Radiometric stability of the SABER instrument

The SABER instrument on the National Aeronautics and Space Administration Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite continues to provide a long-term record of Earth's stratosphere, mesosphere, and lower thermosphere. The SABER data are being used to examine long-term changes and trends in temperature, water vapor, and carbon dioxide. A tacit, central assumption of these analyses is that the SABER instrument radiometric calibration is not changing with time; that is, the instrument is stable. SABER stratospheric temperatures and those derived from Global Positioning System Radio Occultation measurements are compared to examine SABER's stability. Global Positioning System Radio Occultation measurements are inherently stable due to the accuracy and traceability of the measured phase delay rate to the Systeme Internationale definition of the second. Differences in global annual mean SABER and COSMIC lower stratospheric temperatures show little significant change with time in the 11 years spanning 2007-2017. From this analysis we infer that SABER temperatures are stable to better than 0.1 to 0.2 K per decade.