Bayesian retrieval of water vapour column

This week I've been in part working on Bayesian retrieval of water vapour column from prototype WVR data.

The attached plot shows a typical result: It shows the retrieved *zenith* water vapour column as a function of time while the telescope was tracking a source for about an hour (it was setting at the time). The colour scale represents the posterior distribution and is hence an indication of the confidence in the retrieved values.

You can find out more detail on the retrieval method in my most recent talk at these web pages:

http://www.mrao.cam.ac.uk/~bn204/publications/publicationlist.html

casa-core

I've recently tried to build casa-core (http://casacore.googlecode.com) and found that it is surprisingly easy to build on my laptop system (Ubuntu/8.10 32bit). In fact, the only configuration item that required any fiddling was the build of the WCS library. The main gripe is excessively long compilation time.

In order to make management of the casa-core source more flexible, I used the bazaar version control system (http://bazaar-vcs.org/) and the bzr-svn plugin to check-out the casa-core source code. This allows some significant advantages compared to plain SVN :

* Access to full history information without connection to the
internet

* Ability to make local branches

* Ability to layer local changes on top of the revisions contained in
the SVN

If you want to know more, feel free to write to me...

We will be using casa-core to, at the very least, access Measurement Set data produced by ALMA.

Talk at Charlottesville

The talk I gave in Charlottesville is available at:

http://www.mrao.cam.ac.uk/~bn204/publications/2009/NRAOJan09followup.pdf

Visiting NRAO/Charlottesville

For the first part of this week I'm visiting NRAO Charlottesville offices: http://www.nrao.edu/

Talk at the URSI NA meeting in Boulder

I gave a talk about ALMA phase correction and calibration at the URSI
meeting in Boulder. The PDF is available from the usual place:

http://www.mrao.cam.ac.uk/~bn204/publications/2009/NikolicURSI09.pdf

Calculating dispersive path delay due to the atmosphere

I've posted a simple command-line program to compute the dispersive path delay due to the atmosphere using ATM (more precisely my re-packaging AATM). The program is available at:

http://www.mrao.cam.ac.uk/~bn204/alma/aatm-dispersive.html

I had not appreciated that even at 330GHz, the dispersive wet delay is about 10% of the non-dispersive wet delay.

Out-Of-Focus holography with mm-wave cameras

Recently, we (meaning the groups at NRAO, at University of
Pennsylvania and myself) have made progress on enabling the OOF
holography technique (see http://www.mrao.cam.ac.uk/~bn204/oof/) on
large-format radio wavelength cameras, in particular the MUSTANG array
at the GBT.

This work is being documented on the following wiki:

http://wiki.gb.nrao.edu/bin/view/PTCS/OOFHolography

The oof software is available for download at:

http://www.mrao.cam.ac.uk/~bn204/oof/software.html

Finally, as an illustration, below is a map of the GBT surface
re-created from out-of-focus MUSTANG images. Although this particular
observation took of the order of 15 minutes, it is likely we will be
able to reduce this to the order of a couple of minutes, allowing
effective and rapid correction of all gravitation and thermal effects
on the telescope.