FS banner

Information on Various Standards

This is a collection of links to various International Astronomical Union (IAU) recommendations and standards. The links with the abbreviated names, on the left, takes you to the web site of the group or report, the name of which is given in full in bold in the right paragraph. This list does not claim to be complete.


Resolutions Resolutions adopted at the General Assemblies
This IAU web page lists each GA and a file that may be downloaded that contains the text of the resolutions that were passed.
2000-2021 Summary: Reference Systems Our summary of the IAU and International Union of Geodesy and Geophysics (IUGG) resolutions that relate to reference systems, and in particular those after the IAU 1997 adoption of the International Celestial Reference System and Frame (ICRS/ICRF).
SOFA Standards Of Fundamental Astronomy (SOFA)
The IAU's SOFA service has the task of establishing and maintaining an accessible and authoritative set of algorithms and procedures that implement in software standard models used in fundamental astronomy. The service is managed by an international panel, the SOFA Board, appointed through IAU Division A - Fundamental Astronomy. SOFA also works closely with the International Earth Rotation and Reference Systems Service (IERS).
WG NSFA Working Group for Numerical Standards for Fundamental Astronomy
Commission A3 has assumed the role of maintenance for the IAU system of astronomical constants (2009/2012) and a list of Current Best Estimates formulted by the former IAU WG NSFA.
WG CCRE Working Group for Cartographic Coordinates and Rotational Elements
This IAU Division A/F WG has the responsibility to define the rotational elements of the planets, satellites, asteroids, and comets of the solar system on a systematic basis and to relate their cartographic coordinates rigorously to the rotational elements.
ICRF3 The Third Realization of the International Celestial Reference Frame by Very Long Baseline Interferometry (VLBI)
This third realization of the ICRF was adopted by the IAU in August 2018 and replaced the previous realization, ICRF2, on January 1, 2019. The ICRF3 includes positions of a total of 4588 sources across three radio-frequency bands. There are 303 "defining" sources which are uniformly distributed and serve to define the axes of the frame. The IAU Division A WG for the ICRF3 provided a recently published manuscript describing the ICRF3.
WG NFA Working Group on Nomenclature for Fundamental Astronomy
This IAU Division 1 WG (2003-2006) produced a glossary of terms and a process chart illustrating the transformation from the ICRS to the observed places of stars. The IAU recommendations on nomenclature relating to the IAU 2000/2006 resolutions concerning fundamental reference systems were published in the Transactions of the IAU, Volume XXVIB.
Nominal Units WGFormer Working Group on Nominal Units for Stellar and Planetary Astronomy
The work of this IAU Inter-division (A-G) WG resulted in two resolutions. See IAU 2015 Resolutions; alternatively the arXiv.org links below publish full details of both resolutions:
Resolution B2 for the recommended zero points for the absolute and apparent bolometric magnitude scales, and
Resolution B3 for the recommended nominal conversion constants for selected solar and planetary properties.
IAG GGOSThe Global Geodetic Observing System (GGOS) Bureau of Products and Standards (BPS)
A major goal of the International Association of Geodesy's (IAG) GGOS BPS is to coordinate the establishment and maintenance of unique standards for the processing of geodetic observations for geometric and for gravimetric techniques within GGOS and IAG. The geodetic standards include, i.e., physical units and constants, mathematical-physical models for geodetic observations and reduction models. Various standards have been defined for specific geodetic fields (e.g., IAG Resolutions, IERS Conventions) which form the basis for the work of the BPS. This reference work, Inventory of Standards and Conventions used for the Generation of IAG Products is included in The Geodesist's Handbook 2016 (pages 907-1205), an open access article in the Journal of Geodesy (October 2016, 90, Issue 10).
SI Units
and the   Astronomical System
of Units
The international system (SI) of units, prefixes, and symbols should be used for all physical quantities except that certain special units (see the SI brochure on the Bureau International des Poids et Mesures (BIPM) web site for details) may be used in astronomy, without risk of confusion or ambiguity, in order to provide a better representation of the phenomena concerned.
It is convenient for astronomers to use, for certain applications, an astronomical system of units, in which the unit of mass is equal to the mass of the Sun, MS, the unit of time is one day, D, and the unit of length is the astronomical unit of length (or simply the "astronomical unit").
Note that the astronomical unit (au) was re-defined in Resolution B2 of the 2012 IAU GA, so that: 1 au = 149 597 870 700 m. This unit is listed in Table 6 of the SI Brochure: The International System of Units (SI) (8th edition, updated 2014.)
Ephemeris Access Report of the IAU Commission 4 Working Group on Standardizing Access to Ephemerides and File Format Specification
An IAU Commission 4 WG (2010-2015) recommended a standard format for ephemerides. This format uses the widely used SP and PC kernels (designated SPK and PCK, respectively), slightly modified to meet the needs of all the current, widely available, high accuracy planetary ephemerides. Provision has also been made to allow for future innovation with backward compatibility. The software packages CALCEPH and SPICE support this format, so users can have confidence that these packages will be able to read any of these ephemerides. [This in no way invalidates software written by any group for reading a particular ephemeris.]
IAU Style Manual The IAU Style Manual - a 4.7MB PDF file, by G.A. Wilkins, for Commmission 5, published in chapter 8 of the Transactions of the IAU XXB (1989).
The IAU Rules, Guidelines and Instructions for Proceedings has additional information, such as LaTeX templates and Abbreviations in references to Serial Publications.
Last modified: 2020 April