Karine Le Bail

Karine Le Bail
Onsala Space Observatory / Chalmers University of Technology · Department of Space, Earth and Environment

PhD

About

50
Publications
2,407
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436
Citations
Additional affiliations
May 2009 - November 2016
Independent Researcher
Position
  • Researcher

Publications

Publications (50)
Article
The Continuous Very Long Baseline Interferometry (VLBI) Campaign 2017 (CONT17) was observed from November 28 to December 12, 2017 and featured three independent observing networks. Two legacy S/X networks of nominally 14 stations each observed in parallel for the full 15 days of the campaign. One of them was made possible in large part by the parti...
Poster
Full-text available
The K-band Celestial Reference Frame: First Imaging Results
Presentation
Full-text available
K-band Celestial Reference Frame
Presentation
Full-text available
Improving the S/X Celestial Reference Frame in the Southern Hemisphere
Article
Full-text available
Aims. We investigate the composition of the noise in coordinate time series of several hundreds of extragalactic radio sources moni- tored by the geodetic VLBI program since 1979. The noise type is identified at all available timescales longer than one year, following the observational history of the source. Methods. We computed the Allan standard...
Presentation
Full-text available
Preliminary results of an exploring project to collect astrophysical information about VLBI radio-sources and understand what distinguish stable sources and unstable sources
Article
The International Celestial Reference Frame suffers from significantly less observations in the southern hemisphere compared to the northern one. One reason for this is the historically low number of very long baseline interferometry radio telescopes in the south. The AuScope very long baseline interferometry array with three new telescopes on the...
Article
Full-text available
The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency's Gaia mission, launched on 2013 Dec...
Article
Full-text available
The NASA GSFC DORIS analysis center has processed data from January 1993 to December 2014 and provided 1141 weekly solutions in the form of normal equations for incorporation into the DORIS solution for ITRF2014. The solution time series, designated as gscwd26, were based on tracking data to eleven DORIS satellites divided generally into seven-day...
Data
Very Long Baseline Interferometry (VLBI) is a primary space-geodetic technique for determining precise coordinates on the Earth, for monitoring the variable Earth rotation and orientation with highest precision, and for deriving many other parameters of the Earth system. The International VLBI Service for Geodesy and Astrometry (IVS, http://ivscc.g...
Article
The construction of the second realization of the International Celestial Reference Frame by VLBI (ICRF2) was undertaken to take advantage of the many improvements in geodetic and astrometric VLBI and the vast increase in data since the first ICRF. The impact the switch to ICRF2 has had on the terrestrial reference frame and EOP solutions generated...
Article
Variations in the temporal length-of-day (LOD) contain information on phenomena related to the continuous evolution of Earth processes: tidal energy dissipation and core-mantle coupling (decadal, secular), meteorological and solar-lunar tide effects (annual, semiannual). In this work, we studied an LOD time series obtained from VLBI measurements an...
Article
IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We compared the IGN and DGFI TRFs with a GSFC CALC/SOLVE TRF. WRMS position and velocity differences for the 40 most frequently observed sites were 2-3 mm and 0.3-0.4 mm/year. There was a scale...
Article
The time-variations in the gravity field have been shown to show the secular signature of post glacial rebound, and evidence of mass transport in the Earth system on annual and monthly and sub-monthly time scales. While the GRACE data provide a detailed view of the variations in the geopotential over the past ten years, space geodetic tracking data...
Article
The ICRF2 became official on Jan 1, 2010. It includes positions of 3414 compact radio astronomical sources observed with VLBI, a fivefold increase over the first ICRF. ICRF2 was aligned with the ICRS using 138 stable sources common to both ICRF2 and ICRFExt2. Maintenance of ICRF2 is to be made using 295 defining sources chosen for their historical...
Article
The Singular Spectrum Analysis (SSA) is a method widely use, especially in climatology. Its purpose is to spectrally decompose time series at different levels of frequency. This tool is applied to VLBI geodetic data in this study. But the challenge with VLBI time series is the lack of regularity: the observations are not done continuously, leading...
Article
For the development of ITRF2008, the International DORIS Service (IDS) for the first time developed a combination based on the contributions of seven analysis centers using five separate software packages. Data from 1993 to 2009 were processed in weekly batches using the latest geodetic processing standards, mostly consistent with the IERS standard...
Article
Atmospheric water vapor is one of the largest contributors to the error budget for modeling signal time propagation in radio technique observations. In order to validate the tropospheric parameters estimated from VLBI data analysis, we compared the estimates with co-located WVR measurements and GPS estimates of total zenith delay. We analyzed the V...
Article
GRACE has been routinely monitoring the time-variable gravity field of the Earth since 2003 with either periodic solutions expressed as spherical harmonics or mascons. GRACE can resolve time-variable gravity to between degree 40 and 60, however the time series may be interrupted prior to the launch of a GRACE-2 spacecraft. A suite of satellites tra...
Article
In VLBI analysis, atmospheric delay is modeled as two parts: the hydrostatic or dry delay, which it is assumed can be calculated from local meteorological data, and a wet delay which must be estimated. Errors in calibrating and estimating the atmosphere are one the dominant error sources in VLBI and other space-geodetic techniques. In this presenta...
Article
Temporal statistical position stability is required for VLBI sources to define a stable Celestial Reference Frame (CRF) and has been studied in many recent papers. This study analyzes the sources from the latest realization of the International Celestial Reference Frame (ICRF2) with the Allan variance, in addition to taking into account the apparen...
Article
The NASA GSFC DORIS analysis center has provided weekly DORIS solutions from November 1992 to January 2009 (839 SINEX files) of station positions and Earth Orientation Parameters for inclusion in the DORIS contribution to ITRF2008. The NASA GSFC GEODYN orbit determination software was used to process the orbits and produce the normal equations. The...
Article
For the development of the new realization of the terrestrial reference frame, ITRF2008, the Goddard Space Flight Center reprocessed the DORIS data from six satellites (TOPEX/Poseidon, SPOT-2, SPOT-3, Envisat, SPOT-4 and SPOT-5) from 1992 to 2008. The reprocessing followed the modeling standards and analysis strategies recommended by the Internatio...
Article
The International DORIS Service (IDS), in operation since 2003, submitted three sets of solutions to ITRF2005 from the IGN/JPL, LEGOS/CLS, and INASAN analysis centers, but no DORIS technique combination. Since that time new analysis centers have become operational including the Geodetic Observatory Pecny (GOP), the European Space Operations Center...
Article
The International DORIS Service (IDS), in operation since 2003, submitted three sets of solutions to ITRF2005 from the IGN/JPL, LEGOS/CLS, and INASAN analysis centers, but no DORIS technique combination. Since that time new analysis centers, have become operational, including the Geodetic Observatory Pecny (GOP), and the European Space Operations C...
Article
The GRACE gravity mission has now supplied us with solutions for the time variations in the Earth's gravity field that now span more than five years, from 2003 to the present. Solutions are available from different analysis centers: GSFC, CNES, JPL, and UT/CSR. Satellite laser ranging (SLR) and DORIS (Doppler Orbitography and Radiopositioning) Inte...
Article
Surface mass redistribution within the Earth system, especially in the atmosphere, oceans, continents and ice sheets, causes the position of the Earth's center of mass (geocentre) to vary in a reference frame attached to the solid Earth. Space techniques as the Doppler Orbitography and Radiopositioning Integrated on Satellite (DORIS) and the Satell...
Article
The International DORIS Service is in operation since 2003. Over the last four years, five instruments on the SPOT 2-4-5, ENVISAT and the JASON-1 satellites have provided DORIS Doppler data collected from a global network of about 50 stations. The number of Analysis Centers (AC) who have processed the data and have high level experience has progres...
Article
The Lageos-1 (L1) and Lageos-2 (L2) satellites have formed the basis of the ILRS contribution to the ITRF2005. These geodetic cannonball satellites, launched in 1976, and 1992 respectively are well suited for this purpose, by virtue of their high altitude, and lack of sensitivity to either high degree gravity terms or the deleterious effects of atm...
Article
Full-text available
The residual signal in VLBI, SLR, DORIS and GPS station motion, after a linear trend and seasonal compo-nents 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 Al...
Chapter
Analysing time series of space-geodetic station coordinates, we show that VLBI, SLR and DORIS station motions have a white noise error spectrum, while the majority of GPS station motion have a flicker noise error spectrum. In the latter case, discontinuities in the series do not account for this spectrum. Atmospheric loading has a white noise spect...
Article
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 technique-specific error spectra. The study concentrates on 60 sites with dense observation history by two or more space geodetic techniques. Statistical methods used include Allan variance analysi...
Article
In a cooperation between the Astronomical Institute, University of Bern (AIUB), the Geodetic Observatory Pecný (GOPE), and the Institut Géographique National (IGN), DORIS data analysis capabilities were implemented into a development version of the Bernese GPS software. The DORIS Doppler observables are reformulated such that they are similar to gl...
Article
The noise spectrum in DORIS ground- station motion is investigated by means of the Allan variance method applied to the decomposition of the 3D signal into its principal components in the time domain. Sets of weekly position time-series from 1994 to 2005 derived by three IDS Analysis Centres (IGN-JPL, INASAN, and LEGOS-CLS) for 119 stations at 69 s...
Article
Full-text available
All space-geodetic techniques are now organized as separate services of the International Association of Geodesy (IAG), supporting the first pilot project “Global Geodetic Observing System (GGOS)”. The International DORIS (Détermination d’Orbite et Radiopositionnement Intégrés par Satellite) Service (IDS) was created in mid-2003 to organize a DORIS...
Article
Geocentre motion signals measured by satellite geodesy and those predicted from the observed mass redistribution in the ocean, atmosphere and terrestrial waters over 1993.1–2003.0 are analysed and compared under two viewpoints: the amplitudes and phases of the seasonal components, and the spectral signature of the non-seasonal components. The geode...
Article
Journal of Geodesy, v. 80, n. 8-11, p. 637-648, 2006. http://dx.doi.org/10.1007/s00190-006-0079-z
Article
The accuracy of the Earth's geocenter motion estimates is one of the challenges of the global analysis of geodetic satellite measurements. The geocenter motions are ascribed to time varying mass distribution in the atmosphere, the oceans and ground waters. The motion of the Earth's center of mass (geocenter) with respect to a terrestrial reference...
Article
The background of this research is the use of time series of space geodetic station coordinates to study global or local tectonic motions, a research field currently in rapid development in geodesy. Time series of station coordinates are available from several global space geodetic programs operated with GPS, SLR, and DORIS. Good quality series go...
Article
Time-variations of the location of the geocenter relative to the Earth's crust are measured since the early 1990's by precise satellite positioning techniques (SLR, DORIS, GPS). On the other hand, redistributions of mass inside the Earth's system are expected to give rise to such motions. We computed time-series of hydrological contributions to the...
Article
The parallel operation of permanent space geodetic stations in colocation sites is a key aspect for meeting the goal of a fully integrated observing system. Taking the case of about 25 DORIS-GPS colocation sites where time series of coordinates are available from both techniques, we investigate the time behaviour of the station positions and study...
Article
Full-text available
The qualification and the maintenance of the International Celestial Reference Frame (ICRF) source directions are currently based on global statistics regarding the complete data set of VLBI observations of extragalactic radio sources. The founding hypothesis in the selection of extragalactic objects to access a quasi-inertial reference system is t...
Article
The file table 2 gives the results of various tests and noise measurements performed on time serie of extragalactic radio source coordinates. Systematic and random behaviours in time serie of individual determinations of cooordinates for 283 sources over 1987-1999 are investigated. The random variability of the source coordinates is characterized b...
Article
The founding hypothesis in the selection of extragalactic objects for accessing a quasi-inertial reference system is that their directions are fixed in space. Therefore the study of the time variability of the sources is an important step in the process for checking and improving the reliability of the ICRF. The systematic and random behaviours in...
Article
The motion of the Earth's center of mass (geocenter) with respect to a terrestrial reference frame attached to the crust is usually described by time series of the coordinates of the origin of the individual data sets derived from SLR, DORIS or GPS. On the other hand, global atmospheric and oceanic dynamics can be used to predict such motions. We c...

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