[CALIBRATE\]TRANSFORM FFT FileIn FileOut [Nchan]
Compute the Fourier Transform of FileIn along the Frequency/Velocity ax-
is. The direction of the Fourier Transform depends on the nature of
FileIn.
If FileIn is a standard Data Cube, a direct Fourier transform is per-
formed, that leads to 4-D cube as FileOut, in order (position,posi-
tion,complex,velocity). Its 3rd axis has 2 pixels that contain the Real
and Imaginary parts. The number of channels is extended to the nearest
integer of the form 2^n 3^p 5^q where p and q are less or equal to 2.
Conversely, if FileIn is such a 4-D cube, an inverse Fourier transform
is performed, leading to a (position,position,velocity) cube as FileOut.
Optionally, Nchan can specify how many channels are actually retained in
this case.
Gildas manager
2023-06-01