[daip] questions regarding prtan and imagr
Leonia Kogan
lkogan at nrao.edu
Tue May 13 17:43:45 EDT 2008
Hiroko Shinnaga wrote:
> Hello Leonia,
>
> Thank you for your response to my questions. I have further questions.
>
>
>> Q1
>>
>>
>>> When I inspect the data using the task "UVPLT"
>>> for example, it looks like it contains all data of all baselines.
>>>
>> Yes the data include probably all baselines.
>> UVPLT plots the UV data and does not use AN table at all.
>> I think your AN table is actually corrupted. I do not know MIR(IDL).
>> So I do not know why the AN table is wrong.
>>
>> Generally speaking AN table is used at the calibration (at AIPS). So if you
>> used
>> the AN table at MIR(IDL) your calibration could miss the 2 antennas depending
>> on your
>> input parameters.
>>
>>
>
> 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?
>
I am not familiar with your array coordinate system. It looks like the
coordinate system is similar to VLA:
the origin is at the array center; the position of the center is given
at Array BX= ....
But the details like right or left hand... should be addressed to yourself
> 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?
>
Yes, if the U,V,W attached to each visibility is correct
>
>
>
>>> Q2. When I tried to process the above image with IMAGR, I found
>>> I was able to make sensible image only when I use UVWTFN = ' '
>>> (uniform weighting). Does this indicate that something may be
>>> wrong for the table that contains weighting information of each antenna?
>>>
>> In AIPS AN table is created by the task FITLD
>>
>> Q2
>>
>> IMAGR does not use AN table at all
>>
>>
>
> I understand IMAGR does not use the antenna table now. From where does AIPS
> get information required for UVWTFN?
>
IMAGR works with visibilities. Each visibility includes:
real, image part of the visibility;
U,V,W corresponded to visibility. Pay attention UVW of the baseline
at coordinate system related with the source
picture plane, but not antenna
and many other parameters.
Usually U,V,W is calculated by the correlator and (I repeat) is
related with the visibility
About UVWTFN:
This is input parameter of IMAGR.
IMAGR uses U,V,W differently depending on UVWTFN
>
> Hope to hear from you. Thanks very much.
>
> Hiroko
>
>
>
> On 08.5.13 10:07 AM, "Leonia Kogan" <lkogan at nrao.edu> wrote:
>
>
>> Hiroko,
>>
>> The main person of AIPS Eric is not at the office now. So I'll try to
>> answer you something.
>>
>> Q1
>>
>>
>>> When I inspect the data using the task "UVPLT"
>>> for example, it looks like it contains all data of all baselines.
>>>
>> Yes the data include probably all baselines.
>> UVPLT plots the UV data and does not use AN table at all.
>> I think your AN table is actually corrupted. I do not know MIR(IDL).
>> So I do not know why the AN table is wrong.
>>
>> Generally speaking AN table is used at the calibration (at AIPS). So if you
>> used
>> the AN table at MIR(IDL) your calibration could miss the 2 antennas depending
>> on your
>> input parameters.
>>
>> In AIPS AN table is created by the task FITLD
>>
>> Q2
>>
>> IMAGR does not use AN table at all
>>
>> So all your problems are at the beginning: outside of AIPS !!!
>>
>> Leonid Kogan
>>
>>
>> Hiroko Shinnaga wrote:
>>
>>> Dear AIPS experts,
>>>
>>> I'm Hiroko Shinnaga, a staff scientist at the Caltech Submillimeter
>>> Observatory. I have two general questions regarding tasks of PRTAN
>>> and IMAGR.
>>>
>>> Q1. I'm dealing with some interferometric data that contains
>>> 10 antennas in total. I first create FITS file using a calibration tool
>>> called MIR (IDL base) and generated a FITS file. Then I read the
>>> FITS file to AIPS. When I inspect the data using the task "UVPLT"
>>> for example, it looks like it contains all data of all baselines.
>>> However,
>>> when I use the "PRTAN", I see only information of 8 antennas. From
>>> the output of "PRTAN", it seems the antenna table seemed to not be
>>> transfered properly. Could you let me know what kind of effect I
>>> should expect if I don't have a correct antenna table?
>>>
>>> Q2. When I tried to process the above image with IMAGR, I found
>>> I was able to make sensible image only when I use UVWTFN = ' '
>>> (uniform weighting). Does this indicate that something may be
>>> wrong for the table that contains weighting information of each antenna?
>>>
>>> Hope to hear from you. Thanks very much.
>>>
>>> Hiroko
>>>
>>>
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>>>
>>>
>
>
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