JWST Data Discovery

The MAST Discovery Portal is the primary web interface for discovering, visualizing, assessing, and retrieving calibrated data products from the JWST science calibration pipeline. The portal also serves the associated calibration, guide star, and engineering data products.

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Accessing JWST data

Words in bold are GUI menus/
panels or data software packages; 
bold italics are buttons in GUI
tools or package parameters.

There are a variety of ways for researchers to access JWST data of interest, including the MAST Discovery Portal (hereafter, Portal) which is the primary web interface for discovering, visualizing, assessing, and retrieving archived data. The portal also provides access to ancillary and engineering data related to the observations. Users may evaluate contemporaneous calibration reference data that were used to remove the instrumental signature from the science data products. They may also discover data through a programmatic (software-based) interface such as the MAST Applications Programming Interface (API), and through various community tools. The Portal also provides a subscription service that allow users to be notified as data from new JWST observations become available through MAST.

Data product types

The JWST Data Management System (DMS) produces many products for each JWST observation, including the science files produced by the science calibration pipeline. The exact type and number of products depends upon the instrument, its configuration, and operating mode. Consult the Data Product Types article for a detailed description of the internal organization and content of each science product, and the Data Product File Formats article for all product types.

Minimum recommended data products

Of the many different data products produced by the processing pipeline, a subset has been identified as essential for extracting the intended science from the data, or for users who wish to recalibrate lower-level products with the calibration pipeline on their own platforms. See the Minimum Recommended Products (MRP) article in the MAST Portal Guide for details. 

MRP Checkbox

MRP products are selected by default in the MAST Portal. The MRP checkbox in the Download Manager must be de-selected in order to view and retrieve raw- and intermediate-level data products, and all ancillary products including guide star data.

MAST Discovery Portal

MAST implements various protocols of the Virtual Observatory (VO) including those for image, table, and spectral data access. As part of these protocols, MAST core services operate using the Common Archive Observation Model (CAOM).  As a result, MAST data can be searched and retrieved by VO-aware applications. 

Archived data

The MAST Portal offers great flexibility in customizing queries to identify datasets from several hosted NASA missions to explore and retrieve. See the JWST Data Exploration article for a detailed example of a search for JWST science data using the Portal. The following tutorials may be helpful for new Portal users:

Engineering data

Data associated with the thousands of engineering telemetry points on JWST are stored in the MAST Engineering Database. Engineering data are obtained contemporaneously but are not packaged with the science data. See the Engineering Data article in the JWST Archive Manual for context. The data take the form of time series, and they may be searched with the Archive User Interface (AUI) by means of an identifier, or mnemonic. See the Using the Engineering Data Portal article in the JWST Archive Manual for details. Users may access the engineering database via a direct link to the query interface or, after querying the Portal for science data, through a link on each row of a search results table.

Anticipated data

At any given time some observations in a program may have been executed, archived, and become available to the community. Some archived observations may temporarily be restricted to those with exclusive access while still other observations may remain to be obtained. Investigating teams and the broader community each have an interest in data availability. In order to encourage the greatest possible use of JWST data in MAST, a subscription service will notify registered and subscribed users when one of the following observation-related events occur:

  • new observations are archived,
  • archived data have been reprocessed, or
  • restricted-access data become available to the public.

Users may tune the notifications by mission, program ID, event type, and science product. Users may establish or cancel their subscription through the MAST Discovery Portal, change the media and frequency of notifications, and change the selection criteria for notifications. See the following tutorial:

Planned observations

MAST provides the capability to compare the position of one or more user targets against extant and planned observations to identify potentially duplicate observations. Duplicated observations are, in general, not allowed so it is in the proposer's best interest to perform this check prior to submitting a proposal for review. Read the article Identifying Potential JWST Duplicate Observations to see how to query planned observations.

The orientation of planned observations will not be known precisely until they are scheduled. Therefore, the position given in MAST of any planned parallel observations will not be accurate, and could be different from the listed coordinates by up to several arcminutes.

Virtual observatory tools

Many community software applications are capable of accessing remote data using protocols developed for the Virtual Observatory. You may have used them before without being fully aware of how such data were obtained. Table 1 provides an incomplete list of community, VO-aware applications for visualizing and exploring archived astronomical images, spectra, and catalogs:

Table 1. An incomplete list of community, VO-aware applications for visualizing and exploring archived astronomical data

ApplicationPrimary StrengthDescription
AladinAnalysisInteractive sky atlas, capable of overlaying archived images and source catalogs
DataScopeDiscoveryPosition-based search engine for astronomical archives
SAOimage/DS9AnalysisImage display tool, capable of overlaying archived source catalogs
SIMBADRetrievalAstronomical catalog search engine
SkyViewDiscoveryAstronomical image search engine
TOPCATAnalysisCatalog cross-match, filtering, sub-setting, and visualization tool
VizieRRetrievalAstronomical catalog search engine



Pence, W. D., et al. 2010, A&A, 524, A42
Definition of the Flexible Image Transport System (FITS), version 3.0

MAST Discovery Portal

MAST Portal Guide

JWST Archive Manual

MAST Engineering Data Portal

Latest updates

  • Added information about guide star data, and simplified the description of the engineering database.

    Additional information on identifying duplicate observations, including a link to the "how-to" page. Rewrote subsection on the engineering database interface, with a link to Data Exploration article
Originally published