The Microwave Sounding Unit (MSU) Brightness Temperature (BT) Climate Data Record (CDR) is a long term measurement of the mean temperature from a thick layer of the atmosphere retrieved by the microwave sounder in satellite swath format (level‑1c), and through channel-weighting functions as defined in the MSU BT CDR supporting documentation. The raw counts data from the Earth and blackbody views, which are saved in operational level-b files, are available from the NCEI Comprehensive Large Array-data Stewardship System (CLASS) and act as input to the CDR. Raw counts data are calibrated using the NOAA STAR Integrated Microwave Inter-calibration Approach (IMICA). This approach also accounts for non-linearity and artificial instrumental drifts, and generates the final consistent brightness temperature for the CDR. The final record extends from 1978-2006.