Setting the source velocity
Keywords: class-herschel-fits

Next: Going from to Up: Quick start guide Previous: Associated Arrays Contents

##
Setting the source velocity

The spectra are imported assuming a zero-valued velocity of the source in the LSR frame. This most probably implies that the line frequencies will appear redshifted. The standard use of CLASS is to deliver the frequency axis in the source frame. To stick to this use, you have to modify the source velocity for each spectrum early in the reduction process with the command `MODIFY VELOCITY` (see associated `HELP` for details). In order to help you, the source systemic velocity of the source provided in the HIFI observing setup by the user is imported into the variable `R%HEAD%HER%VINFO`. If its value is correct, the command

    LAS> MODIFY VELOCITY R%HEAD%HER%VINFO

will shift the frequency axis to the rest frame of this velocity.