The name of the catalogue column to use. If parameter MODE is " ChangeColVals" the name of an existing column must be supplied (a list of available column names is displayed if a non-existent column name is given). If parameter MODE is " AddColumn" the name of the new column must be supplied (an error will be reported if the column already exists).

The name of the catalogue column which gives the first coordinate of each data value. A list of available column names is displayed if a non-existent column name is given. [" RA" ]

The name of the catalogue column which gives the first coordinate of each data value. A list of available column names is displayed if a non-existent column name is given. [" DEC" ]

A descriptive comment to store with the new column if parameter MODE is " AddColumn" . The suggested default is the Label value from the NDF specified by parameter NDF.

Only used if parameter MODE is " Debias" . It gives the type of bias estimator to use when creating the new P and PI values, using the nomeclature of Montier at al " Polarization measurements analysis II. Best estimators of polarization fraction and angle" (A&A, 2018):

• " AS" : The asymptotic estimator. See section 2.3 of Montier et al. This estimator produces bad P and PI values if the squared PI value is less than the variance in PI.

• " MAS" : The modified asymptotic estimator. See section 2.5 of Montier et al. This estimator does not produces bad P and PI values, even if the squared PI value is less than the variance in PI.

• " None" : No de-bising is applied.

The input catalogue.

Determines how the NDF specified by parameter NDF is used to generate the new column values (only used if parameter MODE is " AddColumn" ). If parameter MASKCOL is FALSE (the default), the NDF’ s pixel array is sampled at the positions given in the catalogue columns specified by parameters COL1 and COL2, using the interpolation method specified by parameter METHOD, and the sampled values are stored in the new column. The data type of the new column is set to the data type of the NDF. If parameter MASKCOL is TRUE, the new column holds integer values - 1 if the corresponding pixel in the NDF array is good and 0 otherwise. Parameters COL1 and COL2 again specify the catalogue columns that hold the position for each row. The nearest pixel to the resulting position is tested by comparing it with the appropriate Starlink " bad" value. [FALSE]

Only used if parameter MODE is set to " ChangeColVals" or " AddColumn" . It gives the method to use when sampling the NDF pixel array to generate the new catalogue column values. For details on these schemes, see the descriptions of routines AST_RESAMPLEx in SUN/210. METHOD can take the following values.

• " Bilinear" – The new column values are calculated by bi-linear interpolation among the four nearest pixels values in the input NDF. Produces smoother output NDFs than the nearest-neighbour scheme, but is marginally slower.

• " Nearest" – The new column values are assigned the value of the single nearest input pixel.

• " Sinc" – The new column values are calculated using the sinc(pi$\ast$x) kernel, where x is the pixel offset from the interpolation point and sinc(z)=sin(z)/z. Use of this scheme is not recommended.

• " SincSinc" – Uses the sinc(pi$\ast$x)sinc(k$\ast$pi$\ast$x) kernel. A valuable general-purpose scheme, intermediate in its visual effect between the bilinear and nearest-neighbour schemes.

• " SincCos" – Uses the sinc(pi$\ast$x)cos(k$\ast$pi$\ast$x) kernel. Gives similar results to the " Sincsinc" scheme.

• " SincGauss" – Uses the sinc(pi$\ast$x)exp(-k$\ast$x$\ast$x) kernel. Good results can be obtained by matching the FWHM of the envelope function to the point-spread function of the input data (see Parameter PARAMS).

• " Somb" – Uses the somb(pi$\ast$x) kernel, where x is the pixel offset from the interpolation point and somb(z)=2$\ast$J1(z)/z (J1 is the first-order Bessel function of the first kind. This scheme is similar to the " Sinc" scheme.

• " SombCos" – Uses the somb(pi$\ast$x)cos(k$\ast$pi$\ast$x) kernel. This scheme is similar to the " SincCos" scheme.

• " Gauss" – Uses the exp(-k$\ast$x$\ast$x) kernel. The FWHM of the Gaussian is given by Parameter PARAMS(2), and the point at which to truncate the Gaussian to zero is given by Parameter PARAMS(1).

The initial default is " Nearest" . [current value]

The type of edit to apply. Must be one of the following values:

• " AddColumn" : A new column is added to the catalogue. The name of the new column is given by parameter COL. The values to store in the column are obtained from the NDF specified by parameter NDF in a manner determined by parameter MASKCOL.

• " Debias" : New debiased values are written to the P (percentage polarisation) and PI (polarised intensity) columns based on the values in the Q, U, I and DPI columns. The form of de-biasing to use is specified by parameter DEBIASTYPE. This option is the same as the " Recalc" option except that only the P and PI columns are recalculated.

• " ChangeColVals" : The values in the column specified by parameter COL are changed to the values read from the NDF specified by parameter NDF. The NDF is sampled at the positions stored in the catalogue columns specified by parameters COL1 and COL2, using the interpolation method specified by parameter METHOD.

• " Recalc" : All columns that are derived from the Stokes parameter columns are re-calculated. In other words, the P, PI, ANG, DP, DPI and DANG columns are recalculated on the basis of the curent values in the I, Q, U, DI, DQ and DU columns. The form of de-biasing to use is specified by parameter DEBIASTYPE.

The input NDF to use when parameter MODE is " ChangeColVals" or " AddColumn" .

The output catalogue.

An optional array which consists of additional parameters required by the Sinc, SincSinc, SincCos, SincGauss, Somb, SombCos and Gauss methods (see parameter METHOD).

PARAMS( 1 ) is required by all the above schemes. It is used to specify how many pixels are to contribute to the interpolated result on either side of the interpolation in each dimension. Typically, a value of 2 is appropriate and the minimum allowed value is 1 (i.e. one pixel on each side). A value of zero or fewer indicates that a suitable number of pixels should be calculated automatically. [0]

PARAMS( 2 ) is required only by the Gauss, SombCos, SincSinc, SincCos, and SincGauss schemes. For the SombCos, SincSinc and SincCos schemes, it specifies the number of pixels at which the envelope of the function goes to zero. The minimum value is 1.0, and the run-time default value is 2.0. For the Gauss and SincGauss scheme, it specifies the full-width at half-maximum (FWHM) of the Gaussian envelope measured in output pixels. The minimum value is 0.1, and the run-time default is 1.0. On astronomical NDFs and spectra, good results are often obtained by approximately matching the FWHM of the envelope function, given by PARAMS(2), to the point-spread function of the input data. []

A string giving the units used by the new column if parameter MODE is " AddColumn" . The suggested default is the Units value from the NDF specified by parameter NDF.