[daip] [Fwd: Multiple problems in the Aips task UVCON [31DEC10]]

[Leonia Kogan]

Hi Subhashis

I wrote UVCON many years ago. The people have successfully used UVCON,
but, as I remember, none used the pointing error option. At least none 
has complained about this. So, please try to use UVCON without pointing 
error (bparm =-1,0) for the beginning and tell me the result please.

I am very busy now, so I can deeply look in UVCON in 2-3 days. I am sorry.

Leonid Kogan

Eric Greisen wrote:
> 
> ------------------------------------------------------------------------
> 
> Subject:
> Multiple problems in the Aips task UVCON [31DEC10]
> From:
> Subhashis Roy <roy at ncra.tifr.res.in>
> Date:
> Tue, 8 Feb 2011 01:12:54 +0530 (IST)
> To:
> Eric Greisen <egreisen at nrao.edu>
> 
> To:
> Eric Greisen <egreisen at nrao.edu>
> 
> 
> Hi Eric,
> 
> I am trying to use UVCON for simulating Pointing error during observations.
> However, I am finding several serious problems in it.
> Hence, I would start describing below parameters that partially work
> to ones those do not work.
> I first tried using SMODEL=1,0,-2000,0 for a frequency of 0.33 GHz
> for a source with a DEC=40 deg (All the parameters used are given as 
> attachment 'uvcon.srcmod.input') with the array file attached with this 
> mail ('gmrt.antenna.array', as for GMRT). Similar results are seen using 
> 'VLA-A_UVCON'.
> (1) For given pointing errors of several arc-minutes using BPARM(5),
> if BPARM(3)=0, it produces no visible pointing errors as checked using 
> VPLOT [expected pointing errors would change the flux values by ~3% for 1'
> pointing error for a source which is simulated ~35' away at half power
> point].
> (2) While using BPARM(6)=4, the beamwidth is supposed to be controlled 
> by BMAJ, BMIN and BPA. But, it is found to be only dependent on antenna 
> diameter given in INFILE.
> 
> More issues if I try using IN2NAME.
> 
> To use IN2NAME, I generated an UV data and CLEAN with IMAGR, resulting
> in 3 fields, each containg 1 point source of 10 Jy.
> The fields had no RA offsets, but DECLINATION offsets of 0, -1800, -2700
> respectively.
> Using these 3 maps with IN2NAME and NMAPS=3 and NCOMP=2, 2, 2
> and CMETHOD='DFT' in UVCON with APARM=0.33, 0, 40, -5, 5, 17.5, 16, 30, 0
> and
> BPARM=-1, 0, 1, 0, 60, 1, 60
> CPARM=0
>  generates UV data such that many baselines display (VPLOT) flux
>  density values of 30 Jy with flux density variation ~0.2% every 60
>  minutes controlled by BPARM(7) [input parameters are attached in
>  'uvcon.3src.input']. For a few baselines, for certain time periods, the
>  flux values also go to Zero.
> 
> This shows 2 types of problems.
> 1. The amplitudes are missing modulations as expected due to 3 well
>    separated sources [is not reading the headers of the 3 maps properly
>    ?].
> 
> 2. Peak flux density indicates the maps of the 3 fields are not multiplied
>    by the primary beam as expected. It appears that it assumed the 3
>    sources to be at the field centre [with offset=0] resulting is low
>    variation of flux density due to pointing errors.
> 
> Any idea or solution to what is going on ?
> 
> Subhashis
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Daip mailing list
> Daip at listmgr.cv.nrao.edu
> http://listmgr.cv.nrao.edu/mailman/listinfo/daip