CALIBRATE

             OBS\CALIBRATE [SKY|COLD|WVR|ATTENUATORS]

         - Starts an atmospheric amplitude calibration.  The calibration  is
    done  by measurements on the absorber, on the sky, and optionally on the
    internal cold load when argument COLD is given, by moving  the  receiver
    tables  and  mirrors.   An  extra  attenuation  can  be  inserted in the
    receiver 1 when measuring the power on the absorber; this attenuation is
    specified  by  command OBS\SET ATTENUATION.  The calibration mode can be
    specified by the OBS\SET CALIBRATION command.

         In INTERferometric mode, the total power Detectors are  used.   The
    spectral correlator is always tweaked in this procedure.

         This command is not available in OPTICAL or TEST modes.

         - With argument SKY, only the  sky  will  be  measured,  unless  no
    ambient  load  (absorber)  measurement  has been obtained recently (i.e.
    during the last calibration  interval,  of  duration  specified  by  SET
    CALIBRATION  INTERVAL);  in  that  case  the  command  is  executed like
    CALIBRATE with no argument, and a new calibration interval is started.

         - With argument WVR, a specific sequence is performed to  calibrate
    the   22GHz   Water   Vapour   Radiometers.   The   correlators  run  an
    autocorrelation while the 22GHz radiometers measure  their  own  ambient
    load  and  noise  tubes.  The  actual observing sequence is given in the
    command line as a  list  of  observing  times  (in  seconds)  and  codes
    ('OFF','NOISE', or 'LOAD'). The default sequence is given by:

         CALIBRATE WVR 4 OFF 4 NOISE 4 OFF