Doppler Tracking

Doppler tracking is a sophisticated technique widely employed in satellite tracking and orbit determination, enabling precise measurement of a satellite’s velocity and position in space. This method relies on the observation of the Doppler shift in the frequency of signals transmitted by the satellite and received by ground-based tracking stations.

As a satellite moves in its orbit, its velocity relative to the tracking station causes a change in the frequency of the transmitted signals due to the Doppler effect. When the satellite is moving toward the tracking station, the received frequency is higher than the transmitted frequency, resulting in a positive Doppler shift. Conversely, when the satellite is moving away from the station, the received frequency is lower than the transmitted frequency, leading to a negative Doppler shift.

By analysing the magnitude and direction of the Doppler shift, ground-based tracking stations can precisely determine the satellite’s speed and radial distance at any given moment. This information, along with additional data from multiple tracking stations, allows for accurate computation of the satellite’s position and orbit parameters.

Sources:

• NASA – Range and Doppler Tracking Observables
• European Space Agency – Direct ground to Spacecraft ranging
• NASA – Ocean Surface Topography from Space