Meteorological data and effects on VLBI geodetic parameters
Abstract
Pressure and temperature impact VLBI processing in two different ways: the pressure is used to calculate the zenith hydrostatic delay and the temperature is used to calculate the linear expansion of the telescope components. However these two significant parameters are not systematically measured onsite. Hence the analysts have to use different sources of meteorological data: observations recorded by other met sensors in the neighborhood of the VLBI antenna (GPS network for example) or data from a model. This inhomogeneity in the data cause discontinuities and/or biases in the global time series of meteorological data which alter significantly the VLBI solutions. In a previous study, it has been shown that a bias in pressure of 10mbar for the station Svetloe affects the determination of the vertical component up to 1.2mm. A 9-year period of missing pressure for the station Westford affects the weighted RMS up to 1mm when using a constant default value in the software Calc/Solve. The VLBI group at Goddard Space Flight Center produces homogeneous time series of pressure and temperature calculated from the ERA Interim data of the European Center for Medium-Range Weather Forecasts (ECMWF). These time series cover the entire VLBI observation period (1979-2018) for all VLBI sites, are updated regularly and are available on the VLBI Temperature and Pressure Service webpage (https://vlbi.gsfc.nasa.gov/services/met/). The grid initially used was a 1.5 x 1.5 degree equal angular grid for the entire Earth. We recently updated our time series using the best available grid which is now 0.125 x 0.125. This presentation shows the impact on the VLBI solutions when using these series.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G33C0696L
- Keywords:
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- 1229 Reference systems;
- GEODESY AND GRAVITYDE: 1299 General or miscellaneous;
- GEODESY AND GRAVITY