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This task simulates observations performed with single-dish antennas, to
be used later on as short spacings information. The model image is con-
volved by the antenna lobe (via Fourier Transform) and the intensity is
then estimated at (i) the position of the mosaic fields, and (ii) on an
externally defined grid (see IMAGE_SAMPLING documentation). If the re-
quired position does not coincide with a pixel center, a bilinear inter-
polation from the neighbor pixels is performed.
Pointing errors can be simulated by estimating the intensity at a
slightly wrong position. This task can generate simple kind of pointing
errors but it can also read an input pointing error table (enabling to
simulate much more complex kind of pointing errors).
Thermal noise can then be added to the data, and the corresponding
weight is stored. Finally, a calibration error can be simulated: the ob-
served intensities are multiplied by a random factor whose mean value
(different from 1 if a systematic error is present) and rms can be spec-
ified. In this case, we obtain: results = cal_rr*(model+thermal0ise).
The error on the amplitude gain is modeled as the sum of an offset and a
drift with time. The offset and drift values are randomly reset at each
calibration for each antennas. In addition, an offset common to all the
antennas can also be added to the amplitude gain.
Intensity unit of input image is supposed to be Kelvin. The output table
has the following format: 4 columns x Number of antenna x (NFIELDS$ +
Number of observed positions). Column 1 is the X offset in radian, col-
umn 2 the Y offset in radian, column 3 the weight and column 4 the flux
in Jy. The first NFIELDS$ lines of the model are the position of the
mosaic for use by UV_ZERO and all the other ones are the nod of the ex-
ternally defined grid (by IMAGE_SAMPLING) for use by UV_SINGLE. This
complex line layout comes from historical reasons (as usual)...
Limitation: only image can be processed (i.e. *no* data cube) meaning
that this task can not (yet) handle spectra cubes.