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990512 report

Inclinometry following addition of 3t of weights to the front of the antenna

SUMMARY
The new data show only minor changes from data taken prior to the loading, but reveal a possible loss of symmetry during CCW motions. 

   Datasets     HST start      mean leg temperatures   Humidity
                               start   middle   end       %
 ( inc990508      17:23         n/a     n/a     n/a      20 )
   inc990511cw    17:51         9.4     9.2     8.5      30
   inc990511ccw   21:19         8.5     7.6     5.5      35
   inc990512cw    00:22         5.5     4.4     3.8      40

The differences between the clockwise models 990512cw-990511cw and 990512(cw)-990508 are shown below :

  • The first CW run (990511cw) contains a few odd spikes, so we use the second CW run (990512cw) to generate the new track model.
  • The rms scatters in the (F1,F2,F3) differences are (0.57", 0.34", 0.42") and (0.30", 0.12", 0.39"), respectively.
  • The new track model was installed at 17:00 HST on 19990512.

Symmetry
The symmetry remains good (see the plot ).

However, this symmetry plot is based exclusively upon clockwise (CW) data. The CCW data is also amenable to this same analysis and provides a surprise : 

      dataset       scatter about the best-fit str line to
                    Ch2 -vs- Ch8   Ch5(phase-flipped) -vs- Ch8
               i.e.  TY -vs- RY     LY(phase-flipped) -vs- RY
    ------------     ----------     -------------------------
    inc990511cw         0.73"                 1.41"
    inc990511ccw        1.05                  1.87
    inc990512cw         0.72                  1.56
i.e. the antenna 'loses its symmetry' going CCW. (The significance of the ccw values must be judged against the plot ). The relevant data from 971031 and 980820 are given below : 

      dataset       scatter about the best-fit str line to
                    Ch2 -vs- Ch8   Ch5(phase-flipped) -vs- Ch8
               i.e.  TY -vs- RY     LY(phase-flipped) -vs- RY
    ------------     ----------     -------------------------
    inc971031cw         0.59"                 1.56"
    inc971031ccw        0.79                  2.37
    inc980820cw         0.76                  4.30
    inc980820ccw        0.74                  4.98
The latter data are from a period of great instability - so are probably of less value - although the TY -vs- RY data show no cw-ccw bias. On the other hand the 971031 data tend to support the above claim that the CCW motion is inherently less symmetric .
More data please.

CW-CCW
The cw-ccw data are shown below :

The differences in (F2,F3) are small : rms scatters of (0.21", 0.39"), and the difference in F1 is similar to that seen on 980820 . The cw-ccw difference in F1 was suggested at that time to be 'evolving' : we update the plot as shown below :

The amplitudes on the scale of the track segments seems relatively unchanged since 980820, but the overall amplitude now (6") is more like that at 971031 rather than at 980820 (9").

Iain Coulson
13 May 1999
Contact: Iain Coulson. Updated: Sat Nov 6 18:00:31 HST 2004

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