On UT 20050729, the empirical correction for the central bearing race defect was disabled and Uranus was tracked using RxB and the fives method. Tracking started at HST 04:50 at (az,el) = (231,47) and ended at HST 06:15 at (246,30). The pointing residuals are shown below:

The formal rms of the residuals in elevation is an impressive 0.4", while that in azimuth is 1.4". This latter is dominated by an unexplained secular decrease throughout the dataset, and includes the excursions due to the defect, which is clearly seen at azimuth 240 as expected.

The plot also shows (in green) the current empirical correction - constructed using an amplitude at the horizon of 3" - superimposed on the data. Allowing for the baseline offsets on either side of the defect there is again no apparent need to adjust the empirical correction at this time.