MODIFY DOPPLER

        LAS\MODIFY DOPPLER [SIGN|*|Value]

    Change the Doppler factor according to the CLASS convention (-V/c). With
    no  argument,  checks  whether  the  header value is consistent with the
    CLASS value computed according to the date and observatory. The checking
    precision  corresponds  to  0.6  m/s  in  V.  A  logical  SIC  variable,
    DOPPLER_PB, is set to true if the values disagree.  If  an  argument  is
    present:

      SIGN   change the sign of the Doppler factor but do not recompute it,
      *      compute  and update the Doppler factor according to the observ-
             ing date-time and the observatory position (this  position  can
             be customized with SET OBSERVATORY),
      Value  set the Doppler factor to <Value>