[evlatests] your mail (Antenna Wrapping)

[Ken Sowinski]

On Mon, 8 Mar 2010, David Harland wrote:

> Yes, the OPT allows the user to provide wrap hints for each scan.
> The scan's default is "No Preference"; the user may change this
> to CW or CCW.
>
> The script generation process sets the wrap for every scan, using
> -1 for CCW, +1 for CW, and 0 for no-preference.
>
> Questions:
>
> 1. Should we do as Ken suggested and suppress the
> subarray.setWrap cmd if the user expressed no preference?

> 2. Is there any harm in sending the same setWrap cmd
> (eg, setWrap(-1)) on successive scans, as we do
> currently?

The way the executor works, once a a wrap hint is supplied
it is used for every scan thereafter.  A (non-zero) hint
should be supplied for scans which the observer knows from
global considerations will leave the antennas in the wrong
wrap sometime in the future.  It is usually a good thing
to specify 'left' wrap if beginning a file looking in the
East, and 'right', when beginning a file looking in the west.
Like all general rules, there may be exceptions.  The following
scan should be marked 'don't care'.  If I think hard enough
I might be able to come up with examples where doing otherwise
would be counter-productive.

Ken