NASA’s Planetary Data System (PDS)

Michael F. A’Hearn

24 Jul 2007 mfa - 2

PDS Overview

• PDS - the organization– An organization that archives and distributes all of

NASA’s planetary mission data (and much other planetary data) according to PDS standards

• PDS - the archiving standard– A standard that defines how to label data products in

order to make them automatically readable and interpretable and how to document everything for future generations

• PDS - the archive– A distributed but centrally searchable archive of all

data from NASA’s planetary missions

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PDS Goals

• Ensure that all data from NASA’s planetary missions are archived in a manner that will make them usable far into the future

• Acquire and archive other planetary data relevant to NASA’s missions

• Distribute the data to researchers• Provide appropriate tools for finding the right

data• Work with non-US partners to ensure

compatible archiving of all planetary missions

• A wealth of data - waiting to be analyzed!

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PDS Organization

• PDS is a distributed system, with Discipline Nodes headed by various scientific specialists– DN leads selected competitively based on

management and on scientific approach to data– PDS started as part of the R&A program run by

active researchers• PDS has centralized capabilities for searching

data at all the nodes and also a central repository for PDS-wide documents, standards, policies, etc.– At the Engineering Node at JPL

• Individual scientific discipline nodes provide capabilities that are special to their area as well as archiving all the data relevant to that discipline

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PDS Organization

Program Executive: Bill Knopf at NASA HQ Program Manager: Ed Grayzeck at NASA GSFC

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PDS Organization - Staff

• Key planetary scientists you may recognize– Atmospheres - Reta Beebe, Nancy Chanover– Geosciences - Ray Arvidsen, Ed Guinness– Imaging - Lisa Gaddis– Planetary Plasma Interactions - Ray Walker, Steve Joy– Rings - Mark Showalter, Mitch Gordon– Small Bodies - Mike A’Hearn, Ludmilla Kolokolova, Don

Davis, Mark Sykes, Dave Tholen• The scientists ensure the scientific value and

usability of the data• Many other staff are better known for their

PDS activities rather than for scientific work• With many different scientific PIs, PDS

functions as much like a federation as like a coherent entity

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PDS - An Archiving Standard

• Standards go back to Proto-PDS in late 1980s, prior to the current structure of discipline nodes

• Standards allow many different types of data

• Standard evolves to accommodate new needs

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PDS Standards - Data Model

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PDS Standards - Data Products

• Product = image or spectrum or time series, etc. including label and, e.g., supplementary data

• Labels are like FITS headers– Keyword = value format

• Important differences from FITS– Label can be attached to data product or a separate file

(FITS headers must be attached)– Keywords are ALL defined (FITS defines only a few and

allows almost unlimited user-defined keywords)– Format of data is not prescribed (FITS requires, e.g., 2880-

byte records) but the format must be described in the label– There are significant differences among discipline nodes,

e.g., in how data are formatted

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PDS Standards - DI Image

• FITS version has FITS extensions for quality factors and SNR

• Generally in PDS, the PDS label is more reliable than the FITS header for documenting the data product– But it is often less

extensive - many engineering keywords are omitted

• Product ID = MV0173728448_9001040_001_R_FIT– Used to find the image

in indices or other toolsJPEG version of image described in previous label

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PDS Standards - Sample Label

And continuing with more …..

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Label continued

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PDS Standards - Cassini Image

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PDS Standards - Different Image

A Cassini image of Titan - very different structure

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PDS Standards - Data Organization

• PDS requires a lot of ancillary information– Both raw and calibrated (physical units) data are required from

NASA missions– Geometry is required either in the labels or in separate files or in

SPICE– Catalog files are used to load the central search facility– Documents (including ascii versions) are required to explain

enough that any intelligent scientist 20 years from now should be able to recalibrate and use the data (with the help of library references)

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PDS - The Archive

• All NASA planetary missions are required to archive in PDS (since mid 1990s)– Require raw data, calibrated data, & derived products

(maps, etc.) as appropriate– Generally basic raw & calibrated data due in 6 months

• Archive also includes data from ESA and IKI and ISAS missions to comets Halley & Grigg-Skjellerup & some more recent shared archives

• Archive also includes selected planetary data from astrophysics missions (IUE, HST, etc.)

• Archive includes selected ground-based datasets, particularly at SBN and at Geosciences

• Archive includes comparative databases for small bodies

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PDS - Using The Archive

Get a viewer for PDS dataTry NASAView

Get some data

http://pds.nasa.gov/

Nodes

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PDS - Searching the Archive

• Central search facility searches by mission, target, instrument, or instrument type

• Start at http://pds.nasa.gov/

• Click on search to go to http://starbrite.jpl.nasa.gov/pds/index.jsp– Shown at right

33 interplanetary missionsplus earth-orbital & ground-based data

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Searching at DNs

http://pds-smallbodies.astro.umd.edu/

Start at the central, PDS-wide search if you aren’t sure which data you want or where the data are availableStart at a DN or even at a subnode of a DN if you know which data you want and which DN has it

http://pds-geosciences.wustl.edu/

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PDS - Sample Ground-based Data

• You can even find your own data in PDS

• This is one of many ground-based surveys and special datasets

• And you see whom to ask locally about the PDS!

http://www.psi.edu/pds/resource/s3os2.html

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PDS - Searching at PPI

• Find the magnetic field measurements (tables) at Gaspra & Ida at PPI

• In this case, the data are off-line and will be mailed to you

• In this case, they also have some errors noted after the CDs were produced

http://www.igpp.ucla.edu/cgi-bin/ditdos?filter=GOMA_3001,GOMW_0001,GOPR_2001&title=Gaspra_DataGetting here from the top level is easy

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Tools You Should Have

• Simple Viewers (all free, available on-line)– NASAView - intended for all PDS products but has some limitations (I

broke it yesterday on a product from Geosciences)– ds9 and fv - useful only for PDS-labeled FITS files

• A good analysis environment– IDL (somewhat expensive)

• A versatile environment for “exploring” your data as well as analyzing it• Library of astronomical routines at NASA-GSFC• Needs an I/O routine such as SBN’s readpds.pro (which works on many

but not all products)– ISIS (free)

• Widely used by planetary geologists with many built-in functions• Supported via Imaging Node of PDS at USGS• I/O works only with products designed for ISIS compliance (not FITS)

– IRAF (free)• Can be used only for PDS-labelled FITS files since there are not (yet) any

I/O routines for PDS-labeled products• SPICE (free)

– Tool for working out geometry of measurements (if not already in keywords or for updating the values)

– Supported via NAIF on many platforms & languages

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Problems?

• Go back and read the “help” pages, e.g. at SBN– Guidelines to help

reviewers access the data as well as review them

• Includes a list of tools– Guideline for all the

mysterious file types that you will encounter

• Contact PDS– Usually the node closest

to the data with which you have a problem

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PDS - Help functions

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PDS - Software Tools

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PDS - Archive File Types

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PDS - Archive File Types (cont.)

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PDS - Archiving Future

The volume of data is growing faster than the number of scientists working with the data!