Stability of the extragalactic VLBI reference frame

Gontier, A. M.; Bail, K. Le; Feissel, M.; Eubanks, T. M.

doi:10.1051/0004-6361:20010707

Cited by 36 publications

(31 citation statements)

References 8 publications

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“…4 and 5 in the form of wavelet analysis . Figure 4, which considers all sources (Conventional approach), shows energy in the 1984-1990 time frame that disappears after 1990, in agreement with the Gontier et al (2001) stability diagnosis mentioned in Sect. 5.…”

Section: Prograde Ficnsupporting

confidence: 82%

“…Note that perturbation induced by the 163 unstable sources alone is not particularly large. Gontier et al (2001) have shown that the general improvements in VLBI technology and observing strategies brought the astrometric results to their current precision towards the end of the 1980's. Starting about 1990, individual source coordinates stabilised.…”

Section: Precession and Obliquity Ratementioning

confidence: 99%

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Sidereal orientation of the Earth and stability of the VLBI celestial reference frame

Feissel-Vernier

Ma²,

Gontier

et al. 2005

A&A

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Abstract. The consideration of time stability of extragalactic radio sources observed by VLBI is shown to allow the realisation of more consistent celestial reference frames. The impact on the estimation of precession and nutation components is investigated over the time span [1984][1985][1986][1987][1988][1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002]. The precession correction to the IAU 2000 value that is obtained when excluding the unstable sources reaches 49 ± 5 µas/year, to be compared to 12 ± 5 µas/year using the current conventional celestial frame. The determination of the obliquity rate is unaffected and remains at the level of 27 ± 2 µas/year. The observed correction to the 18.6-year nutation amplitude using the current conventional celestial frame ie sizeably corrupted by the unstable sources. After accounting for this effect, the estimations relative to both sets of reference radio sources confirm a discrepancy with the IAU 2000 nutation model with a total amplitude of 320 ± 100 µas for the observed nutation in longitude, to be compared to the 80 µas discrepancy found by Mathews et al. (2002, JGRB, 107, 1029. The discrepancy in obliquity amounts to 50 ± 16 µas. The effect of source instability is shown to have an impact on the determination of universal time at the one microsecond level. The high and medium frequency nutation terms (up to periods of a few years) are impacted only in the early years of the program. Chapter 7 concerning the observation of the core and inner core free nutations is paralleled by a twin paper (Dehant et al. 2005(Dehant et al. , A&A, 438, 1149) that proposes a theoretical development for their atmospheric and oceanic excitation.

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Section: Prograde Ficnsupporting

confidence: 82%

Section: Precession and Obliquity Ratementioning

confidence: 99%

Sidereal orientation of the Earth and stability of the VLBI celestial reference frame

Feissel-Vernier

Ma²,

Gontier

et al. 2005

A&A

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“…The artificial displacement of the sources towards the poles was already noticed in several earlier works (e.g., Ma et al 1998;Gontier et al 2001;Feissel-Vernier 2003). It can be physically understood as resulting from the dissymmetry of the network: during the first two decades of VLBI, most of the antennas (and most of the observed sources) were in the northern hemisphere.…”

Section: Systematicsmentioning

confidence: 57%

Comparison of VLBI radio source catalogs

Lambert

2014

A&A

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Aims. I checked the consistency of recent astrometric radio source catalogs obtained by geodetic very long baseline radio interferometry (VLBI) with the second realization of the International Celestial Reference Frame (ICRF2), released in 2009, which is the most accurate astrometric catalog currently available. Methods. The catalogs were compared to the ICRF2 in terms of radio source coordinates, global second-degree deformations, and error distribution. Results. All catalogs were found to be consistent with the ICRF2 within 20 μas. At high observational rates, the formal error is likely limited to the level of ∼10 μas by correlated-noise errors. The comparison of offsets to ICRF2 against formal errors raised noise floors of the differences between 50 μas and 100 μas, and hence no improvement with respect to the ICRF2. Conclusions. The inconsistencies between catalogs result in differences significantly larger than the accuracy expected for the future realizations of the celestial reference frame. These inconsistencies have to be clarified in the near future in view of the next ICRF realization and accurate linking to reference frames at other frequencies.

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“…The referencing of the session results to ITRF2000 includes a no-net-translation condition, the use of the corresponding EOP, and no adjustment in scale (Ma, personal communication). Results were used starting in 1990, when the operation of the VLBI network reached a first maturity stage (Gontier et al, 2001). …”

Section: Data Pedigreementioning

confidence: 99%

Stability of VLBI, SLR, DORIS, and GPS positioning

2007

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The residual signal in VLBI, SLR, DORIS and GPS station motion, after a linear trend and seasonal components have been removed, is analysed to investigate site-specific and technique-specific error spectra. The study concentrates on 60 sites with dense observation history by two or more space geodetic techniques. Statistical methods include the Allan variance analysis and the three-cornered hat algorithm. The stability of time-series is defined by two parameters, namely the Allan deviation for a one-year sampling time (noise level) and the slope of the Allan variance graph with its spectral interpretation (noise type). The site-specific noise level is found to be in the range 0.5-3.5 mm in either horizontal direction and 1-4.5 mm in height for most sites. The distribution of site-specific noise type includes both white noise and flicker noise. White noise is predominant in the East direction. Both types of noise are found in the North direction, with no particular geographical clustering. In the Up direction, the Northern hemisphere sites seem to be split in two large geographical sectors characterised either by white noise or by flicker noise signatures. Technique-specific noise characteristics are estimated in several ways, leading to a white noise diagnostic for VLBI and SLR in all three local directions. DORIS has also white noise in the horizontal directions, whereas GPS has a flicker noise spectrum. The vertical noise spectrum is indecisive for both DORIS and GPS. The three-dimensional noise levels for the one-year sampling time are 1.7 mm for VLBI, 2.5 mm for SLR, 5.2 mm for DORIS, and 4.1 mm for GPS. For GPS, the long-term analysis homogeneity has a strong influence. In the case of a test solution reanalysed in a fully consistent way, the noise level drops to the VLBI level in horizontal and to the SLR level in vertical. The three-dimensional noise level for a one-year sampling time decreases to 1.8 mm. In addition, the percentage of stations with flicker noise drops to only about 20% of the network.

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Stability of the extragalactic VLBI reference frame

Cited by 36 publications

References 8 publications

Sidereal orientation of the Earth and stability of the VLBI celestial reference frame

Sidereal orientation of the Earth and stability of the VLBI celestial reference frame

Comparison of VLBI radio source catalogs

Stability of VLBI, SLR, DORIS, and GPS positioning

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