Data Exploration

Investigators have a variety of tools at their disposal with which to explore JWST data, and data from other missions and surveys, both within and outside of the context of the MAST Discovery Portal. Web- or desktop-based tools enable Archive users to plan JWST observing programs, and to place JWST observations in the context of archived astronomical data.

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Tools for data exploration

Once a search for data has been performed, there are a number of tools available to help sort, visualize, and refine the results. Many of these are built into the MAST Discovery Portal (hereafter, Portal), but there are also many additional tools available from the community at large. These tools enable users to explore JWST data, and data from other missions and surveys, view areas of digital sky surveys, select images and footprints from popular missions and surveys, cross-match and plot source catalogs, and view time series of selected targets. These capabilities facilitate planning JWST observing programs, exploring JWST data once the observations are available in the Archive, and understand planned or existing JWST data in the context of the world-wide collection of data on a given source or field. Below are descriptions or links to tutorials on how to use these tools.

Native MAST tools

Target/Position query

A simple query of a target name or position in the Portal will often bring up an abundance of information, with many ways to sort and filter in order to get exactly the data you are looking for.

Figure 1. Result of a Data Discovery Portal query around M51, filtered for GALEX and WFC3/IR images, with selected observations highlighted

The top of each search results tab provides a number of tools for the user, including buttons for adding selected files to the download basket and exporting the search results table, as discussed in the Data Retrieval section.  From here you can cross-match the current search results with another catalog from either MAST or CDS, and to create custom plots from various parameters within the current search results. There are three panels below to filter, select, and visualize the search results.

Left panel: filter the search

The leftmost panel of the results page provides a number of filters to isolate specific data characteristics of interest. These include product types (image, spectrum, timeseries, etc.), mission (HST, SWIFT, FUSE, etc.), instrument, filters, waveband (optical, UV, infrared, etc.), observation start time and duration, and several others.  These filters can select a wide range of specific requests and combinations of constraints for narrowing down a large set of search results.

Middle panel: select results

The List View in the middle of the results page table with detailed information for all current search results after the application of user-select filters.  Each column in the table may be used to sort the results as the user wishes, and the columns themselves may be selected to suit the user's needs (Edit Columns button in the upper-left corner of the panel). Image previews may also be added to the table with the Show Preview checkbox. For larger views of these preview images, switch from the List View tab to the Album View tab, where the same search results are laid out in a tiled array.  User sorting may not be modified in this view, but it will maintain any sorting parameters the user has implemented in the List View table.

Figure 2. All available list view columns (left) and filter options (right)

Right panel: visualize exposure footprints

The right side of the Portal search results displays an AstroView panel, which is updated to display one of a few choices of sky-survey imaging of the target area overlaid with footprints of the search result images.  This panel is active (but can be hidden) and may be zoomed and panned; it will update in real time when filters of the search results are applied.  The user may even click individual footprints in this panel to select specific images in both the list and album views of the search results. 

Portal Catalog Viewer

The Portal Catalog Viewer tool enables visualizing source catalogs, including the Hubble Source Catalog (HSC; Whitmore et al. 2016), as positions distributed on a displayed image or as a user-defined plot of various source attributes. A number of tutorials have been developed for various science uses, and some are highly relevant for JWST data users.

Catalog cross-matchPerform cross-match between user catalog and the HSC
Catalog FilteringIsolate the red sequence in the galaxy cluster Abell 2390
Catalog filtering and outlier detectionSearch for variable objects in the dwarf irregular galaxy IC 1613
Outlier detection with the HSCSearch for white dwarfs in the globular cluster M4 using the HSC and the CasJobs engine

JWST engineering database portal

The JWST engineering database is an archive repository of engineering telemetry, or time-dependent status information about science instruments and the spacecraft itself. Telemetry associated with specific measurements, tagged with mnemonics, may be queried through the Engineering Database interface. You may access this interface in one of two ways:

  1. Direct your browser to the JWST Engineering Database Portal, or
  2. After a Portal search for science data, click the EDB icon in any row of the results table: 


Figure 3 below shows the interface as invoked after a search for NIRCam science data (in this case, simulated data). With such an invocation the time range is pre-populated to match the observation.

Figure 3. Interface for engineering database.

The Portal interface has separate panels for mnemonic selection (upper left), time range (lower left), and preview time series plot (right).

To view specific engineering data:

  • Enter a mnemonic of interest in the dialog box (upper left). Note that a list of available mnemonics that match the text in the dialog box appears in a selector below as you type.
  • Type or use the sliders to modify the time range (lower left) if desired. After entering a new time range, click the Add Date Range button.
  • Click the Run Query button (bottom left of panel)
  • Optionally invoke the plot tool by clicking the icon:
  • Optionally download the time series data as a CSV table by clicking the disk icon: 

See the tutorial: Search the Engineering Database for more details.  

You must have a MyST account and be logged in to query the Engineering database.

Community data visualization tools

Below is an incomplete list of community, VO-aware tools for visualizing and exploring archived astronomical images, spectra, and catalogs.

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
SpecViewAnalysis1-D spectrum visualization and analysis
TOPCATAnalysisCatalog cross-match, filtering, sub-setting, and visualization tool
VizieRRetrievalAstronomical catalog search engine
astropy.vo.clientDiscoveryPython packages for using VO services, including accessing VO registries, as well as catalog manipulation in software



Fleming, S. W., et al. 2015, AAS, 225, 336.59
Beyond the Prime Directive: The MAST Discovery Portal and High Level Science Products

Whitmore, B., et al. 2016, AJ, 151, 134
Version 1 of the Hubble Source Catalog

MAST Portal user manual

MAST Discovery Portal (web interface)

MAST JWST Engineering Database Portal



Latest updates
    Rewritten and expanded subsection on the JWST Engineering Database Browser