Theodolite survey of dome from ao9 monument july03

Jul. 2003

links to plots:
The pitch, roll, focus errors (relative to the reflector) from the theodolite survey

links to sections:

Intro

The elevation rails were shimmed and the dome lifted 1.65 inches in feb03. A theodolite survey from ao9 was done on 17feb03. This was before all of the final adjustments were done (see feb03 survey). A survey from ao9 to measure the shimming/domemotion results was done on 09jul03 followed by a nights worth of az, za spins using the tilt sensors. Below is a summary of the theodolite results. Pitch, roll, and focus errors as derived by lynn baker from the theodolite measurements are plotted. Lynn used the center of curvature as the reference (not ao9).

09jul03 The theodolite results (top)

A survey was done from ao9 on 09jul03 starting at 10 pm and going until 3 am. 2 za strips were done at az=242.87 and az=302.87 followed by two azimuth swings at za=5 degrees and za=15 degrees. The data was reduced by lynn baker and the pitch, roll, and focus error were computed relative to the reflector center of curvature (as computed by lynn). The tiedowns were left off during the measurements. The average height of the platform from the distomats was 1256.23 feet. The platform moved about .2 inches in height (up) during the 5 hours of the measurement. The pitch, roll, focus errors (relative to the reflector) from the theodolite survey (.ps) (.pdf) are shown in the plots. The jul03 data is compared with the data taken on 17feb03 (towards the end of the shimming).

Fig 1 top. This is the pitch (black) and roll (red) errors for the zenith angle strips. The curves with * are the za strip at azimuth 242.87 (pointing at T8). The curves with + are the za strips at azimuth 302.87 (between T8 and T12). The errors are within .1 degrees down to about 3 degrees za.
Fig 1 bottom. This is the focus error for the za strips using the center of curvature of the dish as the reference. The left axis is in inches, the right axis is in centimeters. * is the az swing at 5 degrees za while + is the az swing at za of 15 degrees. The +/- 3 cm dotted blue line is focus error that gives a 3 db loss at 10 Ghz.
Fig 2 top. The pitch and roll error for the azimuth swings. * is the az swing at 5 degrees za while + is the az swing at za of 15 degrees. The purple points are the common points (in az, za) that were measured by the za strips. They differ by up to (.01 degrees).
Fig 2 bottom: The focus errors for the azimuth swings. The common points from the za strips are over plotted in purple. They differ by up to .25 inches.
Fig 3. The pitch and roll are added in quadrature with the focus over plotted. Use the left axis to read the degrees for sqrt(pitch^2+roll^2) and use the right (blue) axis to read the focus error in cm. The top plot are the za strips while the bottom plot has the az swings.
Fig 4. During the measurements, the tiedowns were turned off and the distomats were reading the height of the platform once a minute. Fig 4 is the variation in the height of the platform from the average value (curval-meanvalue) for the 5 hours of the observations. The units are inches. The mean value used was 1256.235 feet. The colored portions show the 2 za strips and the 2 az swings. You can see that going from red (za=19.6,az=242.87) to green (za=19.6,az=302.87) caused the average height of the platform to move by about .1 inches. This is probably an error in the measurements since the total weight on the platform did not change and the temp did not change that rapidly. On the other hand, the end of the red strip (az=242.87,za=15) and the end of the purple strip (az=242.87,za=15) were at the same az, za so the platform did move by about .2 to .25 inches over the measurement.

The maximum pitch, roll error (added in quadrature) is about .12 degrees (staying above za=3). The focus error goes from about -1.8 to 1.8 inches. There is an error in the measurements caused by the drift of the platform during the measurements of about .25 inches. I guess i could take a linear ramp out of the focus error (with cos(za)) and ignore it's affect on the pitch,roll (or lynn could rerun the data...). We need to verify that the focus position used (center of the reflector) corresponds to the focus position that maximizes the focus curves. In the past they were off by 1 to 2 inches.

Processing:survey/030709/reduc/comparesurvey.pro

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