A comparison of R1 and R4 IVS networks S.B. Lambert, Royal Observatory of Belgium, formerly at NVI,...

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)