[Difx-users] Handling lin-pol data with difx2fits

[Rick Perley]

     All:

     AIPS now does to linear polarization quite nicely.  See the EVLA 
Memo (#207) that Eric Greisen and I just submitted.

Many changes were needed to ensure the correct combinations, and order, 
were made.  Eric can provide details, if needed.

     Rick


On 04/11/2019 01:44 PM, Leonid Petrov wrote:
> Dear Walter,
>
>> It is true that the poltype is hard coded.  With some experimentation we
>> might be able to change that to X/Y as aspropriate.  At one point I
>> believe AIPS had trouble with other than R or L.  We can look into this
>> for DiFX 2.7.
>    If AIPS at the moment has troubles with other than R and L, we can
> ask Eric just to patch AIPS to treat X and Y or H and V as R and L on the flight
> temporarily until better time come, if it is necessary. It should not take more
> than 5 minutes. From the other hand, I got an impression that some folks
> already used AIPS for processing lin-pol data. Am I wrong? If yes, how did they
> do it?
>
>    I have 6 lin-pol experiments on my table and a hundred or so to come within
> weeks. We have to fix it now, i.e. today.
>
>> As noted above, the FITS format is unable to describe such data, so this
>> is not possible.
>    Although I heard a combinations of words "possible" and "not", I still cannot
> grasp what do they mean together. We need amend FITS-IDI, I understand it.
> So what? Even the US Constitution was amended, and more than once. Let us
> discuss how to do it. And we need fix difx2fits: today it tells that it does not
> like a combination of lin- and cir- data and stops. Yes, we already have the
> lin-cir and cir-lin data that need to be processed, and we plan to get more data
> like that. I already rolled my sleeves up and ready to do it. If you or anybody
> else can provide ideas and/or guidance, warn about pitfalls, contribute code, etc,
> I will appreciate it. But I cannot just do nothing and say: "these are the data that
> I cannot process". Failure is not an option.
>
> Sincerely,
> Leonid
> 2019.04.11_15:38:06