a comparison of r1 and r4 ivs networks s.b. lambert, royal observatory of belgium, formerly at nvi,...
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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
Two parallel networks running since 2002
Overview of the networks
R1 (Mondays), 13 sites R4 (Thursdays), 10 sites
Overview of the networks
R1 (Mondays), 13 sites R4 (Thursdays), 10 sites
Question: are the networks consistent?Question: are the networks consistent?
Can they realize identically EOP and reference systems?Can they realize identically EOP and reference systems?
Overview of the networks
R1 (Mondays), 13 sites R4 (Thursdays), 10 sites
2002 2003 2004 2005
> 10,000 GILCGILC
HARTHART
MATEMATE
NYALNYAL
ONSAONSA
TSUKTSUK
WESTWEST
WETTWETT
GILCGILC
KOKEKOKE
MATEMATE
TSUKTSUK
WESTWEST
WETTWETT
GILCGILC
NYALNYAL
TSUKTSUK
WESTWEST
WETTWETT
GILCGILC
TSUKTSUK
WESTWEST
WETTWETT
5,000-10,000
ALGOALGO
KOKEKOKE
HARTHART
SESHSESH
TIGOTIGO
HARTHART
KOKEKOKE
MEDIMEDI
SESHSESH
TIGOTIGO
HARTHART
HOBAHOBA
KOKEKOKE
MEDIMEDI
ONSAONSA
TIGOTIGO
< 5,000 MEDI
TIGO
HOBA
MEDI
NYAL
HOBA
ONSA
NYAL
SESH
SVET
2002 2003 2004 2005
> 10,000 ALGOALGO
GILCGILC
KOKEKOKE
NYALNYAL
WETTWETT
ALGOALGO
FORTFORT
GILCGILC
KOKEKOKE
MATEMATE
NYALNYAL
WETTWETT
ALGOALGO
GILCGILC
KOKEKOKE
NYALNYAL
SVETSVET
WETTWETT
ALGOALGO
FORTFORT
GILCGILC
KOKEKOKE
NYALNYAL
SVETSVET
WETTWETT
5,000-10,000
FORTFORT FORTFORT
< 5,000 HOBA
MATE
SESH
ONSA
SVET
TIGO
TSUK
MEDI
ONSA
TIGO
HART
MEDI
TIGO
Sensitivity of a baseline to Earth orientation, where X, Y and Z are the station coordinates:
“permanent” network all sites
EOP and baseline geometry
xX 2 Z 2
yY 2 Z 2
UT1UTC
X 2 Y 2
x
y
UT1
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)
Comparison of EOP solutions
Difference to IERS Bulletin A, mean standard error about 300 as
Comparison of TRF
7-parameter Helmert transformation to compare individual TRF against ITRF
Number of sites
R1 R4
What shows up in operational series?
Difference to IERS Bulletin A, standard error about 300 as
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 deviationCurrent 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 uncertaintiesR1-derived TRF closer to ITRF than R4-derived TRF but with larger uncertainties
• Inconsistencies show up in operational series (drift of 30 Inconsistencies show up in operational series (drift of 30 as per year)as per year)