The Galileo probe deceleration module contained an experiment which measured the recession of the forebody heat shield during the ablative probe entry into the Jovian atmosphere. A detailed description of the experiment, reduction of the probe data, reconstruction of the heat-shield shape, and comparisons with preflight predictions are presented. Data quality is good during the second half of recession, but excessive noise levels at the onset of ablation prevented the experiment from meeting two of three performance requirements. The recession distribution is surprisingly dissimilar from preflight predictions. Measured recession was less than predicted near the stagnation point, but exceeded predictions over most of the frustum. (Author)