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Workspace Method sensor_responseFillFgrid

Description

Polynomial frequency interpolation of spectra.

The sensor response methods treat the spectra to be piece-wise linear
functions. This method is a workaround for making methods handling
the spectra in a more elaborate way: it generates spectra on a more
dense grid by polynomial interpolation. The interpolation is not
done explicitly, it is incorporated into sensor_response.

This method should in general increase the calculation accuracy for
a given f_grid. However, the selection of (original) grid points
becomes more sensitive when using this method. A poor choice of grid
points can result in a decreased accuracy, or generation of negative
radiances. Test calculations indicated that the error easily can
increase with this method close the edge of f_grid, and it could
be wise to make f_grid a bit wider than actually necessary to avoid
this effect

The method shall be inserted before the antenna stage. That is, this
method shall normally be called directly after sensor_responseInit.

Between each neighbouring points of f_grid, this method adds
*nfill* grid points. The polynomial order of the interpolation is
*polyorder*.

Authors: Patrick Eriksson

Synopsis

sensor_responseFillFgrid(

sensor_response, sensor_response_f, sensor_response_pol, sensor_response_dlos, sensor_response_f_grid, sensor_response_pol_grid, sensor_response_dlos_grid, polyorder, nfill )

Variables

OUT+IN	sensor_response	(Sparse)	The matrix modelling the total sensor response.
OUT+IN	sensor_response_f	(Vector)	The frequencies associated with the output of sensor_response.
OUT+IN	sensor_response_pol	(ArrayOfIndex)	The polarisation states associated with the output of sensor_response.
OUT+IN	sensor_response_dlos	(Matrix)	The relative zenith and azimuth angles associated with the output of sensor_response.
OUT+IN	sensor_response_f_grid	(Vector)	The frequency grid associated with sensor_response.
IN	sensor_response_pol_grid	(ArrayOfIndex)	The "polarisation grid" associated with sensor_response.
IN	sensor_response_dlos_grid	(Matrix)	The zenith and azimuth angles associated with sensor_response.
GIN	polyorder	(Index, Default: 3)	Polynomial order of interpolation
GIN	nfill	(Index, Default: 2)	Number of points to insert in each gap of f_grid