Example of an OOF analysis for the GBT

Observed data and analysis

The observed beam maps are shown in the first row of the table below. The are taken from our campaign to characterise the effect of gravity on the large scale wavefront errors. The date was 11th April 2005 (scan numbers 114ff). The analysis was done in the usual way. We show the best-fitting aperture and the best-fitting beams as the number of Zernike orders used for the fitting is increased.

A sample OOF observed data set (top row) and the results of analysis with increasing number of Zernike polynomials used to parameterise the aperture:

Observed beams   obsbeam-1 obsbeam-2 obsbeam-3
n=1   z1-f0 z1-f1 z1-f2
n=2 z2-ap z2-f0 z2-f1 z2-f2
n=3 z3-ap z3-f0 z3-f1 z3-f2
n=4 z4-ap z4-f0 z4-f1 z4-f2
n=5 z5-ap z5-f0 z5-f1 z5-f2
n=6 z6-ap z6-f0 z6-f1 z6-f2
n=7 z7-ap z7-f0 z7-f1 z7-f2
n=8 z8-ap z8-f0 z8-f1 z8-f2

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