The first test of the corrected TCS algorithm was performed by tracking irc+10216 for an hour through transit. The observed pointing residuals are shown as a function of azimuth:

The raw rms scatters in (daz,del) are (1.0", 1.9"). There is no independent assessment of seeing at this time. Apart from a 3" excursion at az=199, the azimuth residuals seem normally distributed. Azimuth=199 might just correspond to a track joint involving wheel 1 and track joint 13/14, but overall the data reflect an improvement over the 5" excursions seen at several places in the same azimuth range using the 'erroneous' TCS recently and more recently.

The elevation residuals show a 5" rise across transit that certainly mimics the (uncorrected) 'transit' effect. However, our understanding of this effect is that it achieves an (uncorrected) maximum at the horizon and diminshes to zero at higher elevations. The observed behaviour would then suggest an outstanding corrected effect at the horizon of ~40", so for now we might consider this likeness to be coincidental, although it should not be ignored. One wonders if reported problems with the weather station / noticeboard at this time had any effect ?

A repeat of this experiment would reveal the reality of the excursion at az=199 in daz and the 'transit' step in del, and a similar experiment in the north would test the benificence of the new hybrid track model.

20030419
A repeat was done the next night:

The azimuth residuals do not now show the 'feature' seen last night at az=199, nor any of the excursions seen in the data prior to the correction to the TCS. The raw rms scatter in daz for this hour's worth of data is 0.9". I feel that these two results justify the correction to the TCS algorithm, and quantify the resultant improvement.

The elevation residuals again mimic the 'transit' effect. The three tracking experiments of 20030318 also exhibit a 5" step in the elevation residuals through transit for irc+10216 (which transits at 83 degrees), a 2" step for 3c279 (64degs) and no detectable step in the Mars data (47degs). This is not the trend expected from the 'transit' effect, but the reality and functional form of this effect cannot be denied. Again it resembles a possible error in our assumed functional form for the effect.

The investigation continues.