Infrared(IR) observations from Spinning Enhanced Visible and Infrared Imager(SEVIRI) on board Meteosat Second Generation(MSG)-2 satellite are assimilated into NCEP(National Centers for Environmental Prediction) global data assimilation system(GDAS).The assimilation of current Geostationary Operational Environmental Satellite(GOES) Imager data was also reinvestigated.The Community Radiative Transfer Model(CRTM) was used as observation operator for the simulation of SEVIRI radiance observations.The CRTM was enhanced with several critical components for IR radiance simulation,such as a dynamically-updated land surface emissivity data,as well as fast and accurate gaseous absorption modules.The Global Space-Based Inter-Calibration System(GSICS) calibration corrections were applied to improve the simulation of SEVIRI and GOES Imager radiances.Preliminary results show that inclusions of the SEVIRI radiances at water vapor channels(6.25 and 7.35 μm) and CO₂channel(13.40 μm) in Global Forecast System(GFS) produced significant positive impacts on the six-day forecasts.Assimilation of other five SEVIRI IR window channels in GFS reduces the positive impact.By applying GSICS calibration algorithm to correct SEVIRI and GOES-12 Imager observations biases,the impacts on GFS forecast were improved.Further studies are being carried out to improve the effective assimilation of SEVIRI IR window channels radiances.