Pointing/Inclinometry meeting - report & actions

Present: RMP, IMC, DDC, RJSG

1. We reviewed RJSG's note about investigations into inclinometry data
(981124 on the web page). RMP had one minor query which I will address
offline.

2. We looked further at the data for spike size and general variability vs
time (981204 and 981208 on the web, plus extra plots from RJSG). The clear
conclusion is that the general variability is no worse now, than it was two
years ago. Spikes, however, are definitely on the rise. 

* ACTION RJSG to put my pictures on the web.

3. We looked at a detail analysis of the data for 980606, 980610, and
980611. One very odd feature of the data was explained by an error in the
way I had analysed the  data. Another difference between RJSG's and IMC's
plots was due to some deliberate massaging that had gone on. There remain
some very strange features in the 980610 data set which we conclude were
probably due to someone inadvertently going onto the antenna during the 
inclinometry run.

4. We discussed DDC's recent work and future plans. He has fitted
strain gauges with temperature-compensation bridges to the inside and
outside of the track, with home-built bridge completion modules that are
much less noisy than the commercial units. Next step will be to hook those
up to the DGH daisy-chain and then we will be able to routinely take data
on the wheel weights during inclinometry. DDC will also wire up the fourth
inclinometer so we can do regular inclinometry plus have an extra module
for tests such as the SY/LY test we have been doing. THis may require
purchase of new DGH modules at a cost of about $1000.

* ACTION DDC to continue wiring up units and look for spare DGH's
* ACTION RJSG to request new funding if no spare units are available.

5. IMC showed plots of SCUBA pointing vs time which showed that the
pointing is NOT getting worse (with SCUBA over the last two years,
anyway). This raises the question of whether our troubles can be traced to
the telescope rebalancing we did when SCUBA arrived?

NB - the fact that the mean pointing is not getting worse does not mean
there is no problem. The spikes introduce some nasty local variations in
pointing which ruin some kinds of science, and which sometime ruin almost
any science. And the spikes ARE getting worse.

* ACTION IMC to produce similar plots for RxA, going back to 1995-ish

5. We had a more general "brainstorming" around the "Assumptions,
Observations, Inferences" paper RJSG has been drafting. Various additions
and corrections.

* ACTION RJSG to update the paper, include an "unanswered questions"
section, and put on the web with help from IMC.
* ACTION RJSG to get the shim he has bought, put onto the track.
* ACTION RJSG to make a table of bad wheel/track interactions by looking
at the difference plots.
* ACTION RJSG to do simple sums on stiffnesses, deflections and forces.

6. We agreed that we would leave the spare inclinometer hooked up for now,
until we had seen some really nasty (5-6 sec) spikes.

That's about all for now.

Cheers - Justin.