EDP Sciences
Free access
Issue A&A
Volume 493, Number 1, January I 2009
Page(s) 317 - 323
Section Celestial mechanics and astrometry
DOI http://dx.doi.org/10.1051/0004-6361:200810582
Published online 06 November 2008



A&A 493, 317-323 (2009)
DOI: 10.1051/0004-6361:200810582

On radio source selection to define a stable celestial frame

S. B. Lambert and A.-M. Gontier

Observatoire de Paris, Département Systèmes de Référence Temps Espace (SYRTE), CNRS/UMR8630, 75014 Paris, France
    e-mail: [sebastien.lambert;anne-marie.gontier]@obspm.fr

Received 12 July 2008 / Accepted 7 October 2008

Abstract
Context. The most accurate realization of a quasi inertial reference frame, the International Celestial Reference Frame (ICRF), is made of 212 defining extragalactic radio sources whose coordinates are determined using VLBI observations. Recent studies demonstrated however that using other sets of sources could improve the frame stability.
Aims. This study examines a simple radio source selection scheme to define celestial reference frame axes more stable than the ones as currently defined by the ICRF.
Methods. After having derived source coordinate time series from 26 years of VLBI observations, we select the most suitable sources on the basis of their positional variability (rms and slope), and observational history. We determine the axis stability of the frame defined by the selection, as well as its suitability for global geodetic VLBI analyses, i.e., determination of Earth orientation parameters and source and station coordinates.
Results. We select four frames made of 196, 200, 262, and 269 sources, respectively, showing a satisfactory sky coverage in both hemispheres. Our selections provide a frame stability improved by up to 40% with respect to the ICRF, and by 20% with respect to the frame as defined by the 247 stable sources of Feissel-Vernier et al. (2006, A&A, 452, 1107). Reanalysis of data with respect to this frame gives astrometric catalogues aligned to the ICRF-Ext.2 within 17 $\mu$as. Effects on the Earth orientation parameter estimates and terrestrial reference frame determination remain marginal.
Conclusions. In view of the generation of the next ICRF, we recommend that such an algorithm be taken into consideration along with other criteria based on individual characteristics of the radio sources.


Key words: reference systems -- Earth



© ESO 2008

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)