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Comparison of values for the rms surface accuracy

From RxH3 data we obtain several different values for the rms surface accuracy of the dish -
See the summary plot with the results of a 160 GHz map:

The usually quoted rms derived from RxH2 data is the rms of all 828 moves of the adjusters ('Adjuster rms' in the above figure).

The unweighted rms of all data points in the RxH3 map (except the areas around the shadows of the SMU support legs that are masked)
is 'Aperture rms' in the figure.
However this rms is not uniform: values for the 7 rings of the telescope are for the map shown:
32.2 (ring 1), 25.9 (ring 2), 22.9 (ring 3) 26.4 (ring 4) 24.8 (ring 5) 32.8 (ring 6) 48 (ring 7) 34 (total)

Weighted with the average edge taper of JCMT receivers of 10 dB this rms then is 32.8 micron.

From the derived surface accuracy over the dish one can obtain at different frequencies a far field pattern, which can be compared
with that of a perfect dish. This gives us values for the 'Ruze rms' in the plot, which decrease somewhat with increasing frequency.

We are working on the reduction of older RxH3 maps that were taken the same day as RxH2 maps, to be able to compare results from both receivers.

Last modified: 13 December 2002
Jan Wouterloot

j.wouterloot@jach.hawaii.edu

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Contact: Jan Wouterloot. Updated: Tue Jun 20 17:03:03 HST 2006

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