RE: [alma-sw-ssr] Offline and Pipeline Requirements

[Mark Holdaway <mholdawa@nrao.edu>]

> 
> Tim,
> 
> 	It's good to have your participation, and know what
> to expect.
> 
> If there is a significant increase in image fidelity by
> going back to the uv-data in the deconvolution of mosaiced
> images, then this has a very significant effect on the operational
> model for ALMA image analysis.
> 
> It remains to be demonstrated that there is a meaningful
> increase in image fidelity with telescopes with real pointing
> and other errors, and what the cost in performance is.
> 
> These tests should be done as soon as possible, and I would be happy
> to provide some data. The attached MIRIAD script, takes
> about 5 min to make images, 10 min for SDI and 20 min for Maxen
> on a sun ultra 10 (93000 uv-points and 19 pointings and 64 channels).
>  The numbers can be scaled appropriately for ALMA.
> 
> 		cheers,
> 
> 			Melvyn
> 


Mel,

I think the whole point is that we can't allow our experience with a 9
element interferometer with maximum dynamic range of 200:1 to limit our
understand of what is required of the data reduction on a 64 element
interferometer which will potentially have a dynamic range of many
thousands to one.

If there is any hope of correcting for pointing errors, it is through
algorithms which combine pointing self-calibration with the deconvolution,
ie, knowledge of the visibility data is directly tied together with the
process of imaging and deconvolution.  This is the strength of AIPS++,
and it will be somewhat difficult for less developed radio-synthesis
software to deal with such problems and impossible for software such
as IDL to deal with them.

	-Mark