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A comparison of R1 and R4 IVS networks S.B. Lambert, Royal Observatory of Belgium, formerly at NVI, Inc./US Naval Observatory A.-M. Gontier, Paris Observatory

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Two parallel networks running since 2002 Overview of the networks R1 (Mondays), 13 sitesR4 (Thursdays), 10 sites

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Overview of the networks R1 (Mondays), 13 sitesR4 (Thursdays), 10 sites Question: are the networks consistent? Can they realize identically EOP and reference systems?

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Overview of the networks R1 (Mondays), 13 sitesR4 (Thursdays), 10 sites > 10,000GILCHARTMATENYALONSATSUKWESTWETTGILCKOKEMATETSUKWESTWETTGILCNYALTSUKWESTWETTGILCTSUKWESTWETT 5, ,000ALGOKOKEHARTSESHTIGOHARTKOKEMEDISESHTIGOHARTHOBAKOKEMEDIONSATIGO < 5,000MEDI TIGO HOBA MEDI NYAL HOBA ONSA NYAL SESH SVET > 10,000ALGOGILCKOKENYALWETTALGOFORTGILCKOKEMATENYALWETTALGOGILCKOKENYALSVETWETTALGOFORTGILCKOKENYALSVETWETT 5, ,000FORTFORT < 5,000HOBA MATE SESH ONSA SVET TIGO TSUK MEDI ONSA TIGO HART MEDI TIGO

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Sensitivity of a baseline to Earth orientation, where X, Y and Z are the station coordinates: “permanent” network all sites EOP and baseline geometry x y UT1

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Description of the solution Solution run with R1 sessions only, then with R4 sessions only Global: site positions and velocities, antenna axes, source positions Arc: polar motion and rate, UT1-UTC and rate, nutation offsets NNR and NNT on all sites except MEDICINA and GILCREEK (known episodic motions) NNR on 212 ICRF defining sources Made with CALC/SOLVE software Compared against IERS Bulletin A (USNO combined solution)

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Comparison of EOP solutions Difference to IERS Bulletin A, mean standard error about 300 as

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Comparison of TRF 7-parameter Helmert transformation to compare individual TRF against ITRF Number of sites R1R4

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What shows up in operational series? Difference to IERS Bulletin A, standard error about 300 as

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Conclusion Compares the 2 parallel 24-hour R1 and R4 networks run by the IVS Looks at the possible influence of geometry, EOP and TRF realizations Evolution of R1 between 2002 and 2005 greatly improved the R1 series : sites in the southern hemisphere after 2003 Current R1 and R4 residuals against IERS Bulletin A have same standard deviation R1 network more extended than R4 but with a reduced East-West “permanent” network R4 smaller but “permanent” R1-derived TRF closer to ITRF than R4-derived TRF but with larger uncertainties Inconsistencies show up in operational series (drift of 30 as per year)

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