Space-Based Sentinels for Measurement of Infrared Cooling in the Thermosphere for Improved Space Weather Forecasting

Infrared radiative cooling by nitric oxide and carbon dioxide modulates the thermosphere’s density and thermal response to geomagnetic storms. Over the past several years, failed density forecasts have been tied to onset of rapid and significant cooling due to production of nitric oxide and its associated radiative cooling via emission of infrared radiation at 5.3 um. These results have been diagnosed, after the fact, through analyses of infrared cooling made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument now in orbit over 15 years on the NASA TIMED satellite. Radiative cooling rates for nitric oxide and carbon dioxide have been further shown to be directly correlated with composition and exospheric temperature changes during geomagnetic storms. These results strongly suggest that a network of cubesats/smallsats observing the infrared radiative cooling of the thermosphere could serve as space weather sentinels. These sentinels would observe and provide radiative cooling rate data in real time to generate nowcasts of density and aerodynamic drag on space vehicles. Currently, radiative cooling is not directly considered in space weather forecast models. In addition, recent research has shown that different geomagnetic storm types generate substantially different infrared radiative response, and hence, substantially different thermospheric density response. The ability to identify these storms, and to measure and predict the Earth’s nascent response to them, should enable substantial improvement in thermospheric density forecasts.