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.

Commission Web Page

Commission Members (206)

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:
April 16, 2020

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:
October 8, 2020

Aletha de Witt

Hartebeesthoek Radio Astronomy Observatory,
Fundamental Astronomy
P.O. Box 443
1740 Krugersdorp
South Africa

Phone: +27 0123013222
Email 1: alethartraoacza
Email 2: alethahartraoacza
Organization website: http://www.hartrao.ac.za

NCA adherence: South Africa

Last updated:
April 16, 2020

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:
February 26, 2019

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