NAME

Astro::FITS::HdrTrans - Translate FITS headers to standardised form

SYNOPSIS

  use Astro::FITS::HdrTrans qw/ translate_from_FITS
                                translate_to_FITS /;

  %generic_headers = translate_from_FITS(\%FITS_headers);

  %FITS_headers = translate_to_FITS(\%generic_headers);

  @headers = Astro::FITS::HdrTrans->generic_headers();
  @classes = Astro::FITS::HdrTrans->translation_classes();

DESCRIPTION

Converts information contained in instrument-specific FITS headers to and from generic headers. A list of generic headers are given at the end of the module documentation.

CLASS METHODS

Some class methods are available

generic_headers

Returns a list of all the generic headers that can in principal be used for header translation. Note that not all the instruments support all the headers.

 @hdrs = Astro::FITS::HdrTrans->generic_headers();

translation_classes

Return the names of all the translation classes that will be tried when translating a FITS header.

 @classes = Astro::FITS::HdrTrans->translation_classes();

If arguments are supplied, the list of translation classes is set to the supplied values.

 Astro::FITS::HdrTrans->translation_classes( @new );

reset_translation_classes

Revert back to the reference list of translation classes.

  Astro::FITS::HdrTrans->reset_translation_classes;

Useful if the list has been modified for a specific translation.

push_class

Allows additional classes to be pushed on the list of valid translation classes.

  Astro::FITS::HdrTrans->push_class( $class );

The class[es] can be specified either as a list or a reference to an array.

FUNCTIONS

The following functions are available. They can be exported but are not exported by default.

translate_from_FITS

Converts a hash containing instrument-specific FITS headers into a hash containing generic headers.

  %generic_headers = translate_from_FITS(\%FITS_headers,
                                         class => \@classes,
                                         prefix => 'ORAC_',
                                        );

This method takes a reference to a hash containing untranslated headers, and a hash reference containing the following optional keys:

• class - A reference to a list of subclasses to try to use for header translations. This list overrides the default list. If left blank, the default list will be used, as returned by the translation_classes method. This is sometimes required to break degeneracy when you know you have a limited set of valid instruments.

• prefix - A string prefix to add to the front of every translated header name. For example, if this prefix is set to 'ORAC_', then the translated header for the instrument value, whose key is normally 'INSTRUMENT', will have a key named 'ORAC_INSTRUMENT'. The original keys will not be in the returned hash. If left blank, no prefix will be added.

This method returns a hash of generic headers. This function dies if the header translation fails in any way.

translate_to_FITS

Converts a hash containing generic headers into one containing instrument-specific FITS headers.

  %FITS_headers = translate_to_FITS(\%generic_headers,
                                    class => \@classes,
                                   );

This method takes a reference to a hash containing untranslated headers, and a hash reference containing the following optional keys:

• class - A reference to a list of subclasses to try to use for header translations. This list overrides the default list. If left blank, the default list will be used.

• prefix - A string prefix to remove from the generic header key before doing header translation. Why you would want to do this is if you've used a prefix in the translate_from_FITS call, and want to translate back from the generic headers returned from that method. If left blank, no prefix will be removed.

This method returns a hash of instrument-specific headers. This function dies if the header translation fails in any way.