Long‐period perturbations in starlette orbit and tide solution

Abstract

Continuous and dynamically consistent orbits have been computed using satellite laser ranging (SLR) data to Starlette for a one-year period during 1976 and 1977 and the three-year period from 1983 through 1985. A low degree and order ocean tide solution, consisting of a total of 66 tidal parameters from 14 tidal constituents, was obtained in a combined solution using both the one-and three-year Starlette orbits. An enhanced model of the Schwiderski [1980] tide solution was used both as the a priori and the background tide model. The model contains 368 tidal coefficients from 21 tidal constituents. Yearly values for the second-degree annual tides, St, which produce seasonal variations on the Starlette node, were obtained also. These variations were found to have year-to-year fluctuations of more than 25% about the mean value and produced significant long-period perturbations in the Starlette orbit. The Starlette tide solution is in good agreement with the Schwiderski tide solutions and with other satellite solutions, including multi-satellite tide solutions. The average uncertainties are approximately 0.1 cm for the estimated semidiurnal and diurnal tides and 0.4 cm for the long-period tides. The discrepancies of effective k•. inferred from the Starlette tide solution and other tide solutions are less than 0.01. The tide solutions were evaluated using orbit fits of a three-year LAGEOS and a one-year Starlette long are. The results indicate that the Starlette tide solution produces significantly improved orbit fits for both LAGEOS and Starlette. The uncertainties for the estimated tide model coefficients were used to predict tidal errors for the LAGEOS orbit and were found to be consistent with the apparent tidal errors present in this orbit. The computed secular change in the Moon's mean motion due to tidal dissipation is-24.8+0.8 are second/century 2, which is in good agreement with the results obtained from other investigations. INTRODUCr•oN the ascending node and one cycle of the dominant K• ocean tide Advances in the precision of satellite laser ranging (SLR) perturbation is about 91 days. observations to near-Earth geodetic satellites have contributed The largest source of error limiting the accuracy of the Starlette significantly to the fields of geodetic and geodynarrdc research. orbit is ntismodeling of the Earth's gravity field. A Starlette-Two geodetic satellites, LAGEOS and Starlette, have been tailored gravity field model, PGS-1331, was developed using excellent tools for such studies. In particular, precise Starlette data collected from 1975 through 1978 in combination determinations for Earth rotation parameters, baseline motions, with the GEM-9 normal equations by Marsh et al. [1985]. The and station coordinates defining the conventional terrestrial range residuals for five-day Starlette orbits were at the 60-70-cm system have been obtained from SLR measurements to the level using this gravity field. Since then, improved Earth gravity LAGEOS satellite. The LAGEOS-derived Earth rotation field models...

Temporal Variations of the Earth Gravity Field For 1985-1989 Derived From Lageos

“…Christodoulidis et al 1988;Cheng et al 1990) show quite large amplitude and considerable variability, likely due to contamination of climatological effects, so that these can hardly be used to estimate any departure from equilibrium. The semi-annual ocean tide determined by Schwiderski (1980) estimate is based on the difference between the Schwiderski's model and satellite-derived estimates (Christodoulidis et al 1988;Cheng et al 1990) for the dominant degree-2 term of the tidal-spherical-harmonic expansion, since at the semi-annual frequency, climatological effects may be less important. Because c3,, is mostly recovered from eccentricity perturbations, errors due to nongravitational forces mismodelling may seriously affect the c,, determination.…”

Earth Rotation Variations – Long Period

“…Of primary importance in this regard is the value for the tidal acceleration _ n of the Moon since it controls the long-term behavior of the Moon's motion. Other SLR-derived values for _ n have been reported by Cheng et al (1990Cheng et al ( , 1992, Marsh et al (1990Marsh et al ( , 1991, Dickman (1994), Lerch et al (1994), and Ray (1994). Tidal forces distort the figure of the Earth and hence its gravitational field, which in turn perturbs the orbits of artificial satellites.…”

METRIC: A Dedicated Earth-Orbiting Spacecraft for Investigating Gravitational Physics and the Space Environment

“…In this respect, the dynamical environment that METRIC will encounter is much more similar to the one faced by Starlette [18]. This implies a remarkable sensitivity to a spectrum of solid and ocean tides and in turn points to interesting possibilities for improving our knowledge of tides and, more in general, mid-to high-wavelength features of the Earth's gravity field.…”