Estimating the TIMED Satellite Drag Using the Solar EUV Experiment (SEE) Measurements

The Solar EUV Experiment (SEE) aboard the TIMED spacecraft nominally measures the solar irradiance from 0.1-193 nm and has been operating from January 2002 to the present. The orientation of TIMED provides a stable, nearly constant view factor to the ram direction. Together, the TIMED orientation and SEE measurements provide a unique opportunity to determine the influence of the solar radiation on satellite drag. This paper presents the first results of this high altitude upper atmospheric satellite drag study including: determining precision orbital changes of the TIMED spacecraft using the on-board GPS navigation system, validation of the drag estimate, identifying the key wavelength ranges in the solar spectrum that affect the orbit changes, and creation of a solar irradiance index from those wavelengths that is representative of the atmospheric drag experienced by TIMED.