Technical Issue: Is OTF polarimetry possible?

claw
Posts: 26
Joined: Mon Mar 03, 2014 7:18 pm

Technical Issue: Is OTF polarimetry possible?

Postby claw » Fri Apr 04, 2014 12:45 pm

I just had an idle thought and realized I didn't know the answer...
Can we actually do accurate polarimetry with OTF scanning? It seems that OTF basically requires wide-field polarimetry at every point in the survey. I don't see the path for that in our calibration process, but I haven't looked in detail.

casey

smyers
Posts: 29
Joined: Mon Sep 09, 2013 4:43 pm

Re: Technical Issue: Is OTF polarimetry possible?

Postby smyers » Fri Apr 04, 2014 12:57 pm

OTF polarimetry is no different (or only slightly different) than interferometry with classic stepped mosaics. I guess we will know the answer since we took our S-band Stripe82 survey in full polarization. Preshanth and Russ Taylor also have some C-band observations in stepped mode that look pretty good so far. The polarized primary beam is more important then in imaging of course, and we are in the process of mapping this. I think the limiting issue will be what the needed dynamic range is.

claw
Posts: 26
Joined: Mon Mar 03, 2014 7:18 pm

Re: Technical Issue: Is OTF polarimetry possible?

Postby claw » Fri Apr 04, 2014 5:04 pm

I chatted offline with Steve on this, but to close the loop...
My concern was that each point in the final map comes from a set of integrations that are pointed differently (within a primary beam width). Steve's rebuttal is that we already needed to know the wide-field polarimetric response for fixed-grid surveys like FIRST/NVSS. The main difference is that OTF scanning will need to have these corrections applied for each integration. This has computational requirements that have not been quantified and, more importantly, we still need those calibration products for the JVLA.
Given these issues, I think we'll need to carefully vet the polarization science that we commit to doing.

casey


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