Inclinometry was done as follows :

    Datasets  El Dirn     HST     mean leg temperatures   Humidity
                          start     start   middle   end       %
  ( 20051208  89  cw      03:48      2.4      2.4    2.4     100 )
    20060129  89  cw      19:40      5.1      5.1    5.0      22

All inclinometry and temperature data channels look; Ch13 - the #1 strain gauge - is still not functional.

The difference between the CW model resulting from these new data and the previous one of 08 Dec is shown below:

There is small amplitude (1") high-frequency ripple throughout. I present a Fourier analysis of the data - and what it might mean - below.

• The differences are v.small and (F1,F2,F3) are described by rms scatters of (0.39", 0.25", 0.30") c.f. (0.34", 0.51", 0.63") previously.

• The new CW model was merged with the (CW-CCW) template to create a hybrid track model, which was installed at HST 10:45 on 30 January 2006.

• The symmetry (defined here) remains fine, and the wheel loads remain somewhat elevated.

20060203
Part of the F3 data-difference in this most recent model-difference datastream is shown below-right, while that from a definitive occurrence in Sep 2000 is shown below-left:

The 8.8 degree 'ripple' is obvious in the 'definitive' data, though it's not nearly so obvious in the new data when the data is seen at this scale; the initial view of the data is, in this sense, a little misleading. Not surprisingly, therefore, Fourier analysis of this new difference shows less power than before:

(The larger peak is at a wavelength of 8.8 degrees, the smaller one an alias of 4.4).

The conclusions of the analysis of 03 Oct 2000 probably still hold in general:

"At this time it is assumed that there is no imminent danger of a catastrophic failure of the az-drive, similar to the 1992 event. The inclinometry data perturbations are most probably sign of either slippage of the roller due to misalignment, shaft bent due to the temporary overload during the center bearing adjustments, roller surface deformation (out of round) or the bearing wear. Magnitude of the perturbations is well below levels observed on average during last 1000 days."

Assuming a central bearing load adjustment is scheduled as part of the recovery of JCMT following the shutdown - a process that will either again effect a wheel realignment and/or produce new, benign alignments - there is probably nothing further to worry about.