At the 2006 General Assembly of the International Astronomical Union (IAU), a proposal was adopted to form the Working Group (WG) for Numerical Standards of Fundamental Astronomy (NSFA). The goal of the WG is to update the “IAU Current Best Estimates" conforming with IAU Resolutions, the International Earth Rotation and Reference Systems Service (IERS) Conventions, and the Système International d'Unités (SI). The need for changes to the numerical standards are due mainly to the adoption of a new precession model, the redefinition of Barycentric Dynamical Time (TDB), and the significant improvement of the accuracy of recent estimates for a number of constants. The work from the first triennium culminated in the acceptance at the 2009 IAU General Assembly of Resolution B2 which adopted the NSFA list of Current Best Estimates as the IAU (2009) System of Astronomical Constants.