Definition
Time measurements with subnanosecond accuracy and associated precise frequency measurements are major contributors to the space geodetic techniques and to the determination of the geoid.
Introduction
Time and frequency metrology has been a cornerstone of the development of space geodetic systems. The high accuracy offered by Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), or Doppler Orbitography by Radiopositioning Integrated on Satellite (DORIS) is directly derived from the accuracy and stability of onboard and/or ground atomic clocks. This chapter summarizes the notions of time and frequency, the types of atomic clocks, their comparison techniques, and their applicability in geodesy.
Some Notion of Time and Frequency: Stability, Time, Frequency, and Clock
What we call a clock is an oscillator providing as output a sinusoidal voltage variation with a frequency ν0 and amplitude V0. From this frequency, the...
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Defraigne, P. (2022). Precise Time and Frequency in Geodesy. In: Sideris, M.G. (eds) Encyclopedia of Geodesy. Encyclopedia of Earth Sciences Series. Springer, Cham. https://doi.org/10.1007/978-3-319-02370-0_14-1
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DOI: https://doi.org/10.1007/978-3-319-02370-0_14-1
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