Vibrations in the SMU have been reported ( [20061215.006] & [20070119.002]). Vibration amplitudes are recorded in /jac_logs/UTdate/SMU_param.log and a script (/local/progs/bin/smustats) is available to plot them.

An example is shown below, illustrating some frequently seen features:

The raw data show vibration amplitudes of about 100units when displayed here as 2arcsecs - so the scale is about 50units/arcsec. The 'zero' of these traces is often, therefore, 0.04", often a couple of tenths of an arcsec. Features of note in many data include:

• NS amplitudes seem invariably about 1/10th the EW amplitudes.
• 'Spikes', of amplitude 1" or 0.5" (we shall talk almost exclusively hereafter about the EW data). These sometimes show periodicity. However, examination of the raw data reveals that they coincide with and result from the opening of each new observation file, and that their periodicity results from a rhythm in the observing : they are therefore spurious.
• The 'triangular ramp' (at UT18-20) results from a gap in the record, with the join-the-dots convention adopted in the plotting package generating the false impression of a 'ramp'.
• The longer-lasting, 2"-amplitude events are real, and usually have matching excursions in the NS axis, although of 1/10th amplitude.
• The phenomenon is not unambiguously associated with any one obstype.

The EW events are tabulated below as amplitude and UTs. Images of nightly data are available by clicking on the UT date, and these images are also available all together. A table of the observations that may be affected is updated every 10days or so and is available here.