!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!! Copyright 2011 California Institute of Technology
!!!
!!! fix_reference.class
!!!
!!! 2011-06-03 version 1.0 Initial release
!!! 2014-11-17 version 2.0 sradford
!!!   update for changes in class variable names 
!!!
!!! @fix_reference [ new_restf(MHz) [ new_voff(km/s) ] ]
!!!
!!! Fixes reference channel and frequency and velocity offset.
!!!
!!! Supply a correct frequency in the signal sideband that was doppler-tracked,
!!! and optionally a correct velocity offset to avoid a round-off error.
!!!
!!! Use case: You have observed 12CO and 13CO lines simultaneously with
!!! wideband receiver and spectrometer by doppler-tracking the 12CO frequency.
!!! The center of the spectrometer was offset from the 12CO frequency to
!!! accommodate the 13CO line.  Now you want to fix the header variables so
!!! that those values are for the 12CO frequency in the signal sideband.
!!!
!!! file in ...
!!! file out ...
!!! find ...
!!! set variable spectro write
!!! for i 1 to found
!!! get next
!!! @fix_reference 220398.6765 0
!!! write
!!! next
!!!
!!! C18O (J=2-1) 219560.3568 MHz
!!! 13CO (J=2-1) 220398.6765 MHz
!!! 12CO (J=2-1) 230538.0000 MHz

sic\let clight = 2.99792458e5 /new double ! Speed of light (km/s)

sic\let new_restf = r%head%spe%restf /new double
sic\let new_image = r%head%spe%image /new double
sic\let new_rchan = r%head%spe%rchan /new real
sic\let new_fres = r%head%spe%fres /new real ! No change (topocentric!!!)
sic\let new_vres = r%head%spe%vres /new real
sic\let new_voff = r%head%spe%voff /new real

sic\if ("&1 ".ne." ") then
       sic\let new_restf = &1
       sic\let new_image = (r%head%spe%restf+r%head%spe%image)-new_restf
       sic\let new_rchan = r%head%spe%rchan+(new_restf-r%head%spe%restf)*(1+r%head%spe%doppler)/new_fres
       sic\let new_vres = -clight*new_fres/((1+r%head%spe%doppler)*new_restf)
       sic\let new_voff = r%head%spe%voff-clight*(new_restf-r%head%spe%restf)/r%head%spe%restf

       sic\if ("&2 ".ne." ") then
              sic\let new_voff = &2
       sic\end if

       sic\let r%head%spe%restf = new_restf
       sic\let r%head%spe%image = new_image
       sic\let r%head%spe%rchan = new_rchan
       sic\let r%head%spe%fres = new_fres
       sic\let r%head%spe%vres = new_vres
       sic\let r%head%spe%voff = new_voff
sic\end if