[evlatests] WIDAR bronze dataset - C band dual pol.

[Frazer Owen]

Michael Rupen wrote:
>
>> I agree with Frazer that the TSYS should give good estimates of the
>> weights.  However, FIXWT does a good job in determining what the
>> post-fit (remove the image, look at the rms in the data, baseline by
>> baseline or antenna-based) weighting really should be (caveat: my last
>> use of FIXWT showed some problems in the technique, mainly too short of
>> an averaging time).  In my experience, fiddling with the weighting
>> properly does decrease the SNR on the image at the 10 percent level
>> (assuming no bad antennas with too high weights are included), but with
>> little change in the remaining artifacts.  So my guess is that you don't
>> have a major weighting problem, but something more fundamentally strange
>> with the data.
>>
>> Ed
>
>
> We're doing quite odd things with WIDAR-0 compared to normal
> observations -- attenuators fixed, no scaling by total power, no Tsys
> scaling, etc. etc.  The weights used in imaging, unless you take special
> care, will reflect the scalings required to account for all this, and may
> wind up very odd indeed.  So a priori it's not obvious that one wouldn't
> gain quite a bit from putting in proper weights...in fact I'm a bit
> surprised Vivek's tests don't show a bigger effect.
>
> As I mentioned to Frazer, one might do better by deriving rms from the
> scatter over channels than over time, for WIDAR data.  Assuming no lines,
> ignoring RFI, etc. :}
    I don't that will work unless there are no sources.
>
>              Michael
>