MONITOR

 

        CLIC\MONITOR delta_time

    This command is  used  to  prepare  the  atmospheric  radiometric  phase
    correction.    It   processes  the  calibration  scans  to  compute  the
    correction factors (i.e.  the change of path length for a  given  change
    in  emission  temperature  of  the atmosphere at the atmospheric monitor
    frequency (normally 1.3 mm).

    The scans in the current index  are  grouped  in  intervals  of  maximum
    duration  `delta_time' (in seconds); source changes will also be used to
    separate intervals. In each interval a straight line is  fitted  in  the
    variation  of atmospheric emission as a function of time; this line will
    be  the  reference  value  for  the  atmospheric  correction,  i.e.  the
    correction  at  time  t  is  proportional  to the difference between the
    atmospheric emission at time t and the reference at time t.  This scheme
    is used to avoid contaminating the correction with total power drifts of
    non-atmospheric origin (changes in receiver noise and gain, and  changes
    in ground noise).

    MONITOR 0 will use for each scan the average of the atmospheric emission
    as  the  reference  value.  This will cause the correction to average to
    zero in one scan: the average phase is not changed, only  the  coherence
    is restored leading to an improved amplitude.