[daip] questions regarding prtan and imagr

[Eric Greisen]

Hiroko Shinnaga wrote:
>
> It's good to know that UVPLT does not use the antenna table.  If I do PRTAN,
> the output for the 8 antennas looks reasonable, like
> 
> .............................................
> Array reference position in meters (Earth centered)
> Array BX=  -5462428.40757    BY=  -2491960.45618    BZ=   2286526.65343
> Polar X =   0.00000 Polar Y =   0.00000 arcsec
> Earth rotation rate =  360.9856449756 degrees / IAT day
> GST at UT=0 =  202.5367277361 degrees
> UT1-UTC=      0.0000000   Data time(UTC     )-UTC=      0.0000000 seconds
> Solutions not yet determined for a particular FREQID
> Mount=ALAZ  Axis offset=  0.0000 meters    IFA               IFB
> Feed polarization type =                    R                 L
>  
> Ant   1 = AN01     BX=        0.0000 BY=        0.0000 BZ=        0.0000
> Ant   2 = AN02     BX=       90.4130 BY=     -276.1790 BZ=     -263.6168
> Ant   3 = AN03     BX=       85.4508 BY=        1.9548 BZ=     -209.1038
> Ant   4 = AN04     BX=       37.0243 BY=     -405.5341 BZ=     -149.5777
> Ant   5 = AN05     BX=      154.5661 BY=      -60.0895 BZ=     -399.4778
> Ant   6 = AN06     BX=      128.0491 BY=       73.5067 BZ=     -295.3008
> Ant   7 = AN07     BX=      139.7886 BY=       19.8421 BZ=     -336.0244
> Ant   8 = AN08     BX=       -3.2893 BY=     -178.0796 BZ=       14.1085
> .............................................
> 
> So, I guess the antenna table is fine except for the fact that the other two
> antenna's information is not included.  Do you agree on that?
> 
It looks okay - try PRTAB to see if PRTAN is interpreting things oddly 
and omitting some display.

> If the antenna table is used only for the calibration process, would we
> expect that the final map after processing IMAGR should be correct as long
> as we process the calibration elsewhere?
> 

Actually the AN table is not even used in calibration so you should be 
able to
do CALIB (self-cal) when you get the imaging to work.

> 

> I understand IMAGR does not use the antenna table now.  From where does AIPS
> get information required for UVWTFN?
> 

The weights are with the data - displayed by PRTUV etc.  Check them that 
way.  The weighting in IMAGR is wuite complex - it does the weight 
summing and normalizing starting with the weights in the data samples 
themselves.  Note that those weights are assumed to be proportional to 
1/uncertainty squared.

Eric Greisen