  A sub-parsec scale radio counterjet has been detected in the nucleus of the
closest radio galaxy, Centaurus A (NGC 5128), with VLBI imaging at 2.3 and 8.4
GHz. This is one of the first detections of a VLBI counterjet and provides new
constraints on the kinematics of the radio jets emerging from the nucleus of
Cen A. A bright, compact core is seen at 8.4 GHz, along with a jet extending
along P.A. 51 degrees. The core is completely absorbed at 2.3 GHz. Our images
show a much wider gap between the base of the main jet and the counterjet at
2.3 GHz than at 8.4 GHz and also that the core has an extraordinarily inverted
spectrum. These observations provide evidence that the innermost 0.4-0.8 pc of
the source is seen through a disk or torus of ionized gas which is opaque at
low frequencies due to free-free absorption.
