### AST2NDF

Converts an Asterix data cube into a simple NDF

#### Description:

This application converts an Asterix data cube into a standard NDF. See Section "Notes" (below) for details of the conversion.

ast2ndf in out

#### Parameters:

The name of the input Asterix data cube. The file extension (.sdf) should not be included since it is appended automatically by the application.
##### OUT = NDF (Write)
The name of the output NDF containing the data cube written by the application. The file extension (.sdf) should not be included since it is appended automatically by the application.

#### Examples:

ast2ndf ast_cube ndf_cube
This example generates NDF data cube ndf_cube (in file ndf_cube.sdf) from Asterix cube ast_cube (in file ast_cube.sdf).

#### Notes:

This application accepts data in the format used by the Asterix package (see SUN/98). These data are cubes, with two axes comprising a regular grid of positions on the sky and the third corresponding to energy or wavelength. The data are Starlink HDS files which are very similar in format to a standard NDF. The following points apply.
• The Asterix QUALITY array is non-standard. There is no QUALITY component in the output NDF. Instead ‘bad’ or ‘null’ values are used to indicate missing or suspect values.

• The VARIANCE component is copied if it is present.

• The non-standard Asterix axis components are replaced with standard ones.

• The order of the axes is rearranged.

#### References

D.J. Allan and R.J. Vallance, 1995, in SUN/98: ASTERIX – X-ray Data Processing System, Starlink.

Kappa: AXCONV.