Analysis of earth rotation solution from Starlette

Abstract

In this study, a consider covariance analysis of error sources limiting the accuracy of the Earth rotation parameters (ERP), which include the polar motion coordinates x and y and the length of the day (LOD), determined from satellite laser ranging (SLR) data to near‐Earth geodetic satellites, has been performed. The solution for the ERP has been obtained from the analysis of the SLR data to Starlette collected primarily during the 14‐month MERIT Campaign that began September 1, 1983. A preliminary Starlette ERP solution based on a Starlette‐tailored Earth gravity model, PGS 1331, was compared with the solutions derived from SLR to LAGEOS, and the weighted rms about the mean of the difference between these solutions was 13 milliarcseconds (mas), 11 mas, and 0.6 milliseconds (ms) for Δx, Δy, and ΔLOD, respectively. A covariance analysis indicated that the accuracy of the Starlette ERP solution was limited primarily by errors in the Earth's gravity field model. In particular, this analysis showed that the first‐order geopotential coefficients produced a systematic perturbation in the solutions for x and y with a maximum value up to 29 mas and a dominant period of 74 days. The LOD determination by Starlette is limited primarily by errors in the Earth's zonal harmonics and long‐period tides. With the improvement of the Starlette force model by simultaneous estimation of selected geopotential coefficients and ocean tide parameters, the weighted rms of the Starlette solution with respect to LAGEOS was reduced to 9 mas and 6 mas for Δx and Δy, respectively. However, this technique was not able to improve the accuracy of the LOD solution. Using an improved gravity field recently developed at the University of Texas Center for Space Research, the weighted rms differences between Starlette and LAGEOS ERP solutions have been further reduced to 4.4 mas and 3.6 mas for Δx and Δy, respectively. These results show that a significant improvement of the ERP solution from Starlette can be achieved through further refinements in the Earth's gravity field and tide model and that a precision of <5 mas in x and y coordinates of the pole is feasible from Starlette.

Contribution of Starlette, Stella, and AJISAI to the SLR-derived global reference frame

“…The pole coordinates from the LEO solutions are worse in terms of the weighted RMS by a factor 1.6 than the estimates derived from the LAGEOS solutions. Schutz et al (1989) reported that the best obtained pole coordinates from Starlette data agreed within 4.4 and 3.6 mas for the X pole and the Y pole, respectively, with values obtained from LAGEOS-1 observations. The agreement of pole coordinates between LEO and LAGEOS solutions in this analysis is at the level of 0.2 mas.…”

“…Therefore, the satellite is equipped with curved mirrors covering the large satellite surface in addition to the embedded laser-dedicated retroreflectors. Schutz et al (1989) demonstrated the potential of Starlette for the determination of ERP. At that time, the best pole coordinates from Starlette agreed within 4.4 and 3.6 mas for the X and Y coordinates of the pole, respectively, with values obtained from LAGEOS-1 observations.…”

Experiments in tidal mass conservation

“…Those differences are at a level currently detectable by space-geodetic measurement techniques (e.g. Robertson et al 1985;Schutz et al 1989).…”

LAGEOS Sensitivity to Ocean Tides

“…Satellite Laser Ranging (SLR) greatly contributes to deriving various geodetic and geophysical parameters (Smith and Turcotte 1993), e.g., to deriving Earth orientation parameters (Schutz et al 1989, static and time-variable Earth's gravity field (Cheng et al 1997, Bianco et al 1998, Maier et al 2012, station coordinates and velocities (e.g., Wnuk 2003, Lejba andSchillak 2011), crustal deformations (Schillak et al 2006), and elastic Earth parameters Jagoda 2010, 2012). The orbits of LAGEOS satellites equipped with laser retro-reflectors can be very well determined through the SLR observations with the accuracy at a level of a few millimeters, as well as through the minimized area-to-mass ratios of LAGEOS, and, as a consequence, a minimized impact of nongravitational orbit perturbations.…”