The International Celestial Reference Frame (ICRF) is currently defined by the radio positions of 212 extragalactic objects. Since its inception there have been two extensions to the ICRF. These extensions included revised positions of ICRF candidate and "other" sources, based on inclusion of additional observations, as well as positions of an additional 109 "new" sources. With continued applicable VLBI observations and improvements in analysis a better realization of the ICRF is now possible and an even better realization is feasible in the foreseeable future. Planning for a second realization of the ICRF is currently underway with a projected completion date concurrent with the XXVII^th IAU General Assembly in 2009. The work will be carried out by two working groups as listed below.

UPDATE: On 13 August 2009, the XXVII IAU General Assembly approved without dissent Resolution B3 adopting the ICRF2 as the fundamental celestial reference frame as of 1 January 2010. A complete description of ICRF2 is available in IERS Technical Note 35.