The VIIRS onboard the NPP spacecraft provides continuous operational observations with daily global coverage at a moderate resolution. It is designed with 22 channels which supersedes the traditional AVHRR on NOAA satellites, and extends the MODIS time series for the window channels. In addition, the day night band will allow low light observations at night, extending the capabilities of the OLS on DMSP satellites. This presentation will review the recent progress made in the calibration/validation of VIIRS SDR, with emphasis on postlaunch performance and evaluation of the VIIRS instrument, involving both onboard and vicarious methods. In particular, the extended Simultaneous Nadir Observations (SNO-x) will be discussed. The SNO-x occurs between the NPP and Aqua spacecrafts at a range of latitudes, including the tropics, which creates a great opportunity for intersatellite cal/val for the SDRs as well as EDRs. Preliminary results from the comparisons will be presented. Calibration is critical for ensuring the quality of VIIRS SDRs, which are fundamental to all EDR products.