Extending the very long baseline interferometry celestial reference frame to the Southern Hemisphere

Geodetic very long baseline interferometry measurements have been extended to the southern hemisphere using stations in South Africa, Tasmania, and Chile. These measurements enabled us to add a number of southern hemisphere radio sources to the catalog that defines our celestial reference frame. Positions have been determined for 81 radio sources ranging in declination from 78° N to 80° S with formal errors of a few tenths of a millisecond of arc. Numerical experiments to determine the sensitivity of the estimated positions to systematic error sources such as atmospheric refraction variations indicate that they are roughly comparable in magnitude to the formal errors. Preliminary measurements of the total and correlated source flux densities at 2.3 and 8.4 GHz are presented for a subset of the sources in the southern hemisphere.