EVALUATION OF SATELLITE AERODYNAMIC AND RADIATION PRESSURE ACCELERATION MODELS USING ACCELEROMETER DATA
Models of non gravitational accelerations, of which satellite aerodynamics and radiation pressure are the most important examples, are critical for many orbit determination and prediction applications. Such models typically consist of three parts, each of which can be implemented at various levels of sophistication, depending on the required accuracy of the application. The first part consists of a model of the environment, such as the density of the atmospheric particles, or the direction and magnitude of the photon flux coming from the Sun and Earth. The second part is a model of the geometry and material properties of the satellite's outer surfaces, while the third part is a representation of the interaction between the particles and the surfaces. In its most simple form, these last two parts combined can be expressed in terms of a constant satellite ballistic coefficient. Traditionally, the implementation of non gravitational models in astrodynamics tools is based on a semi empirical approach, and their assessment is based on an evaluation of tracking data residuals. The accelerometers on the CHAMP, GRACE, GOCE and Swarm satellites, however, measure the sum of the non gravitational accelerations directly. The combination of these observations with non gravitational acceleration models has led to the availability of thermospheric data sets with many scientific applications in the field of aeronomy. In this paper, the experience obtained with the processing of accelerometer data and the use of non gravitational force models for aeronomy applications is demonstrated, and applied in order to provide useful pointers for the implementation of such models in orbit determination and prediction tools at various levels of complexity and accuracy.