1 UV_OBSERVE Compute uv coverage + phase noise + amplitude errors UV_OBSERVE 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 eleva- tion, #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. 1 ENDOFHELP