Practical considerations for achieving SI traceability in microwave remote sensing

Microwave brightness temperature (T_b) observations by satellite sounders represent some of the most important input data for numerical weather prediction (NWP) models as well as providing vital records for climate trend detection. Each flight instrument, even if built to nominally identical specifications, has a unique calibration, typically based on the implicit assumption that the on-board black body target is well understood and characterized, but even more importantly that the transfer function between the T_b received at the antenna and the thermometry embedded in the target is well determined.