Miłosława Rutkowska

Estimation of the Elastic Earth Parameters Using SLR Data for the Low Satellites STARLETTE and STELLA

In this paper we present estimated values for the global elastic parameters (k2, k3) and (h2, l2) derived from the analysis of Satellite Laser Ranging (SLR) data. We analyse SLR data for two low satellites, STARLETTE and STELLA, collected over a period of two years, from 1 January 2005 to 1 January 2007, from 18 globally distributed ground stations. We carry out a sequential analysis for the two satellites jointly, and study the stability of the estimates as a function of the length of the data set used. The adjusted final values of (k2, k3) and (h2, l2) for STARLETTE and STELLA are compared to, and are largely found to support, the estimates we previously published based on data for two high satellites LAGEOS 1 and LAGEOS 2. A major discrepancy between the two solutions was only found for the Shida number l2.

Orbit analysis of the satellite westpac

Abstract This paper addresses the computation of the orbit of the satellite WESTPAC, which was launched on July 10, 1998, into a circular orbit at an altitude of 835 km and with an inclination of 98 degrees. To obtain a high-quality orbit solution, all forces acting on the satellite need to be modelled as accurately as possible. This paper discusses the influence of the modelling of different physical effects on the motion of WESTPAC, in particular in terms of orbit quality. The study is based on observations taken by the global network of laser stations during the period from August 1, 1998, until March 30, 1999. In this study, a number of test cases are defined and investigated, focussing on optimum orbit quality. The latter is assessed by looking at the (weighted) rms-of-fit, the orbit overlaps of successive data arcs and the stability of independent solve-for parameters. The investigation has resulted in a “best” scenario which includes the following elements: the GRIM-5S1 gravity field solution, the MSIS86 model for atmospheric density, the GOT99.2 ocean tides model, drag coefficients solved-for at 12-hour intervals, and one set of 1-cpr accelerations in the along-track and cross-track directions. This scenario gives a fit of the laser range observations of 3.7 cm and an orbit quality of about 5, 10 and 20 cm in the radial, cross-track and along-track directions, respectively.

Improvement of the SLR Borowiec station position in the global network ITRF91

Abstract This paper describes briefly two station coordinates solutions, the first one computed at Space Research Centre (SRC) using tracking data from Lageos satellite, and the second one computed at European Space Operations Centre (ESOC) using tracking data from Lageos 1, ERS-1 and TOPEX/Poseidon in a multi-arc solution. In particular the solution computed for the Borowiec station in ITRF91 system is described extensively. The Borowiec station position was estimated simultaneousely, considering or not the existence of range biases, with other geophysical parameters such as: daily polar motion parameters x p , y p , ocean tide coefficients, earth gravitational constant GM, etc.

SLR Technique Used For Description Of The Earth Elasticity

Abstract We present estimated values for the global elastic parameters (h2, l2) derived from the analysis of Satellite Laser Ranging (SLR) data. We analyse SLR data for LAGEOS 1 and LAGEOS 2 and for two low satellites, STARLETTE and STELLA, collected over a period of 2.5 years, from January 1 2005 to July 1 2007, from 18 globally distributed ground stations. The adjusted final values (h2, l2) for all satellites are compared. A major discrepancy between the two solutions was only found for the Shida number l2. Computations were performed using GEODYN II NASA/GSFC software. The following analysis is the continuation of our research published in Jagoda and Rutkowska (2013); that analysis was conducted separately for the two low satellites, STELLA and STARLETTE (separately for STELLA and separately for STARLETTE) whereas in this study we present the results of determining h2 and l2 parameters obtained from the joint observation of the STELLA and STARLETTE satellites (STARLETTE + STELLA) and joint observation of high satellites: LAGEOS 1 and LAGEOS 2 (LAGEOS 1 + LAGEOS 2). The combination of the observation aims at an increased stability of the estimates and reduced errors of the means of the parameters being determined.

Analysis of 1993–1995 Borowiec SLR data: Station positioning and range bias computation

Abstract The Borowiec station takes part in international geodetic and geodynamics research programmes such as IERS, WEGENER, IGS, BSL, EUREF etc. The main purpose of this activity is the establishment of a well-defined reference point within Poland, which may be used to connect local geodetic networks to the global network. This is only possible by virtue of the fact that Borowiec is equipped with modern measurement facilities: a third generation SLR system and a new GPS receiver. This paper briefly describes the computation of four station coordinate solutions, based on SLR data. The solutions 1 and 2 are computed at the Space Research Centre in Warsaw using tracking data from the satellite Lageos-1 only over five periods (August–December 1993, January–February 1994, July–November 1994, January–February 1995 and May–July 1995) produced by 17 “good” stations (given in section 2). The solutions 3 and 4 are computed at Delft University of Technology, Faculty of Aerospace Engineering, using tracking data from both Lageos-1 and Lageos-2 produced by 56 stations covering the period 1993–1995 entirely. The solutions 2 and 4 consider the estimation of range biases simultaneously with the station position for Borowiec only and for all stations, respectively. The solution of the range bias amounts to approximately −30mm on average, which has an effect of about 20mm on the solution for the station position. The position solutions computed in Warsaw and Delft are consistent to about 20mm.

Time changes of the potential Love tidal parameters k2 and k3

The planet Earth is continuously changing in time, so there are phenomena that require continuous observation, including tidal parameters. The main goal of this study is to analyze time changes of the Love potential tidal parameters. This paper concerns an analysis of the estimated Love numbers k for the second and the third degree tides (numbers k2 and k3), associated with the tide variations of the satellite motion. The measured data used for determining the parameters k2, k3 were conducted within the period of January 1, 2014 until July 1, 2016 by LAGEOS-1 and LAGEOS-2 satellites. The results were compared with our previous determination of these parameters from LAGEOS data during the period from January 1, 2005 until July 1, 2007 to examine whether any systematic differences and time evolution occur. The adjusted values for k2 equalling 0.29842 ± 0.00008 and k3 equalling 0.0901 ± 0.0034 are discussed and compared with the nominal values given in International Earth Rotation and Reference Systems Service standards. The differences between the k2 and k3 values obtained for the time interval 2005.0–2007.5 and the results for 2014.0–2016.5 interval are –0.00288 for k2 and 0.0042 for k3. The obtained differences in the k2 and k3 values may indicate their evolution in time.

Tectonic Plate Parameters Estimated in the International Terrestrial Reference Frame ITRF2008 Based on SLR Stations

This paper concerns an analysis of the accuracy of estimated parameters Ω (Φ, Λ, ω) which define the tectonic plate motions. The study is based on the velocities of station positions published by ITRF2008 for Satellite Laser Ranging (SLR) technique. The Eurasian, African, North American and Australian plates were used in the analysis. Influence of the number and location of stations on the plate surface on estimation accuracy of the tectonic plate motion parameters was discussed. The results were compared with the APKIM 2005 IGN model. In general, a remarkable concurrence agreement between our solutions and the APKIM 2005 model was found.