The following is copied from OAIS v1 (2002) and may be out of date

1 Planetary Data System Archive

1.1 DOMAIN

Domain and Consumers.The Planetary Data System (PDS) is chartered to provide data archiving services, data access and expert help to the NASA-funded planetary science community. The PDS is a distributed system with a Central node at the Jet Propulsion Laboratory and discipline nodes (imaging, geosciences, atmospheres, planetary plasma interactions, small bodies, rings) located at universities around the country. The early focus has been on restoring historical mission data and has produced several hundred CD-ROM volumes containing about 80 per cent of the important planetary data archives. There has been an increased emphasis on providing access to the general public for educational outreach over the past several years.

Data Producers. Planetary data sets originate with NASA flight project data management and science teams (new data, some restorations), individual scientists (newly processed or value-added data) or via the PDS discipline nodes (restorations and value-added data). At least 50 percent of the PDS resources have been devoted to restorations over the past seven years, with several more years of work needed to capture all historical data.

1.2 INGEST PROCESS AND INGEST INTERFACE

The PDS has developed a very formal interface with the major data producers (flight projects). This interface is documented in the Data Preparation Workbook and involves substantial interaction between node personnel, data engineers and project representatives. A Project Data Management Plan, signed by the PDS project manager provides the basic project data description and agreement to deliver to PDS. Since about 1993 all NASA announcements for Planetary investigations or analysis require that all data generated be delivered to PDS in conformance with PDS standards.

Submission Agreements

Projects provide a Project Data Management Plan (PDMP). Sometimes a more specific document, the Archive and Transfer Plan, supplements the PDMP, providing extended product documentation and a schedule of deliveries.

Individual scientists can propose to be ‘data nodes’ and receive funds from a PDS discipline node for preparing restored or value-added data sets for inclusion in the archive. There is no formal submission agreement for data nodes.

The PDS discipline nodes each maintain a list of outstanding restorations. These are worked-off based on their priority within discipline. At some point this list will be completed and only new project or data node data sets will be ingested into PDS. There is no formal agreement associated with discipline data restorations.

Each data set that is identified for ingest in PDS is assigned to a Central node data engineer. It is the responsibility of the data engineer to see that all archiving steps are completed. The archiving steps are called out in the PDS Data Preparation Workbook.

Typical Data Delivery Session. Typically a delivery session will consist of a single data set contained on one or more volumes of CD-ROM or CD-Recordable media. A data set is defined within PDS to be a group of homogenous data granules at the same data level (raw, decalibrated, reduced) which differ only in time of acquisition and major category of target body. For example, the images of Jupiter taken by both Voyager spacecraft comprise a single data set. The standard process includes up-front negotiations between PDS and the provider; the production of test products which are evaluated in the peer review; revised final test products which are validated by the data engineering staff at the central node; approval and production of CD-ROM volumes; distribution by the appropriated discipline node or the central node; entry of the data set into the PDS central catalog; and entry of the data set into the NSSDC ordering system.

Transformation Process. In most cases the original data formats are maintained when data is brought into PDS. This allows existing software tools to continue to be used with the data. Much of the data preparation involves carefully documenting the data format and preparing metadata (granule labels, index files and catalog templates).

Validation. Validation is generally performed as part of the peer review of a product or by using validation tools. In some cases (for example, Magellan), the project develops its own internal validation process. The main validation tool of the PDS is the Volume Verifier. This program is run by the Central Node data engineers on each product delivered from a project or a data restoration. It validates the format and content of all product labels, and validates data files using checksums.

Security. The only area where any special security issues exist involves the receipt of proprietary data. Some projects have one-year proprietary periods before data in released to the science community. The PDS policy is to avoid receipt of any proprietary data sets during the proprietary period.

1.3 INTERNAL FORMS

The PDS has developed standards for documenting data sets (templates) and individual data products (PDS labels) using a keyword=value label system called the Object Description Language (ODL). Recommendations are also provided for volume organization and data product formatting to optimize the utility of resulting data products.

The PDS standards are specified in the PDS Standards Document. Standard documentation requirements include templates describing the data set, instrument, mission, etc. These templates are included on data volumes and also entered in the PDS high-level catalog. Standard terminology is maintained in the Planetary Science Data Dictionary (PSDD), which is jointly maintained by the PDS and the multi-mission ground data system. The metadata values for new data products are carefully compared with the PSDD and existing values used wherever possible. Additions are made to the PSDD to add new standard values to accommodate new data sets and when justified new keywords are added to the PSDD. Data products can have specialized metadata values which are not cataloged in the PSDD.

The PDS product labeling system is flexible enough to allow nearly any data structure to be described. Labels can be attached to the beginning of the data file or detached in a stand-alone text file which points to the data file. In some cases a single label file is used to describe multiple data files. Detached labels can be used to describe data stored in other formats (FITS or HDF, for example). In cases where complicated raw telemetry formats are stored the Software Interface Specification (SIS) for the product is included in lieu of descriptive labels.

Archive Volume Components

An archive quality data set is required to contain the following components:

– AAREADME.TXT - Text summary of data contents;

– VOLDESC.SFD - Standard volume label;

– VOLINFO.TXT - Text description of data contents;

– CATALOG - DATASET.CAT, MISSION.CAT, INST.CAT;

– INDEX - ASCII index for each granule on the volume;

– SOFTWARE - Software needed to interpret/display the data;

– CALIB - Calibration data sets;

– BROWSE - Browse products for this volume.

Peer Review. All restoration and data node-produced data sets are required to undergo a peer review before acceptance as archive products. Products produced by flight projects do not go through a formal peer review process. In general, there is ongoing negotiation between the data engineer or the discipline node staff and the data producer. The peer review team consists of a number of scientists familiar with the data set, the discipline node leader and one or more data engineers. All product documentation and sample products and software are supplied to the peer review group for evaluation. The peer review group determines the adequacy of documentation and quality of the data products and either approves the product or provides a set of liens which must be fixed prior to approval. The PDS nodes and data engineers have access to a Volume Verifier tool which aids in validating the quality of an archive volume. The volume verifier checks internal checksums, verifies that the index contains entries for all data products and validates the volume templates as well as the descriptive keywords supplied for each product.

Delivery Media. Discipline restorations and data node products are recorded on CD-ROM or CD-recordable media as a standard practice. Flight projects are urged to provide archive quality products on CD media but may not be able to due to funding constraints. Products delivered to PDS on magnetic tape media are assigned to the PDS restoration queue. It is the goal of PDS to convert all data sets to CD-ROM or CD-recordable media which is replicated at a separate geographic facility. This separate facility is generally the National Space Science Data Center (NSSDC) at Goddard Space Flight Center.

1.4 ACCESS

Nearly all access to PDS data sets is via the CD-ROM volumes which are distributed to the entire research community. Large discipline node data collections including a substantial volume of CD-ROM data are accessible via the Internet. Several of the discipline nodes have developed on-line retrieval systems customized to meet the needs of their discipline scientists.

Finding Aids. The Pilot PDS devoted substantial resources to designing a central catalog system and distributed query and processing capabilities at the discipline nodes. These efforts were largely dropped as the Planetary Data System focused on data restoration rather than data access. In general, most of the user community already had home grown tools for data analysis and were most concerned with getting access to the data sets. The growth of the user community due to Internet and increased usage of CD-ROM readers has spurred to prototype a more consistent finding aid. The PDS Navigator has been developed for selecting images from the Clementine mission. It includes three components, a forms-based traditional database retrieval capability, an image-based retrieval and a text-based retrieval.

Security. The high-level PDS catalog can be accessed via a group account. Most of the data access services at the discipline nodes require the user to obtain a valid account on the node computer. All PDS data sets are certified "General Technical Data Available" by the Department of Commerce and are distributable worldwide.

Customer Service/Support. The order function of the PDS is distributed. Data inventories are kept at NSSDC, the PDS central node and at each discipline node. In general each site serves a special group of users:

– discipline node - members of the NASA funded discipline;

– central node - other NASA scientists and engineers, other agencies;

– NSSDC - other scientists, agencies, public and foreign users.

The PDS Operator at the central node handles requests for PDS documentation or standard data products. The discipline nodes handle data requests from within their discipline and also provide expert help in the utilization and interpretation of the data. Access to tools is also provided.

The vast majority of data dissemination is done via CD-ROM disc. Several hundred copies of over 500 titles have been distributed to date.

Event Based Orders. Nearly all PDS distribution is done via event based orders (i.e., subscriptions or standing distribution lists). It is the responsibility of each discipline node to maintain a distribution list for its discipline scientists. This list determines the order amounts for most CD-ROM titles. The central node maintains a distribution list for engineering and management personnel and for other external recipients (reciprocal distribution, software developers).

Media/Network Use. Nearly all final products are delivered to the user community on CD- ROM. Archival products that need not be widely distributed are stored on CD-Recordable media, with a duplicate copy provided to the NSSDC. Most PDS data is available for downloading via anonymous ftp connection to a large CD-ROM jukeboxes at the central node and the imaging node.

Data Manipulation. Each discipline has a suite of government developed analysis tools which can be applied to the discipline data sets. These software packages are available for UNIX workstations or VAX VMS platforms. Several nodes provide the user a menu of processing functions that can be performed on selected data and will carry out requested processing and provide the results electronically or via media. The most widely used commercial tool is IDL.

Pricing Policy. The PDS distributes data to legitimate NASA researchers for no charge. There are no charges for on-line computer usage or data processing to NASA researchers. The NSSDC distributes CD-ROMs for $10 per volume.

1.5 SPECIAL CHARACTERISTICS

PDS has invested a substantial engineering effort in its common data dictionary, data standards and procedures for preparing archival quality data sets. By having these standards in place the PDS is able to demand better quality data sets of its data providers.