Recent tracking data suggested that the new race defect was of similar position and profile as that in 1997, but of smaller amplitude. The old empirical correction was thus resurrected and scaled to an amplitude at the horizon of 3.5". Uranus was then tracked with RxB and the fives method through (az,el) = (240,37) with the following results :

Both sets of residuals show linear negative trends through the hour-long exercise which have no impact on the matter at hand.

By comparison with the previous data the defect is largely corrected and may even be over-corrected by about 1" at both extremes.

Thanks to Jonathan for his efforts this morning to overcome the formatting errors in the file I created yesterday. I have updated the empirical correction adopting a smaller amplitude at the horizon (3.0"). This can be implemented after software startup - either in order to perform a second test or in order to provide what I think will be better tracking performance - by sending the following command

    icl> send pueo##THI set EMPIRICAL 1

It is disabled by

    icl> send pueo##THI set EMPIRICAL 0

A test of this new empirical correction file is desirable, but I am confident that observing with it enabled is better than observing with it disabled. We will iterate towards the right amplitude quickly, but the amplitude needs regular monitoring and a more resolved profile must wait for the return of SCUBA.