How did tracking Sputnik 1 help scientists develop the idea of satellite navigation?

In 1957, scientists tracking Sputnik 1 discovered that they could precisely plot the satellite's orbit by analyzing the Doppler shift in its transmitted radio signals relative to a fixed location on Earth.1

This observation provided a foundational insight: if the process were reversed—meaning the orbits of satellites were known with high precision—an observer on Earth could determine their own location by measuring the Doppler shift of signals received from those satellites. This realization was a critical step in the development of early satellite-based navigation systems, such as the U.S. Navy's Transit system in the 1960s. While modern GPS technology has evolved to use signal travel time and atomic clocks rather than relying solely on Doppler shifts for positioning, the initial tracking of Sputnik 1 proved that artificial satellites could serve as reliable reference points for global navigation.12