Assessments of the Accuracy of Global Geodetic Satellite Laser Ranging Observations During the Last Decade and Potential Impact on ITRF Scale
Monday, 15 December 2014: 8:45 AM
We continue efforts to estimate the intrinsic accuracy of range measurements made by the major satellite laser ranging stations of the ILRS Network using normal point observations of the primary geodetic satellites LAGEOS and LAGEOS-II. In a novel approach we carry out weekly reference frame solutions for satellites’ initial state vectors, station coordinates and daily EOPs (X-pole, Y-pole and LoD), as well as estimating range bias for each of the stations. We apply known range errors a-priori from the table developed and maintained through the efforts of the ILRS Analysis Working Group and apply station- and time-specific satellite centre of mass corrections (Appleby and Otsubo, 2014), both corrections that are currently implemented in the standard ILRS reference frame products. Our new approach, to solve simultaneously for station coordinates and range bias for all the stations, has the strength that such bias results that are discovered are independent of the coordinates taken for example from ITRF2008; thus this approach has the potential to determine range errors that may have become absorbed primarily in station height had the coordinates been determined on the assumption of zero bias. A possible weakness of the approach is that correlations will inevitably exist between station height and range bias, and a clear separation may not be possible. However, for the major stations of the Network, and using LAGEOS and LAGEOS-II observations simultaneously to determine a single mean bias for each station in the weekly solutions, we do perform a partial separation between these parameters at the expense of an increase in the variance of the stations’ height time series. In this paper we discuss the results in terms of impact on coordinate solutions and on the scale of the reference frame, and in the context of preparations for ITRF2013.