Using the Attitude Response of Aerostable Spacecraft to Determine Thermospheric Wind

Thermospheric wind can be measured by observing the attitude motion of aerostable spacecraft when allowed to freely react to the aerodynamic torques. Estimates of the spacecraft aerodynamic properties, of the other disturbance torques and of the atmospheric density are required to determine the wind magnitude and direction. Aerostable spacecraft behave as un-damped oscillators with their natural frequency depending on the dynamic pressure and their aerodynamic stiffness. The achievable spatial resolution is proportional to the natural frequency and smaller spacecraft, having higher cross-section area to inertia ratio, exhibit higher frequencies and are particularly suited for this method. The method described in this paper can provide global cross-track and in-track wind measurements. The measurements accuracy and spatial resolution with respect to the system parameters are analyzed and discussed for an ideal one rotational degree-of-freedom case.