[evla-sw-discuss] Switched power calibration at the EVLA

[Michael Rupen]

> nominally could just store an weighted averaged Tcal number for each power
> measurement (e.g. 1 per spw).  How is it intended to use Tcal in the data 
> channels versus the wider band power measurement band?  I presume we scale 
> the
> r_ijf (f=channel within a spw) by a single factor over that spw (the rest 
> coming
> out in bandpass)?


That's my thinking.  With only one set of power measurements for a given
subband I don't see that we can do any better.  Of course this may muck up the 
bandpass a bit.


> SysCal versus new SysPower table: I don't know why ALMA would object to us 
> having a new (optional) table for our measurements rather than adding extra
> columns to the SysCal table, but thats above my pay grade.

Ditto ;)


> ALMA calibration: there seems to be info at
> https://safe.nrao.edu/wiki/bin/view/ALMA/CalPlan
> but there may be updated documents in EDM (Nuria?).


See also Robert's nice description of the Calibration Data Model --
the tables are superceded by those in the SDM documentation, but the
outline of their use is quite nice.  Basically ALMA maintains a separate
Calibration Data Base and either the archive or CASA fetches the appropriate
calibration information when loading or dealing with the data.  I'd
thought this was the archive but can see benefits to CASA accessing that
archive directly as well.  I have a few worries about this approach; probably
the major one is the difficulty of assigning validity intervals, and choosing
which of several overlapping intervals you want.  There's also no place
in their system for decisions based on distances rather than simple times --
i.e., you always take the nearest calibration in time and ignore how far
away the calibrator is from your source.  But those are details.

This and other SDM-related documentation may be found at

    http://www.aoc.nrao.edu/~mrupen/SDM/sdmdocs.html

I suppose I should start putting in links for calibration as well.

              -- Michael