  We have measured the physical properties of polar coronal holes from the
minimum activity phase of solar cycle 23 (1996-1997) to the present minimum of
solar cycle 24 (2007-2009) using the UVCS instrument on SOHO. Observations in H
I Lyman alpha (121.6 nm) and O VI (103.2, 103.7 nm) provide spectroscopic
diagnostics of proton and O5+ bulk outflow velocities and velocity
distributions as a function of heliocentric distance above the poles of the
Sun. These observations have allowed us to follow the changes in the physical
properties of the polar coronal holes during solar cycle 23 and its approach to
the current minimum. Recent ground- and space-based observations have reported
a variety of phenomena associated with the current minimum. We present the
comparison of observed oxygen line intensities, line ratios, and profiles for
polar coronal holes at both minima and during solar cycle 23 and show how this
new minimum manifests itself in the ultraviolet corona. The comparison of the
physical properties of these two minima as seen by UVCS in the extended corona,
now possible for the first time, may provide crucial empirical constraints on
models of extended coronal heating and acceleration for the fast solar wind.
