On Monday, February 22, 1999, at approximately 1550 GMT, NOAA engineers will change the bias mode used in the GOES-10 Sounder calibration process, to help minimize drift in the bias factors (intercepts) between space looks. Bias Mode 2 will allow the bias to be calculated more frequently, and estimated based on its correlation with the variation in optics temperature. During certain parts of the day when optics temperatures are changing rapidly, this mode provides a better correlation between bias variation and optics temperature, and will ultimately provide for a higher-quality sounding. Peter J. Celone NOAA/NESDIS/Office of Satellite Operations Rm 0151 FB4 301-457-5180 x 167 pcelone@nesdis.noaa.gov