New track model installed - new ripple seen !

One CW inclinometry run was made Saturday afternoon. (Thanks Tom).

     dataset     Start time     Mean leg temperatures
                     HST        start   middle    end
   inc980222        10:45        1.8      2.6     3.6 C    cf
  (inc980214        10:55        7.2      8.6     9.7      
   inc980131        12:55        5.2      6.5     7.6       
   inc980124        12:30        8.4      9.6    10.4   
   inc971214        10:55        2.2      3.8     5.0   )

The plot below shows the difference between the model that this new data would generate and the current model, of 980214 :

Large 4-5" spikes at the usual positions, but in the opposite sense to that seen last week imply a reversion to the track state prior to 980214. Such changes in a timescale of a week are of some concern, and I repeat my request for inclinometry at any possible time. The data over the past couple of months do suggest a correlation between the size of thse spikes and ambient temperature. The plot below, for instance, shows a comparison of the data taken at the two lowest mean temperatures listed in the table above. The agreement is good, with rms scatters in the (F1,F2,F3) differences of (0.34",0.43",0.39"). More data are needed (as usual) to support any such putative relation.

The new model has been installed.

However, the above plot also reveals a ripple with a frequency of between 8.8 and 9.0 degrees and amplitude 0.5" (NB in model parameter space). Similar ripples seen in the spring of 1996 were judged a precursor to a possible wheel failure and lead to the replacement of the rear right wheel in April 1996. I can see some radial-arm inclinometry ahead . . . !!!

Later - further analysis reveals that

• the problem lies on the right side of the antenna,
• it occurred sometime between 14 Dec 1997 and 24 Jan 1998, and
• the amplitude of the problem has increased in the interim from ~0.5" (tilt of A-frame) to 0.8".