Data inspection

Have a look at the FITS header by typing imhead (imh). This will report various information about the FITS file including the number of IFs (sub-bands), the number of frequency channels per IF, the observed frequencies and the number of Stokes parameters. There are a number of other tasks that should be run on the data, some of which already form part of the pipeline output. These are,

• LISTR: Run with OPTYPE='SCAN' this task will produce a listing of every scan that is included in the multi-source file.
• PRTAN: You will often need to know the number that AIPS assigns to each antenna.
• VPLOT: Looking at amplitudes and phases with time (BPARM=0,-1) and weights with time (BPARM=0,16) is recommended.
• UVPLT: The main use of this task is to plot amplitude and phase against (u,v) distance although it is also useful for making plots of the (u,v) coverage (BPARM=6,7,2,0).
• POSSM: Running this (on short segments (about 1 min) of data) with APARM(9)=1 will plot the amplitudes and phases as a function of frequency for each IF. It is also a good idea to look at the auto-correlations in POSSM (with APARM(8)=1) as these can reveal channels that are affected by RFI. Note, however, that if the data were correlated before 2003 June 1, their amplitudes cannot always be trusted due to normalisation errors in the correlator.

Various plots of the NME experiment N02L1 can be seen in Figs 1, 2 and 3. Also, tables of possibly useful parameters of the EVN telescopes can be found at the EVN status table.