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The International VLBI Service for Geodesy & Astrometry (IVS) regularlyprovides high-quality data to produce Earth Orientation Parameters (EOP), andfor the maintenance and realization of the International Terrestrial andCelestial Reference Frames, ITRF and ICRF. The first iteration of the celestialreference frame (CRF) at radio wavelengths, the ICRF1, was adopted by theInternational Astronomical Union (IAU) in 1997 to replace the FK5 opticalframe. Soon after, the IVS began official operations and in 2009 there was asignificant increase in data sufficient to warrant a second iteration of theCRF, ICRF2. The most recent ICRF3, was adopted by the IAU in 2018. However, dueto the geographic distribution of observing stations being concentrated in theNorthern hemisphere, CRFs are generally weaker in the South due to there beingfewer Southern Hemisphere observations. To increase the Southern Hemisphereobservations, and the density, precision of the sources, a series of deep Southobserving sessions was initiated in 1995. This initiative in 2004 became theIVS Celestial Reference Frame Deep South (IVS-CRDS) observing program. Thispaper covers the evolution of the CRDS observing program for the period 1995 to2021, details the data products and results, and concludes with a summary ofupcoming improvements to this ongoing project.

On More than Two Decades of Celestial Reference Frame VLBI Observations in the Deep South: IVS-CRDS (1995-2021)