Understanding and Forecasting the Sun's Impact on the Battlespace Environment

Abstract : The battlespace environment extends far above the surface of the Earth. Of special importance are the outer layers of the Earth's atmosphere, from altitudes 100 to 1000 km, where there is sufficient mass to impede the motion of Earth-orbiting spacecraft, and where layers of charged particles control the propagation of radio waves. Changes in atmospheric "drag" alter the orbits of the thousands of space objects in low Earth orbit (LEO) that are tracked by the U.S. Space Command. The ionosphere transmits, reflects, retards, and refracts kHz to MHz radio wave frequencies. As a result, fluctuations in the neutral and ionized environment can negatively impact Naval operations by disrupting communications and navigation and by degrading radar accuracy, targeting precision, and orbit prediction. The Sun is the primary source of variations in the neutral and ionized upper atmosphere. A suite of new solar and atmospheric data bases that extend over the Sun's 11-year activity cycle are now refining our understanding of the intricately interconnected Sun-Earth system, thereby improving the ability to predict this region's impact on DoD systems. The new data bases include solar imagery from NRL instruments aboard the Solar Heliospheric Observatory (SOHO), daily thermospheric mass density derived from spacecraft drag via a new NRL algorithm, and total electron content obtained from analyses of GPS timing by the Center for Orbit Determination in Europe (CODE).