Hubble Space Telescope allows us to study the central surface brightness profiles for globular clusters at unprecedented detail .
We have mined the \it { HST } archives to obtain 38 WFPC2 images of galactic globular clusters with adequate exposure times and filters , which we use to measure their central structure .
We outline a reliable method to obtain surface brightness profiles from integrated light that we test on an extensive set of simulated images .
Most clusters have central surface brightness about 0.5 mag brighter than previous measurements made from ground-based data , with the largest differences around 2 magnitudes .
Including the uncertainties in the slope estimates , the surface brightness slope distribution is consistent with half of the sample having flat cores and the remaining half showing a gradual decline from 0 to -0.8 ( dlog \Sigma / dlog r ) .
We deproject the surface brightness profiles in a non-parametric way to obtain luminosity density profiles .
The distribution of luminosity density logarithmic slopes show similar features with half of the sample between -0.4 and -1.8 .
These results are in contrast to our theoretical bias that the central regions of globular clusters are either isothermal ( i.e .
flat central profiles ) or very steep ( i.e .
luminosity density slope \sim - 1.6 ) for core-collapse clusters .
With only 50 % of our sample having central profiles consistent with isothermal cores , King models appear to poorly represent most globular clusters in their cores .