Estimation of Temporal Variations in the Earth’s Gravity Field Using Novel Optical Clocks Onboard of Low Earth Orbiters

The current generation of optical atomic clocks has reached a fractional frequency uncertainty of 1 $$\times $$ × 10 $$^{-18}$$ − 18 (and beyond) which corresponds to a geopotential difference of 0.1 m $$^{2}$$ 2 /s $$^{2}$$ 2 . Those gravitational potential differences can be observed as gravitational redshift when comparing the frequencies of optical clocks. Even temporal potential variations might be determined with precise novel optical atomic clocks onboard of low-orbiting satellites such as SLR-like (e.g. LAGEOS-1/2) and GRACE-like missions. In this simulation study, the potential of precise space-borne optical clocks for the determination of temporal variations of low-degree Earth’s gravity field coefficients are investigated. Different configurations of satellite orbits, i.e. at different altitudes (between 400 and 6000 km) and inclinations, are selected as well as certain assumptions on the clock performance are made. A particular focus is put on how well degree-2 coefficients can be estimated from those optical clock measurements and how it compares to results from SLR.