Using Satellite Laser Ranging (SLR) data from LAGEOS and LAGEOS 2 and the new generation Earth gravity field models generated from data of the space missions CHAMP and GRACE, Ciufolini and Pavlis [2004] detected the Lense’Thirring (L-T) effect predicted by Einstein’s General Relativity (GR). Precise analysis of about a decade of LAGEOS and LAGEOS 2 data resulted in an accurate measurement using the EIGEN-2S, GGM01S, and EIGEN-GRACE02S models. The new analysis is in agreement with earlier results using less accurate gravity models, yet far more accurate and especially more robust thanks to the unprecedented accuracy improvement of the gravitational models with the GRACE data. The test using the nodal rates of the two satellites and the EIGEN-GRACE02S gravity model had an estimated total error between 5% and 10% of the GR prediction. As of early 2008, Ciufolini was successful in proposing to the Italian Space Agency (ASI), the launch of a satellite similar in design to the two LAGEOS, the LAser Relativity and Earth Science - LARES mission, with primary goal an even more precise L-T measurement. LARES, originally proposed to ASI a decade ago, had completed phase A, but was never given the opportunity to continue beyond that step until recently. All of those on this team were named co-PIs on the original ASI proposal as well as the recent, successful one. With GRACE data nearing a complete six-year data set, a new mean field GGM03 just recently released, and a new ESA geopotential mapping mission GOCE to be launched in early 2009, we expect very soon a much more accurate gravity model. This warrants the re-examination of the original LAGEOS and LAGEOS 2 data, in this case extended by the data soon to be collected on LARES. The successful utilization of the LARES data set relies on the proper calibration of the satellite, its dynamics, the development of appropriate reduction models and techniques and the analysis of the collected data. Although similar in design to LAGEOS, LARES is not a clone and it is an orbit different from either of the two LAGEOS. LARES will be launched with VEGA, on its inaugural launch. This limits the altitude of the mission to some 1500 km (vs. 6000 km for the LAGEOS). To compensate for the lower altitude, the s/c has been redesigned a size half as large as the LAGEOS to minimize the effect of drag. At the same time, the mass of the s/c has been maximized by use of an alloy of almost pure Tungsten. The LARES area-to-mass ratio is only 36% that of LAGEOS. This will result in improved orbital accuracy despite the lower LARES altitude and the residual atmospheric influence at that altitude. Our proposal intends to contribute unique expertise in the following efforts in connection to the LARES mission: a. develop accurate dynamical models for robust and precise orbit determination with SLR data, with special attention to relativistic modeling errors affecting the L-T signal embedded in the SLR data b. re-analyze the entire LAGEOS, LAGEOS 2 and LARES data set for a new L-T result with a well-calibrated estimate of the accuracy of the results c. utilize the LARES data set for Earth science applications such as the terrestrial reference frame The first item will primarily cover activities in the first year of the investigation while the second and third items will cover the period of the primary phase of the mission (nominally three years) and beyond. Following the main phase, we will document the collected data and the so far obtained results and archive all of the data and derived products at NASA and ASI archives. The proposing team will seek the collaboration with additional agencies, institutions and individuals who will either express interest in the project or have expertise in areas of interest to this investigation.

Project PI: Erricos Pavlis/University of Maryland, Baltimore County

Acad IV-A Rm 114 UMBC 1000 Hilltop Circle Baltimore MD 21250 US

Phone: (410) 455-5832

Fax: (410) 455-1893



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Started: Sep 27, 2010

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