[daip] New Ticket - [!WXZ-469522]: FRPLT

[Vivek Dhawan]

New Ticket: FRPLT

FRPLT  is showing extreme sensitivity to certain values of input parms, and
making artifacts under these conditions (tst & new versions). 

I would rate this as a low priority fix since only Rick and I use the program, but we  do find it extremely useful to track down errors in various parts of the system, from hardware (LO wobbles) to correlator software (e.g. 10sec updates of phase/delay models) to 'fast WIDAR wobbles' of yet-unknown origin.

here are the specific pathologies:

A. set timerange, say 5 min.  set aparm = 1, 0; i.e. set input integration =1sec.
    set solint=5min; run ==> makes false sidelobes (in this case at 11s period
    or 90mHz) on perfectly good data.

    Same paramaters & data as above, set solint=0  ==>  sidebands go away.

B. same data; same inputs; set solint 5min; 
    set aparm(1)=1.0; get false 90mHz sidebands.
    set aparm(1)=0.999 or 1.0001 and the sidebands go away.

I dumped some data out using UVPRT (which rounds the time to nearest
second so I discarded the time label and just used the index # of the data)
There are no 11s modulations visible either by eye or after DFT outside AIPS.

as i understand it aparm(1) is used to scale the X axis from index to fringe-rate
frequency after the FFT;  so lying to the program should just scale the axis (it
does behave this way for e.g. aparm(1)=2 on actual 1s data makes a plot whose x-axis is scaled by a factor 2; but near aparm(1)=1 the behaviour is singular somehow.

here is a FITS file to test it on:

/home/aakash2/AIPS/DA01/FITS/FRPLT.FITS

and here is a plot of behaviour (A) above. i.e.  Blue is good, solint=0;
red is bad, solint =4min=timerange; both have aparm 1,0. green is the
overlap. 
                
/home/aakash2/AIPS/DA01/FITS/FRPLT.PS

 B makes plots just like A.


Ticket Details
===================
Ticket ID: WXZ-469522
Department: Data Processing (AIPS)
Priority: Default
Status: Open
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=97