D3A Radiation Pattern Measurement

One of the D3A experiments is to determine the radiation patterns of the test dishes by using drift scans of bright astronomical sources. These will be one-dimensional cuts through a 2-D radiation pattern. Here's a picture showing this, with the black horizontal line representing the path of a radio source through the telescope beam:

If the elevation angle of the dish is changed by some fraction of a beamwidth between drift scans, then the radiation pattern is sampled like this:

Questions:

• What is the size of the elevation angle steps? Nyquist sample?
• How many elevation scans/cuts are required?
• How to separate dish positioning errors from dish surface errors?
• Is it possible to take scans at different elevation angles (taken on different days) and then to align and Fourier transform to estimate the surface of the dish (i.e holography)?