PDS4 Bundle for the GRAIL Gravity Model dataset

This bundle contains GRAIL gravity model data products and associated
documentation migrated from the PDS3 volume. It contains gravity models in map,
ASCII, and binary formats.

The bundle contains the following collections:

- Three data collections:
     rsdmap - maps of gravity field
     shadr - spherical harmonics stored as ASCII text
     shbdr - spherical harmonics stored as binary files
- Two document collections
     catalog - PDS3 catalog files
     document - various GRAIL and radio science documents

Note that because of PDS4 requirements on document formats, the original GRAIL
documents files were converted to PDF/A formats where possible. A few cases are
store as ASCII text files. In addition, four documents were copied from the PDS4
radio science documentation bundle. The original document directory will be
saved offline and users can request a copy of the documents in original format.

Each product in this bundle is described by a PDS4 label in a separate file with
the same name as the product file described but with the extension XML. PDS4
labels are XML (eXtended Markup Language) files that conform to the PDS4
Information Model XML schema at https://pds.nasa.gov/pds4/schema/released/. The
PDS4 labels are best viewed in an XML-aware text editor, and may be used by
software that can manipulate XML documents.

Note that the PDS4 labels and other PDS4 products are merged with the PDS3
volume such that all the PDS3 files and directories are preserved, except for
the document directory as noted above. Thus, users who want access to the PDS3
labels can continue to use them. All data products have been given PDS4 labels.
Some PDS3 files remain but are not considered part of the PDS4 bundle, e.g., 
aareadme.txt and voldesc.cat files in the root directory of this bundle
and the extras directory. The aareadme.txt file describes the structure of the
original PDS3 dataset. The voldesc.cat is a PDS3 catalog file for the volume.

This bundle was created and archived by the Geosciences Node of the Planetary
Data System. Questions about this bundle may be directed to
geosci@wunder.wustl.edu.