SOLARNET Metadata Templates

The SOLARNET Schema provides several useful methods for working with metadata attributes.

  • Keyword Templates: astropy.io.fits.Header objects can be created as templates based on input options, where the header contains all default and required attributes with empty values.

    • This enables users to easily fill in the necessary metadata for their data products in an partially populated FITS header format.

  • Keyword Detail Information: You can also retrieve detailed information about specific attributes or all attributes in the schema.

    • This is useful for understanding the requirements and context of each metadata attribute.

    • An astropy.table.Table is returned, which can be easily viewed or exported to various formats (e.g., CSV, HTML).

Creating Attribute Templates

Attributes templates are created using the attribute_template() method of the SOLARNETSchema class. This method allows you to generate a template astropy.io.fits.Header object populated with all required keywords, and values set to None.

This can serve as a useful tool for prototyping FITS header metadata that is compliant with the SOLARNET metadata standards. Users can fill in the appropriate values for required attributes, and add optional attributes as needed to their headers.

Options available for generating templates include:

  • primary (bool): If True, the template will include keywords required for primary HDUs.

  • obs (bool): If True, the template will include keywords required for observation HDUs.

  • observatory_type (str): You can specify the type of observatory to include observatory-specific required keywords.

    • This must be one of ["ground-based", "earth-orbiting", "deep-space"]

  • instrument_type (str): You can specify the type of instrument to include instrument-specific required keywords.

    • This must be one of ["Imager", "Spectrograph"]

from astropy.io import fits
from solarnet_metadata.schema import SOLARNETSchema

# Create a schema object
schema = SOLARNETSchema(use_defaults=True)

# Get a template for ground-based imager
template: fits.Header = schema.attribute_template(
    primary=True,
    obs=True,
    observatory_type="ground-based",
    instrument_type="Imager"
)

This returns a astropy.io.fits.Header object where keys are required attribute names and values are None. You can then fill in the appropriate values for your data.

Getting Attribute Information

You can retrieve detailed information about specific attributes or all attributes using the attribute_info() method of the SOLARNETSchema class.

This method returns an astropy.table.Table containing the attribute information.

Details provided include:

  • Attribute name

  • data_type (str): The expected data type of the attribute value.

  • default (Any | None): The default value for the attribute, if any.

  • description (str): A description of the attribute and its context.

  • human_readable (str): Provides a default value for the keyword comment.

  • required (str): Indicates if the attribute is required

  • origin (str): Indicates the origin of the keyword attribute. For more information, see 19 Alphabetical listing of all keywords with section references

  • pattern (str | None): For attributes with variable indices (e.g., NAXISn, CTYPEia), the pattern used to generate the attribute names.

  • valid_values (list | None): A list of valid values for the attribute, if applicable.

You can optionally specify an attribute name with the attribute_name parameter to get information about a specific attribute.

For more information on the values provided, see the table in the Attribute Schema Format section.

from astropy.table import Table
from solarnet_metadata.schema import SOLARNETSchema

# Create a schema object
schema = SOLARNETSchema(use_defaults=True)

# Get information about a specific attribute
author_info: Table = schema.attribute_info(attribute_name="AUTHOR")

# Get information about all attributes
all_info: Table = schema.attribute_info()

This returns an astropy.table.Table containing all the schema information for the requested attribute(s).

Accessing Default Attributes

Default attributes can be specified in the schema for attributes that have a common default value. These default values are loaded in the schema upon instantiation and are available through the default_attributes property of the SOLARNETSchema class.

The default_attributes property returns a astropy.fits.Header object containing all attributes that have a specified default value in the schema, with their values set to the defined default.

The default attributes are included in the attribute templates generated by the attribute_template() method, with their values set to the specified default.

from astropy.io import fits
from solarnet_metadata.schema import SOLARNETSchema

# Create a schema object
schema = SOLARNETSchema(use_defaults=True)

# Get the default attributes
defaults: fits.Header = schema.default_attributes

This can be useful for quickly populating a FITS header with common default values for required attributes in your data files. The returned astropy.fits.Header object can be easily manipulated or converted to other formats as needed.