Atomic Clock

An atomic clock is a highly precise timekeeping device that uses the stable frequency of electromagnetic radiation emitted or absorbed during transitions between energy levels of atoms (commonly cesium or rubidium). In geodesy, atomic clocks are fundamental for precise time and frequency standards required for Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and other space-geodetic techniques. Accurate timing at the nanosecond level enables precise positioning, Earth rotation measurements, reference frame realization, and the monitoring of temporal variations in the Earth system.