AIPS NRAO AIPS HELP file for UVCON in 31DEC19



As of Sun Dec 16 19:43:06 2018


UVCON: Generates UV data for a given array and model

INPUTS

INFILE                             Antenna location file name
IN2FILE                            TSYS and Efficiency
                                   BLANK=>INFILE's data are used
                                   for TSYS and Efficiency
OUTFILE                            Antenna location file name
                                   Positions are in equatorial
                                   coordinate system.
IN2NAME                            Model image name (name)
                                   The both dimensions of the
                                   model must be 2**N pixels
IN2CLASS                           Model image name (class)
IN2SEQ            0.0     9999.0   Model image name (seq. #)
IN2DISK                            Model image disk unit #
INVERS           -1.0    46655.0   CC file version #.
OUTNAME                            Output UV file name (name)
OUTCLASS                           Output UV file name (class)
OUTSEQ           -1.0     9999.0   Output UV file name (seq. #)
OUTDISK           0.0        9.0   Output UV file disk unit #.
NMAPS             0.0     4096.0   No. maps to use for model.
BCOMP                              First CLEAN comp to sub.
                                   1 per field. 0 => 1
NCOMP                              Last CLEAN comp to sub.
                                   to use (0 => all)
FLUX                               Lowest CC component used.
CMETHOD                            Modeling method:
                                   'DFT','GRID'; '    '=>DFT
CMODEL                             Model type: 'COMP','IMAG'
                                   '    ' => 'COMP' => CC components
                                   'IMAG' => image
FACTOR                             Factor times model fluxes.
                                   0 => 1
SMODEL                             Source model, 1=flux,2=x,3=y
                                   See 'explain'.
RASHIFT                            Shift of the model center
                                   relatively of the initial
                                   RA=0, per field (asec)
DECSHIFT                           Shift of the model center
                                   relatively of the initial
                                   declinat., given at APARM(3)
                                   per field (asec)
APARM                              Control information:
                                   1: Frequency of chan. 1, GHz
                                   2: Wavelength of ch 1, cm
                                      IF both .LE. 0 then
                                      wavelength = 0.1 cm
                                   3: Source declination, deg
                                   4: Min hour angle, hours
                                   5: Max hour angle, hours
                                      The hour angles are for
                                      the given array center
                                   6: Min antenna elevation, deg
                                   7: Integration time, sec
                                      0 => 1.D6
                                      to simmulate snapshot
                                   8: Bandwidth(increment) of
                                      the freq. channel, MHz
                                      >=0 => it is increment to
                                      simulate multi chann. data
                                      =0 => Bandwidth = 1MHz
                                      <0 => one channel data to
                                      simulate multi frequency
                                      UV coverage
                                   9: Number of freq. channels
                                      0 => 1
                                  10: Max blockage allowed
                                      0 => 1 -> ANY blockage
BPARM                              Control information:
                                   1: Multiplier of the calcul.
                                      noise. 0 => 1
                                            -1 => 0 (no noise)
                                   2: Atmosphere noise at zenith
                                      in degrees.
                                   3: RMS of pointing error,
                                      random among all antennas
                                      but constant in time,
                                      in arcsec
                                      If (BPARM(3).LT.0) then

                                         the phase and amplitude
                                         errors of each antenna
                                         are simulated instead
                                         of pointing error.
                                         ABS(BPARM(3)) is half
                                         range of homogeneously
                                         distributed phase, rad

                                         BPARM(4) is half
                                         range of homogeneously
                                         distributed natural LOG
                                         of factor to amplitude

                                         BPARM(5):
                                         0 => only one (first)
                                         clean component is
                                         affected by the
                                         phase/amp noise
                                         1 => all clean
                                         components are affected

                                   4: global pointing error,
                                      constant in time for all
                                      antennas,
                                      in arcsec
                                   5: RMS of pointing error,
                                      random among all antennas
                                      and in time,
                                      in arcsec
                                   6: Type of the primary beam
                                      1 => circular dish with
                                           the flat illumination
                                      2 => illumination is 10dB
                                           down at the dish edge
                                      3 => illumination is 15dB
                                           down at the dish edge
                                      The dish diameter is given
                                      at the INFILE (antenna 1)
                                      4 => Gaussian beam with
                                           given BMAJ, BMIN, BPA
                                           in degrees
                                      5 => Gaussian beam with
                                        variable BMAJ, BPA
                                        depending on the time
                                      .GT.0 =>Multiply the model
                                      by the primary beam.
                                      0 => Not multiply the
                                      model by the primary beam.
                                   7: Time tolerance, in minutes
                                      0 => 1
                                      If the difference  of the
                                      current and  previous time
                                      is < the time tolerance,
                                      the pointing error or the
                                      phase of the antenna or
                                      primary beam parameters
                                      are not changed
                                   8: Shift the UV data by
                                      RASHIFT, DECSHIFT?
                                      0 => yes shift
                                      1 => no shift
                                   9: Range of the primary beam
                                      0 => 2.5
                                  10: If OUTFILE.NE.BLANK then
                                      0 => calculate OUTFILE and
                                           exit
                                      1 => calculate OUTFILE and
                                           carry out the rest of
                                           job
CPARM                              Frequencies of the group(IFs)
                                   begins
                                   1: Number of the groups (IFs)
                                   2-10 Frequency of group(IFs)
                                        begins in MHz
BMAJ          0                    FWHM major axis of the
                                   Gaussian primary beam, degree
                                   See help for the variable
                                   primary beam (BPARM(6)=5)
BMIN          0                    FWHM minor axis of the
                                   gaussian primary beam, degree
BPA           0                    Position angle of Gaussian
                                   primary beam, degree
DO3DIMAG                           1 => use W term calculating
                                        visibilities (only if
                                        CMETHOD='DFT', and
                                        CMODEL ='COMP')
                                   0 => no W term calculating
                                        visibilities

HELP SECTION

UVCON
Task:  Generates a UV data file from an array geometry given by
	INFILE. File IN2FILE provides information about elevation
        dependence of antenna efficiency and system noise.
        The visibilities will be computed using a model
	specified by IN2NAME, (either from CC components, or the
	image itself) or from SMODEL.  Gaussian noise will
	be added according to antenna parameters given in the
	INFILE.
Adverbs:
  INFILE.....Name of the user-supplied file defining the array
             configuration and antenna characteristics.
  IN2FILE....Name of the user-supplied file defining the dependence
             of the TSYS and Efficiency of each antenna on elevation.
             These more precise data substitute the TSYS and Efficiency
             of INFILE data. If IN2FILE.EQ.BLANK then INFILE's data are
             used for TSYS and Efficiency
  OUTFILE....Name of the file which have the antenna positions
             given at equatorial coordinate system.
             All other antenna information repeats the INFILE.
  IN2NAME....Model map name (name).      Standard defaults.
             The both dimensions of the model must be 2**N pixels
  IN2CLASS...Model map name (class).     Standard defaults.
  IN2SEQ.....Model map name (seq. #).    0 => highest.
  IN2DISK....Disk drive # of model map.  0 => any.
  INVER......CC file ver. number.          0 => highest.
  OUTNAME....Output UV file name (name).    Standard behavior
             with default 'UV DATA FILE'.
  OUTCLASS...Output UV file name (class).   Standard defaults.
  OUTSEQ.....Output UV file name (seq. #).  0 => highest unique.
  OUTDISK....Disk drive # of output UV file. 0 => highest disk
             with space for the file.
  NMAPS......Number of image files to use for model.  If more than one
             file is to be used, the NAME, CLASS, DISK and SEQ of the
             subsequent image files will be the same as the first file
             except that the LAST 3 or 4 characters of the CLASS will
             be an increasing sequence above that in IN2CLASS.  Thus,
             if INCLASS='ICL005', classes 'ICL005' through 'ICLnnn'
             or 'ICnnnn', where nnn = 5 + NMAPS - 1 will be used.  Old
             names (in which the 4'th character is not a number) are
             also supported: the last two characters are '01' through
             'E7' for fields 2 through 512.  In old names, the highest
             field number allowed is 512; in new names it is 4096.
  BCOMP......The first clean component to process. One value is
             specified for each field used. 0 => 1
  NCOMP......Number of Clean components to use for the model, one
             value per field.  If all values are zero, then all
             components in all fields are used.  If any value is not
             zero, then abs(NCOMP(i)) (or fewer depending on FLUX and
             negativity) components are used for field i, even if
             NCOMP(i) is zero.  If any of the NCOMP is less than 0,
             then components are only used in each field i up to
             abs(NCOMP(i)), FLUX, or the first negative whichever
             comes first.  If abs(NCOMP(i)) is greater than the number
             of components in field i, the actual number is used.  For
             example
                   NCOMP = -1,0
             says to use one component from field one unless it is
             negative or < FLUX and no components from any other
             field.  This would usually not be desirable.
                   NCOMP = -1000000
             says to use all components from each field up to the
             first negative in that field.
                   NCOMP = -200 100 23 0 300 5
             says to use no more than 200 components from field 1, 100
             from field 2, 23 from field 3, 300 from field 5, 5 from
             field 6 and none from any other field.  Fewer are used if
             a negative is encountered or the components go below
             FLUX.
  FLUX.......Only components > FLUX in absolute value are used in the
             model.
  CMETHOD....This determines the method used to compute the
             model visibility values.
             'DFT' uses the direct Fourier transform, this
             method is the most accurate.
             'GRID' does a gridded-FFT interpolation model
             computation.
             '    '  => DFT
             NOTE: data in any sort order may be used by the
             'DFT' method but only 'XY' sorted data may be used
             by the 'GRID' method.
  CMODEL.....This indicates the type of input model; 'COMP' means that
             the input model consists of CLEAN components, 'IMAG'
             indicates that the input model consists of images.
             If CMODEL is '    ' clean components are  used as a model
             If CMODEL is 'IMAG' image is used as a model
             IF pointing error is included (BPARM(6) > 0) then
             CMETHOD and CMODEL are forced to DFT and COMP.
  FACTOR.....This value will be multiplied times the model
             0 => 1. The model are added with the noise.
  SMODEL.....A single component model to be used instead of a CLEAN
             components model; if abs (SMODEL) > 0 then use of this
             model is requested.
                SMODEL(1) = flux density (Jy)
                SMODEL(2) = X offset in sky (arcsec)
                SMODEL(3) = Y offset in sky (arcsec)
                SMODEL(4) = Model type:
                  0 => point model
                  1 => elliptical Gaussian, for which:
                       SMODEL(5) = major axis size (arcsec)
                       SMODEL(6) = minor axis size (arcsec)
                       SMODEL(7) = P. A. of major axis (degrees)
                  3 (not 2 !!!) => uniform sphere, for which:
                       SMODEL(5) = radius (arcsec)
  RASHIFT....Shift of the model center relatively of the initial RA=0
             per field (asec). The RASHIFT is given for the picture
             plane. So the shift at RA is RASHIFT/COS(declination)
             The primary beam points to XREF + RASHIFT(1)
             where XREF is X coordinate value at the reference pixel
  DECSHIFT...Shift of the model center relatively of the initial
             declination, given at APARM(3)
             per field (asec)
             The primary beam points to YREF + DECHIFT(1)
             where YREF is Y coordinate value at the reference pixel
             These shifts can be used for simulation of the multi field
             observation (mosaic)
  APARM......User specified array.
             APARM(1): Frequency of lowest frequency channel, GHz
             APARM(2): Wavelength of longest wavelength channel (cm).
		Only one of these should be specified.
             	(A wavelength of 1 mm is assumed if neither
             	APARM(1) nor APARM(2) is positive.)
             APARM(3): Source declination, deg
             APARM(4): Min hour angle, hours
             APARM(5): Max hour angle, hours
                       The hour angles are for the given array center.
                       The position of the array center (site) is
                       given at the input file.
             APARM(6): Min antenna elevation, deg
             APARM(7): Integration time per visibility point, sec
                       0 => 1.E6. Such a big number should be more
                       of any Hmax-Hmin and therefore the snapshot
                       observation near Hmin will be generated.
             APARM(8): Bandwidth(Increment) of frequency channel, MHz
                       <0 => one channel data are created with different
                             U,V,W for each frequency. Such data are
                             useful for simulating of multi frequency
                             imaging. BANDW=|APARM(8)| is the bandwidth/
                             increment of the channel and is used
                             in UVCON to calculate U,V,W and noise.
                       >=0 =>it is frequency increment and the created
                             UV data are AIPS' standard multi channel
                             data. The data can be used for different
                             transformations in AIPS. In particular
                             such data can be used for simulating of
                             smearing effect using AIPS tasks UVAVG
                             for time averaging and AVSPC or SPLAT
                             for frequency averaging.
                             =0 => BANDW = 1MHz
             APARM(9): Number of freq. channels to simulate different
                       U, V, W using different frequencies. 0 => 1
                       The frequency of channel 'i' is determined by:
                       FREQ(i) = APARM(1) + (i-1)*APARM(8), i=1,2..APARM(9)
             APARM(10): Max fractional area blockage of one antenna by
                        any other.
                       0 => 1. Maximum possible blockage is 1
                               (the total blockage). Therefore the
                               default (1) allows any blockage.
  BPARM......User specified array.
             BPARM(1): Multiplication factor for the noise. 0 => 1
                       -1 = > 0 (no noise)
             BPARM(2): Atmosphere noise at zenith, in degrees.
                       It is used for calculation visibilities noise and
                       weights depending on elevation
             BPARM(3): RMS of pointing error, random among all antennas
                       but constant in time, in arcsec
             BPARM(4): global pointing error, constant in time for all
                       antennas, in arcsec. This error simulates
                       the possible error of the source coordinates
             BPARM(5): RMS of pointing error, random among all antennas
                       and in time, in arcsec

             The total pointing error for the given antenna and time is
             equal to:
             BPARM(3) + BPARM(4) + BPARM(5)
             The pointing error simulation is carried out if the total
             pointing error exceeds 0.00001

             If BPARM(3) is negative  then
                the phase and amplitude errors of each antenna
                are simulated instead of pointing error.
                ABS(BPARM(3)) is half range of homogeneously
                distributed phase, in radians
                BPARM(4) is half range of homogeneously
                distributed natural logarithm of factor to amplitude.
                BPARM(5):
                0 => only one (the first) clean component of the model
                is affected by the phase/amp noise
                1 => all clean components of the model are affected.

             The pointing as well as phase and amplitude error simulation
             is carried out only if CMETHOD='DFT' and CMODEL='COMP'
             If not then CMETHOD and CMODEL are forced to have these
             values.
             BPARM(6): Type of the primary beam
                       1 => circular dish with the flat illumination;
                            close to the VLA antenna
                       2 => illumination goes 10dB down at the dish
                            edge
                       3 => illumination goes 15dB down at the dish
                            edge
                            The antenna diameter and the wavelength
                            are picked up from the input file and from
                            APARM(1)/APARM(2)
                       2,3 may correspond to the future ALMA antenna
                       4 => Gaussian beam with given BMAJ, BMIN, BPA
                            in degrees
                       5 => Gaussian beam with variable BMAJ, BMIN, BPA
                            depending on the time.
                            BMIN stays constant at this case.
                            BMAJ and BPA are calculated for each time at
                            this case. The primary beam can be variable,
                            if the array element is another array (antenna
                            station). In this case the projection of
                            the antenna station aperture on the source
                            picture plane will be changed depending on
                            the source elevation. So if the beam of the
                            antenna station is circular two dimensional
                            Gaussian at zenith, then it will be elliptical
                            two dimensional Gaussian with the major axis
                            increased at 1/sin(el) times. UVCON calculates
                            elevation and azimuth for each visibility(time)
                            and recalculates BMAJ in BMIN/SIN(EL).
                            BMIN stays without change. The new Gaussian
                            beam is rotated to direct the BMAJ in the
                            calculated azimuth.

                            The variable primary beam simulation
                            is carried out only if CMETHOD='DFT' and
                            CMODEL='COMP'
                            If not then CMETHOD and CMODEL are forced to
                            have these values.
                       0 => 1
             BPARM(7): Time tolerance, in minutes; 0 => 1.
                       If the difference  of the current and  previous
                       times is less than the time tolerance,
                       the pointing error or the phase/ampl of the
                       given antenna, or  primary beam parameters
                       are not changed.
                       By other words: the change of the parameters  is
                       carried out every BPARM(7) minutes.
             BPARM(8): 0 => the UV data are shifted by RASHIFT, DECSHIFT
                            simulating the mosaic observation at the
                            pointing given by RASHIFT, DECSHIFT
                       1 => the UV data are not shifted by RASHIFT,
                            DECSHIFT. The model image is multiplied by
                            the primary beam pointed at the direction
                            given by RASHIFT, DECSHIFT, but the tangent
                            stays at the given (RA=0, DEC=APARM(3)).
                            This simulates the pseudo mosaic observation.
             BPARM(9): Range of the primary beam (in one direction)
                       0 => 2.5
                       The argument of the function describing the PB
                       is PI*RANGE
                       For the circular dish with flat illumination
                       the first null occurs when the range = 1.2.
                       The program calculates the beam inside of the
                       range and put it to zero outside.
                       Gaussian presentation of the beam corresponds to
                       the function exp(-4ln2*ARG)
                       ARG = (x/bmaj)^2 + (y/bmin)^2
                       So x=bmaj/2, y=0 gives PRBEAM=0.5
                       The value ARG=2.5 gives PRBEAM = 2^(-10) ~1E-3
             BPARM(10):If OUTFILE.NE.BLANK then
                          0 => calculate OUTFILE and exit
                          1 => calculate OUTFILE and carry out the rest
                               of job
  CPARM......Frequencies of group(IF) begin
             CPARM(1): Number of the groups (IFs)
             CPARM(2-10): Frequency of the group(IF) begins, in MHz
             IF (CPARM(1).NE.0) THEN:
                The total number of frequencies is CPARM(1)*APARM(9)
                The frequency values are calculated as:
                   CPARM(IFRGR+1) + (IFRCHA - 1) * APARM(8)
                where
	           IFRGR group(IF) number
                   IFRCHA channel number at each group
  BMAJ.......FWHM major axis of the Gaussian primary beam at the level
             0.5, degree.
  BMIN.......FWHM minor axis of the Gaussian primary beam at the level
             0.5, degree. BMIN should be given  at the case of the time
             variable primary beam.
  BPA........Position angle of the Gaussian primary beam, degree
             BMIN stays constant when the time variable primary beam is
             simulated (BPARM(6)=5).
             BMAJ and BPA are calculated for each time at this case.
  DO3DIMAG...1 => use W term calculating visibilities. Can be used
                  for investigation of the wide field of view problem.
                  Can be used only if CMETHOD='DFT', and CMODEL ='COMP'
             0 => no use W term calculating visibilities

EXPLAIN SECTION

UVCON: Task to create UV data corresponding to the given source
       model with noise.
PROGRAMMER: L. Kogan, NRAO, Socorro.
DOCUMENTOR: R. Perley, NRAO, Socorro.
RELATED PROGRAMS: UVSIM, UVSUB, UVMOD

                          PURPOSE

     This task is used to generate a u-v database for
an interferometric array whose configuration is
specified by the user. Visibilities corresponding to a
specified model, and Gaussian noise appropriate for the
specified antenna characteristics are calculated for each visibility.
The output is a standard AIPS u-v data file. This task replaces
the old procedure which required use of the AIPS tasks UVSIM,
UVSUM, UVMOD and verb PUTHEAD. The array geometry can be
specified in four different coordinate systems: earth-centered
equatorial, local tangent plane, geodetic, and array-centered
equatorial.  (See definitions below).


               SPECIFYING THE ARRAY CONFIGURATION

     The information defining the array configuration and
antenna characteristics is read by UVCON from an auxiliary input file,
supplied by the user.  This is a free-format text file.  One must list,
in the following order:

Line 1: The number of antennas,
Line 2: The site latitude(geodetic), the site longitude, in degrees,
        The site height relatively the geoid, in meters.
Line 3: A multiplicative conversion factor specifying how the
        antenna coordinates, listed next by the user, can be
        converted into units of meters; and a second
        multiplicative conversion factor specifying how the listed
        antenna diameters can be converted into units of meters.
	If the antenna location coordinates are given in nanoseconds,
	the conversion factor is 0.299.

	The remaining lines specify the antenna location and parameters,
	with one line for each antenna.  Each line is formatted thus:

Col. 1:	The coordinate system:  All are right-handed.  Units are in
	meters, (but see note for Line 3, above).
	   0 => Equatorial, with X positive towards
		Greenwich longitude (and latitude = 0), Y to the
		'east', and Z to the North Pole.
		Units in meters, but see Line 3 description above.
                Warning: VLBA uses opposite direction for Y axis,
                so you need to change it if you use it.
	   1 => Local Horizon, with X positive towards east,
		Y positive towards north, Z positive to local zenith.
		Units in meters, but see Line 3 description above.
		Coordinate origin is at the array center.
	   2 => Geodetic, with coordinates given by geodetic latitude,
		longitude (positive towards west), (both in degrees)
		and elevation above the geoid (in meters).
	   3 => Array Centered Equatorial.  The same as '0' but
		with X positive to Dec = 0 on local meridian,
		Y positive to east, and Z positive towards NCP.
                This option is good for VLA
		Units in meters, but see Line 3 description above.

Col. 2:	Antenna Coordinate X, as defined above.
Col. 3: Antenna Coordinate Y, as defined above.
Col. 4: Antenna Coordinate Z, as defined above.
Col. 5: Antenna diameter (meters, but see note for Line 3, above).
Col. 6: Antenna efficiency (fraction). 0 => 0.5
Col. 7: Antenna system temperature (K) 0 => 50K
Col. 8: Number of levels of digitization of signals. 0 => 2 level
Col. 9: Put one if the coordinates are given relatively the Earth's
        center (VLBI case); Put zero in other cases.

The antenna diameters, efficiency, noise temperature, and number of
levels in the digitizer are used to calculate the noise level for the
given visibility. This noise can be multiplied by the factor
(BPARM(1)).  The factor is 1 (the noise is equal to the calculated
one) if BPARM(1) = 0 or 1.  Set BPARM(1)=-1 for the noise calculation
to be turned off. Dependence of the antenna efficiency and noise
temperature on elevation is given at file IN2FILE.
Comment line can be added at both INFILE and IN2FILE putting semi column
(';') at the first position of the line.

Here is a sample file for a six-element array:

6
30 20
1 1
   3  499.8614     -1317.9860    -735.2027    10   0.6   50   4
   1 -801.3750      -124.9699    1182.1318    20   0.4   50   2
   3 -5271.2720     -823.5634    7791.9982    30   0.4   50   2
   3   152.7899     -401.2680    -223.3888    40   0.4   60   3
   3 -6870.8985    -1072.9210   10148.7829    50   0.4   50   2
   3   765.2380     2889.4558   -1108.8724    60   0.4   50   2

The array center is at latitude 30 degrees and longitude 20 degrees to
west.  Conversion factors for both antennas positions and diameters
equal 1, so the relevant values are given in meters.  Position of the
second antenna is given in the local RH system with Z as local zenith.
All other antennas' positions are given in a local equatorial
coordinate system.  Diameters of the antennas are 10, 20, 30, 40, 50,
and 60 meters. The efficiency of the first antenna is 0.6. All other
antennas have an efficiency of 0.4.  The noise temperature of the
fourth antenna is 60 degrees. All other antennas have the noise
temperature 50 degrees. The first antenna has four level digitizer
(two bits), the fourth one a three level digitizer, and the all other
antennas have two level digitizer (1 bit).


One must supply the name of the input file via the AIPS
adverb INFILE.  Examples:
         INFILE='myarea:test.ant'                 (Unix)
            where MYAREA is an environment variable set before
            starting AIPS.  For example:
             percentsetenv MYAREA /mnt/myarea/sim (in csh)
            $export MYAREA=/mnt/myarea/sim (in ksh)

There are five ready input files for 4 VLA configurations and VLBA.
The five files are under $AIPSTARS and should be called as:

INFILE 'AIPSTARS:VLA-A_UVCON'
INFILE 'AIPSTARS:VLA-B_UVCON'
INFILE 'AIPSTARS:VLA-C_UVCON'
INFILE 'AIPSTARS:VLA-D_UVCON'
INFILE 'AIPSTARS:VLBA_UVCON'

If a user want to change the data of VLA, VLBA configuration, he/she can
copy the relevant file(s) to his area, edit it and create his own version.



           SPECIFYING THE DEPENDENCE of the TSYS and EFFICIENCY
                        on the ELEVATION (IN2FILE)

     The information defining the antenna noise temperature (TSYS) and
efficiency dependence on elevation is read by UVCON from an auxiliary
second input file (IN2FILE), supplied by the user.
This is a free-format text file, including the four columns.

Col.1:  Antenna number
Col.2:  Elevation in degrees.
Col.3:  TSYS in degrees K
Col.4:  Efficiency, undimensional.

UVCON calculates elevation for the given antenna and evaluates the noise
temperature and efficiency interpolating the IN2FILE's data to the given
elevation for the given antenna.

If IN2FILE .EQ. BLANK  or there are no data for an antenna then TSYS and
efficiency of the antennas are considered independent on elevation and are
picked up from the INFILE.
Contribution of the sky noise (at this case) is added depending on
elevation (COSEC(ELEV)) considering the zenith atmosphere is identical for
all antennas.

Here is an example of I2FILE:

Here is a sample file for a six-element array:

    1    15.0   70    0.3
    2    20.0   65    0.35
    3    20.0   65    0.35
    4    20.0   65    0.35
    1    25.0   60    0.4
    2    30.0   52    0.45
    3    30.0   50    0.45
    4    30.0   50    0.45
    1    40.0   40    0.5
    2    45.0   45    0.55
    3    45.0   45    0.55
    4    45.0   45    0.55
    1    45.0   40    0.6
    2    50.0   35    0.65
    3    50.0   35    0.65
    4    50.0   35    0.65

If the data for an antenna absent in the file I2FILE then INFILE's
data used to calculate noise and efficiency for this antenna.

   USING UVCON TO SIMULATE EFFECT OF SMEARING AS A RESULT OF AVERAGING
                     IN TIME AND/OR FREQUENCY

UVCON prepares the AIPS' standard multi channel UV data for the given set
of times and frequencies.
Having simulated such UV data the user can simulate the smearing effect
using the AIPS tasks UVAVG (time averaging) and AVSPC, SPLAT
(frequency averaging).
Use APARM(8)>=0 in this case.

   USING UVCON TO SIMULATE UV DATA FOR THE MULTI FREQUENCY SYNTHESIS.

APARM(8) should be negative at this case. UVCON creates the one channel UV
data with different U,V,W for each of APARM(9) frequencies which are
incremented by |APARM(8)|. Such data can be immediately read for an imaging
task (AIPS' task IMAGR for example) to create image based on the multi
frequency observations (multi frequency synthesis).


















AIPS