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1

Testing impact of the strategy of VLBI data analysis on the estimation of Earth Orientation Parameters and station coordinates

Wielgosz A., Tercjak M., Brzeziński A.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 101

1--15

EN

Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable to realise the Celestial Reference Frame and tie it with the Terrestrial Reference Frame. It is also the only technique, which measures all the Earth Orientation Parameters (EOP) on a regular basis, thus the role of VLBI in determination of the universal time, nutation and polar motion and station coordinates is invaluable. Although geodetic VLBI has been providing observations for more than 30 years, there are no clear guidelines how to deal with the stations or baselines having significantly bigger post-fit residuals than the other ones. In our work we compare the common weighting strategy, using squared formal errors, with strategies involving exclusion or down-weighting of stations or baselines. For that purpose we apply the Vienna VLBI Software VieVS with necessary additional procedures. In our analysis we focus on statistical indicators that might be the criterion of excluding or down-weighting the inferior stations or baselines, as well as on the influence of adopted strategy on the EOP and station coordinates estimation. Our analysis shows that in about 99% of 24-hour VLBI sessions there is no need to exclude any data as the down-weighting procedure is sufficiently efficient. Although results presented here do not clearly indicate the best algorithm, they show strengths and weaknesses of the applied methods and point some limitations of automatic analysis of VLBI data. Moreover, it is also shown that the influence of the adopted weighting strategy is not always clearly reflected in the results of analysis.

2

Extreme learning machine for the predictions of length of day

Lei Y., Zhao D., Cai H.

Artificial Satellites : Journal of Planetary Geodesy

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2015

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Vol. 50, No. 1

19--33

EN

This work presents short- and medium-term predictions of length of day (LOD) up to 500 days by means of extreme learning machine (ELM). The EOP C04 time-series with daily values from the International Earth Rotation and Reference Systems Service (IERS) serve as the data basis. The influences of the solid Earth and ocean tides and seasonal atmospheric variations are removed from the C04 series. The residuals are used for training of the ELM. The results of the prediction are compared with those from other prediction methods. The accuracy of the prediction is equal to or even better than that by other approaches. The most striking advantages of employing ELM instead of other algorithms are its noticeably reduced complexity and high computational efficiency.

3

The ILRS EOP time series

Sciarretta C., Luceri V., Pavlis E. C., Bianco G.

Artificial Satellites : Journal of Planetary Geodesy

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2010

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Vol. 45, No. 2

41--48

EN

Since 2004, ILRS has been providing on a weekly basis combined SSC/EOP solutions from 7-day arcs to support IERS for EOP computation and reference frame maintenance. At present, eight Analysis Centers and two Combination Centers contribute to the weekly official ILRS combined solution from which the main SLR contribution to the IERS EOP reference series is derived. The most recent work performed jointly by all ILRS Analysis Centers (AC) was the generation of a contribution to the next ITRF, extending the time-span coverage of the 7-day arcs combined solution to 1983-2008. In another effort we try to improve the ILRS products’ latency and to minimize the delay of the SLR contribution to the IERS EOP estimation, by increasing the product generation frequency (pre-operational daily product), to once per day.

4

Russian State Time and Earth Rotation Service: observations, EOP series, prediction

Kaufman M., Pasynok S.

Artificial Satellites : Journal of Planetary Geodesy

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2010

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Vol. 45, No. 2

81--86

EN

Russian State Time, Frequency and Earth Rotation Service provides the official EOP data and time for use in scientific, technical and metrological works in Russia. The observations of GLONASS and GPS on 30 stations in Russia, and also the Russian and worldwide observations data of VLBI (35 stations) and SLR (20 stations) are used now. To these three series of EOP the data calculated in two other Russian analysis centers are added: IAA (VLBI, GPS and SLR series) and MCC (SLR). Joint processing of these 7 series is carried out every day (the operational EOP data for the last day and the predicted values for 50 days). The EOP values are weekly refined and systematic errors of every individual series are corrected. The combined results become accessible on the VNIIFTRI server (ftp.imvp.ru) approximately at 6h UT daily.

5

An influence of wide-band oscillations in pole coordinates caused by atmospheric, ocean and hydrology excitation functions on their prediction errors

Kosek W, Popiński W., Rzeszótko A.

Reports on Geodesy

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2008

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z. 2/85

37-47