[mmaimcal]Change to Total Power Detector sampling rate

[Jeff Mangum]

Hi Al,

Thanks.  I have added this to the Total Calibration discussion wiki
at:

https://wikio.nrao.edu/bin/view/Main/AlmaTotalPower

Cheers,

Jeff


"Al" == Al Wootten <awootten at nrao.edu> writes:

Al> Mark had another point, which I try to paraphrase thusly: Currently, our
Al>   paradigm is a 5% error in the relative flux scale.  This will not be
Al>   good enough for some mosaicked observations, where such a large
Al>   difference in the interferometer flux scale and the total power flux
Al>   scale will result in imaging errors. How can we improve this?  Mark
Al>   proposes we contemplate a cross calibration of total power and
Al>   interferometric systems by observing a bright quasar with both. At 880
Al>   GHz there should be one 0.5 Jy QSO within 15 degrees or so of the mosaic
Al>   target source.  We can observe that source, but ideally the minute or so
Al>   we'd like to devote to getting good enough S/N on that source will not
Al>   suffice.  We'd need many minutes, perhaps an hour.  But in that period
Al>   of time the sky and the instrument are likely to have changed, so we
Al>   cannot get adequate S/N quickly enough.  However, if we observe with all
Al>   64 antennas, although the TP flux scale on any particular antenna may be
Al>   say 8% off, the mean of all of them would be like 1% off, enabling the
Al>   accurate cross calibration of total power and interferometric
Al>   observations, and allow us to make a high quality mosaicked image.

Al>   I believe that the change should apply to all 64 antennas.

Al>   Comments?  Corrections?

Al> Mark notes that you can also find backing material for this argument in
Al> section 10.2 of https://wikio.nrao.edu/bin/view/ALMA/CalTotalPower

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