We present observations of the energy budget and composition of the mesosphere and lower thermosphere (MLT) over the past 15 years observed by the SABER instrument on the TIMED satellite. Natural variability is evident on timescales ranging from days (e.g., harmonics of the solar rotation period) to decades (e.g., the 11-year solar cycle). Trends in MLT carbon dioxide have been observed in the SABER data record, illustrating the truly “global” nature of global atmospheric change. A reconstruction of the infrared energy budget in the thermosphere extending back 70 years has also been developed. From this reconstruction we further evaluate the magnitude of solar variability from one solar cycle to the next. We have the remarkable result that the total infrared energy radiated by the thermosphere varies by only a small amount from one solar cycle to the next. For solar cycles 19 to 23, solar cycle 23 was in fact the strongest in terms of radiated infrared energy. Lastly, we look to the future and discuss the prospects and priorities for continuing the space-based data record of MLT temperature, composition, and energetics. The SABER-II instrument will be presented and a discussion of a new mission to explore the “heat sink” region of the thermosphere will be given.