpassing 0.1 psu. This provides critical technological support for dynamic global ocean salinity monitoring.

Key words: Chinese Ocean Salinity and Soil Moisture Mission, 2-D L-band aperture synthesis microwave radiometer, ground verification activities, on-orbit testing phase, performance