In order to avoid having to fully calibrate differential Faraday rotation, we can convert the data to a circular polarisation basis. Some details of early attempts can be found here.

This is currently done in own prototype-software. In the near future we want to implement this as part of NDPPP or in a simple standalone program.

Note that this is not about the final version of Tobia's converter. It will be updated as soon as possible.

I tested Tobia's converter (version of 9th March 2012) on the data set L30253 (observations of Jupiter 6th August 2011). Earlier conversions to circular can be found in this presentation on slides 24/25. There are large regions with strong right-handed circular polarisation and smaller ones with left-handed polarisation.

A new conversion to circular using Tobia's script can be found in this PDF. Page 1 has RR, 2 has LL. Note that the colour map and scaling is different from the earlier presentation. For other purposes I wrote another quick-and-dirty converter using the same geometric model as before. Results are shown here.

There seem to be two problems at the moment:

• The separation between LL and RR does not work perfectly.
• There is a amplitude problem close to the end of the observations.

We have to compare the Jones matrices that are actually applied, find out which ones is correct (if any) and fix the other one.

[ widemap: astro_wm/lofar_obs_wm/L2011_30253 and /PLOTS, MS in widemap9:/export/scratch/wucknitz/temp ]

— Olaf Wucknitz 24-Mar-2012 21:04