Presented at the 13th Specialist Meeting on Microwave Radiometry and Remote Sensing of the EnvironmentOver the course of the more than four-year mission several enhancements have been developed for the calibration of the zero-baseline radiometers of ESA's SMOS (Soil Moisture Ocean Salinity) mission. Here a particular advancement in adjusting the antenna loss parameters is highlighted. Two methods that enable estimation of the antenna loss are utilized to update the calibration parameters. The impact of the new parameters is evaluated with respect to synthesized antenna temperature which is based on the simulator developed for the Aquarius instrument. The results indicate that the new parameters yield measurements which are significantly closer to the simulated values over the life-time of the mission. This suggests that the new parameters indeed improve the performance of the zero-baseline measurement of SMOS which improves the overall accuracy and stability of the SMOS brightness temperature products.