What’s in my data?

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1.5.4 What’s in my data?

The actual data is in a large MAIN table that is organized in such a way that you can access different parts of the data easily. This table contains a number of “rows”, which are effectively a single timestamp for a single spectral window (like an IF from the VLA) and a single baseline (for an interferometer).

There are a number of “columns” in the MS, the most important of which for our purposes is the DATA column — this contains the original visibility data from when the MS was created or filled. There are other helpful “scratch” columns which hold useful versions of the data or weights for further processing: the CORRECTED_DATA column, which is used to hold calibrated data and an optional MODEL_DATA column, which may hold the Fourier inversion of a particular model image. The creation and use of the scratch columns is generally done behind the scenes, but you should be aware that they are there (and when they are used). We will occasionally refer to the rows and columns in the MS.

More on the contents of the MS can be found in § 2.1.

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