The Cross-track Infrared and Microwave Sounding Suite (CrIMSS), consisting of the Cross-track Infrared Sounder (CrIS) and the first space-based, Nyquist-sampled cross-track microwave sounder, the Advanced Technology Microwave Sounder (ATMS), will provide atmospheric vertical profile information needed to improve numerical weather and climate modeling. Recently a near real-time bias monitoring system for the Advanced Microwave Sounder Unit A (AMSU-A) has developed in Center for Satellite Applications and Research (STAR). We simulate the brightness temperatures at 15 channels over oceans corresponding to each AMSU-A beam position and compare the simulated results with the measurements. The radiative transfer modeling used in this study is the JCSDA Community Radiative Transfer Model (CRTM). CRTM simulation is performed under clear atmospheric conditions over ocean using sea surface temperature (SST), wind vector, and temperature/moisture profiles obtained from the National Centers for Environmental Prediction Global Data Assimilation System (GDAS). Key features for this polar orbiting satellite bias monitoring system include global bias distribution, angular dependence distribution and time series monitoring. Similar bias monitoring system will be developed for the ATMS sensor and its heritage sensor the AMSU-A will be used as proxy data before the NPOESS Preparatory Project (NPP) launch.