’briggs’ weighting

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5.2.11.5 ’briggs’ weighting

The weighting = ’briggs’ mode is an implementation of the flexible weighting scheme developed by Dan Briggs in his PhD thesis. See:

http://www.aoc.nrao.edu/dissertations/dbriggs/

This choice brings up the sub-parameters:

weighting      =   ’briggs’   #   Weighting to apply to visibilities
     robust    =        0.0   #   Briggs robustness parameter
     npixels   =          0   #   number of pixels to determine uv-cell size 0=> field of view

The actual weighting scheme used is:

ωi wi = -------2- 1+ Wkf

(5.9)

where W_k is defined as in uniform and superuniform weighting, and

(5* 10-R)2 f2 = --∑--W-2--- -∑k-ωk i i

(5.10)

and R is the robust parameter.

The key parameter is the robust parameter, which sets R in the Briggs equations. The scaling of R is such that R = 0 gives a good trade-off between resolution and sensitivity. The robust R takes value between -2.0 (close to uniform weighting) to 2.0 (close to natural).

Superuniform weighting can be combined with Briggs weighting using the npixels sub-parameter. This works as in ’superuniform’ weighting (§ 5.2.11.3).

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