Changes/invert

invert
Item	Complexity	Research	Milestone	Time
Theoretical Noise	easy	moderate	6	5d
Visibility Weights	easy	moderate	6	5d
Primary Beam	moderate	some	10	2-5d
MFS	moderate	some	11	15d

Theoretical Noise

Use Tsys spectrum for computing theoretical noise in image.

Visibility Weights

Use Tsys spectrum for determining weights in image formation.

Primary Beam

Check and, if necessary, correct usage of primary beam models in invert. Make sure variation with frequency is taken into account for mosaic case. Amount of time needed will increase if current code is not handling this correctly. Should check linmos, mossdi and mosmem as well, hopefully they share the primary beam code...

Multi Frequency Synthesis

Add a spectral curvature term (2nd order term) to MFS imaging. At present the average flux and a spectral index are handled. For 2-4 GHz bandwidth we may require higher order terms to model the sources in a typical field, especially at the lower frequencies. Some research is required to determine whether this is indeed a limiting factor in high dynamic range imaging and how much improvement can be expected.

Questions

• If we split the UV data into dozens of files all separately calibrated, what is the max. number of UV data files invert will accept?
• We could just glue all the pieces together for spectral line data, but what about the continuum multifrequency synthesis case?
• Look at the code to find out: does invert process channels independently with regard to multi frequency synthesis?

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