Temporal variations in low degree zonal harmonics from Starlette orbit analysis

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Abstract
The dynamical effect of temporal variations in the zonal harmonics of the Earth's gravitational potential due to tidal and meteorological mass redistribution has been observed using satellite laser ranging (SLR) measurements to Starlette. The secular variations in the Earth's zonal harmonics, , and the year‐to‐year fluctuation of the even degree annual and semi‐annual tides (Sa and Ssa) have been determined from a continuous Starlette orbit spanning from 1983 through 1985. When variations in higher degree zonals are assumed to be zero and the 18.6‐year tide is fixed to an equilibrium value, the results are: , , , in units of 10−11 yr−1. The Starlette‐derived is in good agreement with the value observed from Lageos and values predicted from postglacial rebound. The mean values for Sa and Ssa tides are in good agreement with other tide solutions. The year‐to‐year fluctuations of the even degree Sa, deduced from Starlette node variations, are about 25% of the mean value obtained during the three‐year Starlette orbit span.