Precise Solar Radiation Pressure Modeling for GRACE with Atmospheric Effects

The primary objective of the GRACE (Gravity Recovery and Climate Experiment) mission is to characterize the mean and time variable components of Earth's gravity field. The two GRACE spacecraft provide high accuracy accelerometer data which is useful for a variety of other applications including thermosphere density and wind modeling and the study of variations in Earth's neutral density. Solar Radiation Pressure (SRP) modeling is important to these applications. The level of accuracy of the GRACE accelerometers and the large amount of data available from over eight years of measurement provides an opportunity to evaluate SRP modeling methods. The application of a detailed SRP modeling method developed by Professor David Vokrouhlicky of Charles University in Prague has led to very good correlation of modeling results with accelerometer data. The SRP modeling tool currently includes the effects of atmospheric refraction, atmospheric absorption, and Earth oblateness. The attached figure illustrates the influence of including atmospheric effects on the behavior of modeling results and level of correlation with accelerometer data. Sensitivity analyses more thoroughly illustrate the influences of including these effects and of varying atmosphere conditions on the behavior and quality of SRP modeling results.