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        CLIC\MONITOR delta_time

    This  command  is used to prepare the atmospheric phase correction based
    on the total power monitor (normally done at 1.3  mm).  It  process  all
    scans in the current index and performs two operations.

    First, it processes the calibration scans to compute the correction fac-
    tors. i.e. the change of path length for a given change in emission tem-
    perature of the atmosphere at the atmospheric monitor frequency (normal-
    ly 1.3 mm, i.e. using Receiver 2 data).  These  correction  factors  are
    then written in subsequent scans, until a new calibration is found.

    Second, the scans in the current index are grouped in intervals of maxi-
    mum 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 correc-
    tion 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-atmo-
    spheric  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 ze-
    ro in one scan: the average phase is not changed, only the coherence  is
    restored  leading  to an improved amplitude (this is what is done in the
    correlator at the Plateau de Bure to compute the scan-averaged  spectral
    and continuum quantities).

Gildas manager 2022-01-17