A1 – Commission A1 Astrometry


The Commission A1 'Astrometry' coordinates research related to the celestial coordinate system (definition, realization, and maintenance) as well as positions, proper motions and parallaxes (distances) of celestial objects. It is also involved in the accurate determination of distances which is one of the most fundamental and important tasks of astrometry, forming the basis for astrophysical science.

Moreover the Commission A1 coordinates ground and space-based observing astrometric programs, and promotes education in astrometry. It spans a vast range of objects from the Earth-Moon system to quasars at cosmological distances, as well as a large range of techniques with the common goal of enhancing our understanding of motions of celestial objects and their measurement in coordinate systems.

Over the coming years Commission A1 will focus on supporting the following particularly important activities:

  • The construction of the ICRF3, the next version of the radio VLBI-based reference frame, which is the realization of the celestial coordinate system.
  • The ESA Gaia space mission, launched in Dec 2013, which will provide the next generation optical celestial reference frame. In particular Commission A1 will support the coordination of research to provide a solid link of this last frame to the ICRF3
  • The support of space and ground-based programs at various wavelengths, like LSST and others to densify the celestial coordinate system toward fainter magnitudes (fluxes). An important task will be to observe motions of targets fainter than those included in the primary frames (ICRF3, Gaia) or to observe any celestial object at various epochs.
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    Commission Members (209)

    Under Division

    Division A Fundamental Astronomy

    Jean Souchay

    Observatoire de Paris
    61 Av de l'Observatoire
    75014 Paris

    Phone: +33 1 40 51 23 22
    Fax: +33 1 40 51 22 91
    Email: jeansouchayobspmfr
    Organization website: http://syrte.obspm.fr/

    NCA adherence: France

    Last updated:
    December 6, 2017

    Christopher S. Jacobs

    Jet Propulsion Laboratory, Caltech
    Tracking and Applications Section
    Mail Stop 67-225
    4800 Oak Grove Dr.
    Pasadena 91109
    California (CA)
    United States

    Phone: +1 (818)354-7490
    Email: ChristopherSJacobsjplnasagov
    Personal website: https://www.iau.org/administration/membership/individual/15141/
    Organization website: http://www.jpl.nasa.gov/

    NCA adherence: United States

    Last updated:
    March 6, 2018

    Anthony G.A. Brown

    Leiden University
    Leiden Observatory
    PO Box 9513
    2300 RA Leiden

    Phone: +31 71 527 58 84
    Email: brownstrwleidenunivnl
    Personal website: http://www.strw.leidenuniv.nl/~brown
    Organization website: http://www.strw.leidenuniv.nl/

    NCA adherence: Netherlands

    Last updated:
    November 9, 2018

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