[daip] modification to WTMOD

[Eric Greisen]

Andy Biggs writes:
 > Hi there. I was wondering whether it would be possible to modify WTMOD. I 
 > would like to give it a number *per antenna* which could then be used as a 
 > multiplier for the existing weights to that antenna. At the moment the 
 > multiplier is single valued i.e. the weights on each baseline are scaled 
 > identically. Perhaps the ANTWT array could be viewed as containing either 
 > absolute weights or scaling factors, which being dependent on some other 
 > parameter.
 > 
 > At the minute, the standard MERLIN data reduction path makes no attempt to 
 > calibrate the relative antenna weights based on initial gross amplitude 
 > corrections from a flux calibrator. Instead, WTMOD is used to insert 
 > nominal values for each antenna's weight, after calibration (i.e. just 
 > before mapping). This however loses weight info which has been gleaned 
 > during amplitude calibration using the phase reference source; data at low 
 > elevation, for example. If instead the nominal weights could be used as 
 > multipliers, then this useful information could be retained.
 > 

this was added to WTMOD some time ago - perhaps I forgot to tell you.

Eric Greisen