The SPECSYS header in FITS files defines the spectral system (topocentric, barycentric, LSR, etc.) of the data stored in the files. For Arecibo observations, the data is always stored in topocentric frequency, even if the data was taken with doppler tracking in another spectral system. Unfortunately, the CIMAFITS files produced by the WAPP spectrometers store the spectral system used for doppler tracking in the SPECSYS header. While this is not a problem for data reduced using AOIDL, this will lead to the frequencies being interpreted incorrectly by standard FITS readers.

Mikael Lerner has written a short c program to correct this problem. This can either be run using /share/rminchin/progs/corr_fits ⟨filename⟩ or downloaded from here and compiled locally, using the same syntax. Note that the program will overwrite the original file so be sure to work on a copy of your data!

The c program runs on only a single file at a time and does not take wildcards. In order to convert a number of files, a perl script has been written to call the c program repeatedly. This can be run using (for example) /share/rminchin/ *.fits to correct every fits file in a directory. For running elsewhere, the script can be downloaded from here - note that the location of the compiled ‘corr_fits’ program will have to be edited to relect its location on your system.