A3 – Commission A3 Fundamental Standards


The purpose of IAU Commission C.A3 - Fundamental Standards is to facilitate advances in astronomy, and other fields in science an engineering, by developing, implementing, and communicating fundamental IAU-endorsed standards for fundamental astronomy. Such standards include, but are not limited to:

  • celestial & terrestrial reference systems/frames and the transformations among them;
  • time scales;
  • precession-nutation models;
  • Earth rotation and polar motion, including physical models (e.g., Earth's gravity field, lunar gravity field, Earth interior model, solid Earth-tide modelling); star catalogues; ephemerides of solar system bodies; special and general relativistic models for time and space.

This involves:

  1. producing robust standards, and ensuring that new standards are readily understood by both the astronomical and broader scientific communities; i.e., are relevant and "fit for purpose";
  2. ensuring that the associated nomenclature is well defined and understood; encouraging future research, particularly groups with the appropriate expertise, to improve their models and help them to develop relevant standards;
  3. implementing good practices in setting and using IAU standards, including identifying requirements for new standards; providing a link between the users of fundamental standards and developers to (1) inform users of current standards and the status of those under development, and (2) to accept input from the broader user community in order to ensure that standards are relevant for practical needs; and
  4. encouraging interest among young astronomers in developing the field of astronomical standards and services for the scientific community.

FS will serve as the primary point of contact between Division A and the user community regarding standards for fundamental astronomy.

Join FS & help make standards easy for everyone.

Send comments, questions, suggestions to the President of Commission A3.

Work for the next 6 - 9 years:

  1. Maintain and enhance existing links between the IAU, the IERS, the IAG's GGOS, CCTF, and others;
  2. coordinate and promote the continued good work of SOFA, the WGNSFA, and the WGCCRE;
  3. develop, implement, and disseminate new standards currently under consideration and development within Div. A; e.g., ICRS3, precession-nutation models, and relativistic VLBI standards;
  4. develop a Web presence for communication and coordination that will both inform users about status of new and emerging standards, and provide a means for the user community to provide feedback on standards;
  5. ensure that user feedback on fundamental standards is shared with scientists who are developing new standards within the IAU framework; actively develop new and improved standards and services to meet emerging needs;
  6. promote and encourage interest among young astronomers in developing the field of astronomical standards and services for the scientific community.


Here is the External site Link (including the list of Numerical Standards for Fundamental Astronomy). 


Commission Web Page

Commission Members (103)

Under Division

Division A Fundamental Astronomy

Susan Gessner Stewart

United States Naval Observatory
Astronomical Applications
3450 Massachusetts Ave., NW
Washington 20392-5420
United States

NCA adherence: United States

Last updated:
March 7, 2022

Jose Manuel Ferrándiz

Universidad de Alicante
Depto de Matematica Aplicada
Escuela Politécnica Superior
Campus de San Vicente. PO Box 99
03080 Alicante

NCA adherence: Spain

Last updated:
March 5, 2021

James Lindsay Hilton

US Naval Observatory
Astronomical Applications Dept
1274 Hwy 238
Jacksonville OR 97530
Oregon (OR)
United States

NCA adherence: United States

Last updated:
November 15, 2021

Organizing Committee

Search Scientific Bodies


Donate to the IAU

Donate to the IAU

IAU Strategic Plan 2020–2030

Strategic Plan

IAU Code of Conduct

Code of Conduct

Symposia and Meetings



How to Become a Member

Deceased Members

Deceased Members

Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference


IAU Catalyst

Latest Catalyst

IAU e-Newsletter
Volume 2022 n° 10

Latest e-Newsletter

Subscribe to the e-Newsletter


IAU Office of Astronomy for Development

Office for Astronomy Development

IAU Office for Young Astronomers

Office for Young Astronomers

IAU Office for Astronomy Outreach

Office for Astronomy Outreach

IAU Office of Astronomy for Education

Office of Astronomy for Education

International School for Young Astronomers

International School for Young Astronomers

WG Small Bodies Nomenclature Bulletins

WG Small Bodies Nomenclature Bulletins

IAU WG Women in Astronomy Newsletters and Ensemble Magazine

WG Women in Astronomy Newsletters