1 UV_OBSERVE_NEW Compute uv coverage + phase/amplitude errors + anomalous refraction

    UV_OBSERVE_NEW  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). Amplitude calibration errors (offset + drifts)
    can be included. Random phase noise can be added, to simulate atmospher-
    ic 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


2 DECLINATION$
        TASK\REAL "Source declination" DECLINATION$

    Declination of the source (degrees).

2 FREQUENCY$
        TASK\REAL "Line frequency" FREQUENCY$

    Observing frequency (GHz).

2 NEW$
        TASK\LOGICAL "New or Old table" NEW$

    Create new uv table or append to existing table.

2 UV_TABLE$
        TASK\CHARACTER "Table name" UV_TABLE$

    Output uv table name.

2 STATION_FILE$
        TASK\CHARACTER "Station file name" STATION_FILE$

    Input file with antenna position (stations).

2 UV_SPACING$
        TASK\REAL "UV spacing" UV_SPACING$

    Sampling in uv plane (should be antenna diameter/2), used to compute in-
    tegration time if INTEGRATION.ne.0.

2 DIAMETER$
        TASK\REAL "Antenna diameter" DIAMETER$

    Antenna diameter (m). Used to detect shadowing.

2 HORIZON$
        TASK\REAL "Minimum elevation" HORIZON$

    Minimum elevation of the source.

2 LATITUDE$
        TASK\REAL "Observatory latitude" LATITUDE$

    Latitude of the observatory.

2 HOUR$
        TASK\REAL "Hour angle range" HOUR$[2]

    Hour angle range of the observations; only the time range where the ele-
    vation is larger than the specified minimum elevation  will  be  consid-
    ered.

2 INTEGRATION$
        TASK\REAL "Integration time" INTEGRATION$

    Integration time of each dump (sec).

2 BANDWIDTH$
        TASK\REAL "Bandwidth" BANDWIDTH$

    Bandwidth (MHz). Used to compute weigths.

2 TREC$
        TASK\REAL "Receiver temperature" TREC$

    Receiver temperature (K). Used to compute Tsys and weights.

2 TAU$
        TASK\REAL "Zenith opacity" TAU$

    Zenith opacity. Used to compute Tsys and weights.

2 PHASE$
        TASK\REAL "Phase noise" PHASE$

    Phase  noise rms (degrees). The phase noise will be random with a gauss-
    ian distribution. Used only if DO_SCREEN = NO.

2 DO_SCREEN$
        TASK\LOGICAL "Use phase screen?" DO_SCREEN$

    Use or not the phase screen to estimate the atmospheric phase noise.

2 PHASE_SCREEN$
        TASK\CHARACTER "Phase screen file" PHASE_SCREEN$

    Input phase screen file.

2 PHASE_NOISE$
        TASK\REAL "Phase noise at 300 m" PHASE_NOISE$

    This is used to scale the phase screen values.

2 WINDANGLE$
        TASK\REAL "Wind position angle (deg)" WINDANGLE$

    Position angle of the wind direction (deg).

2 WINDVELO$
        TASK\REAL "Wind velocity (m/s)" WINDVELO$

    Wind velocity (m/s).

2 DO_CALIB$
        TASK\LOGICAL "Create calibrator table?" DO_CALIB$

    Simulate or not the observation of a phase calibrator.

2 CAL_UV_TABLE$
        TASK\CHARACTER "Calibrator uv table" CAL_UV_TABLE$

    Output uv table for the calibrator observations.

2 DEADTIME$
        TASK\REAL "Dead time (sec)" DEADTIME$

    Dead time between source and calibrator observations (sec).

2 CAL_INTEG$
        TASK\REAL "Calib. integ. time (dumps)" CAL_INTEG$

    Integration time on calibrator (in unit of dump, i.e.  INTEGRATION).

2 SOURCE_INTEG$
        TASK\REAL "Source integ. time (dumps)" SOURCE_INTEG$

    Integration time on source (in unit of dump, i.e.  INTEGRATION).

2 CAL_DIST$
        TASK\REAL "Angular distance of calib. (deg)" CAL_DIST$

    Angular distance between the source and the calibrator (deg).

2 CAL_ANGLE$
        TASK\REAL "Position angle calib. direction" CAL_ANGLE$

    Position angle of the source-calibrator direction (deg).

2 ALTITUDE$
        TASK\REAL "Phase screen altitude" ALTITUDE$

    Phase screen altitude (m). Used to compute the linear  distance  between
    the source and calibrator directions at the phase screen level.

2 DO_RADIOM$
        TASK\LOGICAL "Apply WVR ?" DO_RADIOM$

    Apply or not atmospheric phase correction from WVR measurements.

2 WVR_PRECIS$
        TASK\REAL "WVR Precision" WVR_PRECIS$

    WVR  precision.  The  corrected  phase is modelled by: Pcorr(t) = P(0) +
    Precision * (P(t)-P(0)) + Noise

    Hence, precision = 0 means a perfect radiometer; precision = 1 means  no
    correction.

2 WVR_NOISE$
        TASK\REAL "WVR Noise" WVR_NOISE$

    WVR noise rms (random, gaussian distribution).

2 DO_CORRECT$
        TASK\LOGICAL "Apply Calibrator Phase " DO_CORRECT$

    Phase  referencing (or not) to the last measurement on calibrator.  Used
    only if DO_RADIOM = YES.

2 AMPLITUDE$[2]
        TASK\REAL "Amplitude error and drift" AMPLITUDE$[2]

    Amplitude errors: offset (in %) and drift (in %/hour).  These  are  rms,
    actual values are computed for each antenna.

2 AMP_TIME$
        TASK\REAL "Time between amplitude calibration" AMP_TIME$

    Time  between  "calibration  amplitude",  eg pointing measurements.  The
    offset of the amplitude error is recomputed.

2 DO_ANREFR$
        TASK\LOGICAL "Compute anomalous refraction?" DO1

    Compute or not the anomalous refraction (pointing errors).  The  RA  and
    DEC  terms are written in the column #13 and #14 of the output uv table.
    Note: this may introduce some trouble if this table is  processed  as  a
    normal uv table (e.g. using uv_map).


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