ESS 265

Chapter 11.

Operation of a Distributed Information System: The Planetary Plasma Interactions Node Example

Raymond J. Walker

March 17, 1999

• Why bother?
• What are the Planetary Data System (PDS) and the Planetary Plasma Interactions Node (PPI)?
• How is data prepared?
-PDS documentation
-Peer review
• How do you locate and access data?
-DITDOS
-CDROM
-WWW

• What about Space Physics?

• Why bother with data management and archiving?
-Many of the data are irreplaceable.
-Having many scientists work with the data leads to innovation and maximizes science return.
-It is the law.


• Why bother with a distributed system?
-The best data products reside with people who use them to do their science.
-No university or laboratory has the expertise necessary to understand all of the data from all of the instruments involved in planetary science.

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• PDS is a distributed data system managed by the Jet Propulsion Laboratory (JPL)
PDS has 5 science nodes

-Atmospheres Node - New Mexico State
-Geosciences Node - Washington University
-Planetary Plasma Interactions Node - UCLA
-Small Bodies Node - University of Maryland
-Rings Node - NASA Ames Research Center
• PDS has 2 support nodes
-Navigation and Ancillary Information Facility - JPL
-Imaging - JPL and USGS Flagstaff

• We have studied the interaction of the Earth's magnetosphere with the solar wind for over 40 years.
• Mercury, Jupiter, Saturn, Uranus and Neptune have a similar interaction- supersonic solar wind interacts with a magnetic field to form a magnetospheric cavity.
• At Venus and Titan (when outside Saturn's magnetosphere) interact with the flow to form an induced magnetospheric cavity.
• The Moon has a remanent magnetic field.
• Mars too has localized field concentrations.
• The small size and large amount of gas that evaporates from a comet make its interaction with the solar wind unique.
• Asteroids may have a strong interaction with the solar wind.
• Ganymede has an intrinsic magnetic field and small magnetosphere within the vast jovian magnetosphere.
• Io is embedded in a sub-Alfvenic flow and the plasma impinging on Io is of Ionian origin.
• Europa and Callisto have induced magnetospheres possibly related to a subsurface ocean.
• Other planetary moons interact with plasma displaying a broad range of interaction parameters.
• A new scientific discipline concerned with the physics of magnetospheres and ionospheres.
-Interaction between the solar wind and planetary obstacles.
-Processes which occur within the induced or intrinsic magnetospheres.
-Studies of the flow of energy and mass through these systems.
-Interaction of planetary wind with satellites.
• Planets are closely coupled systems.
  
  -Planetary atmospheres evolve due to plasma processes.
  -Surfaces are bombarded by energetic particles and flowing plasma.
  -Interiors of planets can be probed with low frequency magnetic variations.

• Number and variety of planetary plasma data sets is large.
• Data for a given study often come from several instruments on a spacecraft in addition to Earth based observations.
• Distributed node
-University of Iowa (W. Kurth - outer planets)
-UCLA (C. T. Russell -inner planets)
-Stanford ( R. Simpson - radio science).

• In situ observations
-Magnetometers and electric field instruments provide low frequency magnetic and electric field observations.
-Energetic charged particle instruments provide ion and electron fluxes and composition from few keV to GeV.
-Plasma detectors provide information about the plasma distribution function and composition for cold and thermal energy particles.
-Plasma wave detectors and AC magnetometers provide information about plasma waves.
• Remote sensing
-Radio astronomy -Ultraviolet images of planetary magnetospheres. -Images in UV and visible for aurora. -Radio signals to probe planetary ionospheres.

• Meet with the principal investigators at an early stage of the mission.
-Introduce PDS.
-Begin planning the archive.
• Acquire electronic copies of references describing the instruments and their operation.
-Scan if necessary.
-Obtain permission from the copyright holder.
• Acquire data and documentation from PI or designated data provider.
• Prepare peer review package
• Prepare documentation to PDS standards (PDS catalog templates and PDS labels).
Package data, documentation and any PI provided software onto CDROMs (CDR).
• Peer review
-Distribute CDROMs to scientists who are willing to check the data and its usefulness. -Make the CDROMs available through the PPI Node on-line system. -Resolve any discrepancies in the data or documentation.
• Produce final CDROMs
• Load PDS Catalog
• Distribute data to the scientific community.

• PDS Catalog Templates- Metadata to assist scientists in locating PDS data
-Instrument
-Data set
-Instrument host
-Mission
-Personnel
-References
• PDS Labels - Metadata describing the data.
Format
Instrument
Instrument paper
Mission paper
Data set

• PDS Catalog Templates- Metadata to assist scientists in locating PDS data
-Instrument
-Data set
-Instrument host
-Mission
-Personnel
-References
• PDS Labels - Metadata describing the data.
Format
Instrument
Instrument paper
Mission paper
Data set

Peer Review Process

• Panel of scientists reviews the data and documentation.
-Documentation is reviewed for completeness and correctness.
-Data are reviewed for correctness.
-Data file descriptions are reviewed for adherence to standards.
• Data are made available to the scientific community as soon as electronic versions are received by PPI.
-Data are listed as "under review" until they have completed the review process.
-Users are encouraged to report errors or deficiencies in the data or documentation back to the PPI Node as part of the review process.

PPI Node-Data Management Considerations

• The archive bytes of data.
-12 bytes of data
-552 data sets from 85 instruments on 15 spacecraft.
• Scaleable data management- same tools Node uses to manage the entire collection
can be used by an individual scientist to access data on a single CDROM.
• Must adhere to PDS standards.
• Minimize amount of effort to generate a "product".
• Every product is completely self-contained.
  -All necessary documentation and inventory information required to use the science data. -Larger systems are built by using products as building blocks.

• On-line information system for the PPI Node is an inventory and access system for every product offered by the PPI Node.

PPI Node- Inventory Tracking

• Requirements
-Track the data regardless of its physical location.
-Track the data through modifications or revisions.
-Indicate associations between various data.
-Allow users to select pieces of databases and reassemble them into new databases.
• Solution
-Distributed Inventory Tracking and Data Ordering Specifications (DITDOS).
-Tools to assist in the assembly of metadata and data in a networked environment.
-Servers for delivering metadata and data.
-Clients to access the server.
-Report generation tools.

-Stand-alone applications for individual users.

DITDOS

1. Three types of inventories.
-"Database" describes collections of products (Galileo data at Jupiter, Voyager 2 data at Neptune).
-"Product" is a collection of datasets which are contained on a single deliverable medium (CD-ROM).
-"Datasets" describes collections of physical data holdings.

• Defined by investigators
• May be more than one dataset from a given instrument.
-Each physical data holding is a "member".

2.Inventory description language.
-Portable means of describing inventories.
-No restriction on the supported formats.

Database Table

Product Table

Dataset Table

Member Table

Curator Table

Privileges Table

• A language for constructing inventory entries.
• Command/directive/options syntax.
• Example-

define dataset refname = VG2-U_LECP-3-DDR-T860125_AVERAGE-15M-1_0\
sysname=/LECP/AVERAGE/15M/DATA/t860125\
status=online curator=ditdos class = "UCLA/IGPP Flatfile"\
instance="Version 1.0"\
desc="Voyager 2 LECP 15M average data near Uranus"

3. Client/server protocol
-Tagged packets
-Small set of tags and request/response requirements.
-Structured Query Language queries.
4. Interface between client or server and agents.

-"Agent" is an application which performs specific operations on data.
-Clients and servers look like files to the agent so preexisting applications can be used as agents.
5. Syntax used to specify which agents are used to perform specific operations on data in a specific format.

Class = UCLA/IGPP Flatfile
instance = Version 1.0

reader.native = ffconvert
writer.native = ffwrite
writer.ascii = ffwrite-ascii
viewer.text = xffviewer
viewer.graphic = xffgraph

• Generating DITDOS inventories
-Organize product by following PDS standards for volume design.
-Inventory building tool scans the volume and uses the PDS labels, the data and the location of the data on the volume to populate the inventories.
• All data holdings of the PPI Node are accessible through the WWW.
-Data can be displayed on the screen, delivered to the user's home computer or ordered on CD-ROM.
-DITDOS agents update the system automatically.
-URLs http://www.igpp.ucla.edu/ssc/pdsppi/Welcome.html or http://pds.jpl.nasa.gov/pds_home.html
• Stand-alone platform independent tools are available to explore an inventory and extract data.

• Space physics currently does not have discipline wide data effort.
• Few data are available in an archival form.
• Documentation is often incomplete.
• The best efforts in space physics have come from individual scientists in the space physics community - Many of those efforts have been organized in a Web page at http:spds.nasa.gov/spds.html

• The National Space Science Data Center provides archival storage for NASA space physics and planetary data.
• NSSDC provides online data directories.
• NSSDC provides online data to select missions.
• NSSDC doesn't set or enforce data standards but they do have a standards development office.
• NSSDC can be reached at http://nssdc.gsfc.nasa.gov

• Online data services tailored for ISTP scientists.
• Online services include directory searches, online plots of survey data, online plots of trajectory data.
• Data are available on CDROM.
• Data are in the Common Data Format (CDF).
• The ISTP data resources are available at http://www-istp.gsfc.nasa.gov/istp/

• Sun Earth Connections data effort will be part of the Space Science Data System which already includes the planetary and astrophysics communities.
• Distributed system with three science nodes and a management node.
-Solar physics
-Remote sensing
-In situ observations
• Data will be prepared by data nodes distributed throughout the SEC community.