The JPSS ATMS has been compared with these reference radiometers by collocation, direct measurement comparison, RTM simulation, and cross-calibration. A line-by-line model has been employed to assess the difference in bandwidth, spectral response function and side-band imbalance. Since some sounding channels sees moderate surface emitted radiance, the cross-calibration is implemented over both oceanic and land scenes. The over-land comparison is done over the worldwide forests that are near blackbody targets and insensitive to incidence angle. The comparison covers a range of aspects including the average TB difference, cross-track characteristics, and inter-sensor biases dependence on TB. To conclude, JPSS ATMS brightness temperature shows consistency through comparison against the other microwave radiometers. Its calibration and performance are stable and consistent in the past almost two years since its launch.