[daip] calibration against UV data

[Eric Greisen]

Huib Intema wrote:
> Dear Eric,
> 
> In my direction-dependent ionospheric phase calibration scheme, I want 
> to be able to calibrate stokes I UV data for direction-independent 
> antenna-based amplitude variations. There is no single action you can 
> perform to remove direction-dependent phase errors from your UV data, so 
> using CALIB to amplitude calibrate against a target field source model 
> is incorrect.
> 
> What I would like to do is to calibrate the observed UV data against 
> model UV data that I generate myself. The latter can be created from the 
> source model while applying the (inverted) direction-dependent phase 
> corrections. Is this possible within AIPS?
> 
> A possibility I thought about is to divide the observed UV data by the 
> model UV data, and subsequently CALIB the output against a 1 Jy point 
> source model. This operation is not equal to my previous suggestion, but 
> might work. Within AIPS, the only task that I could find for dividing UV 
> data sets is DIFRL, but attempts to create a fake RRLL UV database using 
> DBCON with the observed (stokes I) UV data turned into RR and the model 
> UV data turned into LL (through PUTHEAD CRVAL2=-1/-2 and CDELT2=-1) did 
> not work: DBCON says "STOKES RANGES DO NOT OVERLAP". Is there some way 
> to make this work, or is there another way to divide UV data sets?

I have added OPTYPE = 'DIV' to DIFUV which I believe will do what you 
need.  The MNJ on 31DEC09 tomorrow will pick up this change.

Cheers,

Eric Greisen