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

Abstract:

Infrared radiative cooling by nitric oxide (NO) and carbon dioxide (CO₂) modulates the thermosphere’s density and thermal response to geomagnetic storms. Satellite tracking and collision avoidance planning require accurate density forecasts during these events. Over the past several years, failed density forecasts have been tied to the 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 measurements of infrared cooling made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument now in orbit over 16 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 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 operational 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 response to them, should enable substantial improvement in thermospheric density forecasts. This talk will review the scientific basis for using infrared cooling rates to facilitate the prediction of density variations during geomagnetic storm events. We will also review design considerations for small infrared sensors that could provide the real-time measurements of infrared cooling for nowcasts of thermospheric density during disturbed conditions