Space-Based Sentinels for Measurement of Infrared Cooling in the Thermosphere for space Weather Nowcasting and Forecasting

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 NO and its associated radiative cooling via emission of infrared radiation at 5.3 mu m. 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 instrument now in orbit over 16 years on the National Aeronautics and Space Administration Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite. Radiative cooling rates for NO and CO2 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. Plain Language Summary: This paper describes a new class of observations that could dramatically improve the forecasts of conditions in space during space weather events. A network of orbiting sensors would detect the infrared heat radiation from Earth's atmosphere that is generated when energy from the Sun carried by particles in the solar wind interacts with Earth's high atmosphere (above 100 km high). These sensors would serve as an early warming system, relaying their observations to ground stations. These observations would then be fed into forecast models for space weather, just as regular weather satellites track storms near Earth's surface. The new observations would improve the ability to track space objects such as the International Space Station, all orbiting satellites, and orbital debris during the disturbed space weather conditions caused by storms from the Sun.