Stores the spectrum defined by the variable Spec at the pixel position [ix,iy] of the time slot it. The spectrum Spec is a general spectral format (array of spectral points).
The spectral values written into the data cube at pixel [ix,iy] are interpolated from the spectrum Spec. If Spec does not cover parts of the cube, zero values are stored at these wavelengths. If Spec extends beyond the data cube the extra spectral values are ignored.
The function returns the following error codes:
0 ... everything is OK
-1 ... invalid spectral group
-2 ... ix or iy is out of range
-3 ... it is out of range
-4 ... the number of spectral points must be greater than 1