UV_TRACK_PHASE

    UV_TRACK_PHASE  simulates the uv coverage of an observation specified by
    the source, observatory, and hour angle range. The output is a uv  table
    that  can be used as input for tasks such as UV_FMODEL. Caution: this uv
    table is not standard, as it includes two addition columns (#11 with el-
    evation, #12 with integration time).

    The  weight  column  (#10) is filled with as realistic as possible esti-
    mates of the actual weights (derived from Trec, Tau, elevation).

    The visibilities columns (#8 and #9) are filled with a point source (am-
    plitude  =  1,  phase = 0). Random phase noise can be added, to simulate
    atmospheric phase noise.

    If DO_SCREEN = YES, a phase screen is used to simulate phase noise: this
    file  contains a statistically correct spatial distribution of the phase
    perturbation induced by the atmopshere. This screen moves above the  ar-
    ray  at  the wind velocity. The correct phase value is computed each an-
    tenna at each time dump.

    If DO_CALIB = YES, the observations of a calibrator are  simulated,  as-
    suming  a loop calibrator-source-calibrator-source. The corresponding uv
    table is created.

    If DO_RADIOM = YES, a phase correction based on WVR measurements is sim-
    ulated.

    UV_TRACK family of tasks (in order of increasing complexity):

        - UV_TRACK: uv coverage + random phase noise
        - UV_TRACK_PHASE: phase noise from atmospheric screen + observations
          of calibrator +  WVR correction
        - UV_OBSERVE: also includes amplitude noise
        - UV_OBSERVE_NEW: also includes anomalous refraction