Data Exploration

Introduction

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 such as those for viewing areas of digital sky surveys, selecting images and footprints from popular missions and surveys, cross-matching and plotting source catalogs, and viewing timeseries of selected targets enable Archive users to plan JWST observing programs, and to place JWST new observations in the context of the extant astronomical data from around the world.

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 (DP), but there are also many additional tools available from the community at large. These tools enable users to plan JWST observing programs, explore JWST data once the observations are available in the Archive, and understand 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 MAST DP 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

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.  The user is also given the ability to 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.

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, etc.), mission (HST, SWIFT, FUSE, etc.), instrument, filters, waveband (optical, UV, infrared, etc.), principal investigator, calibration level, exposure length, start / end time, and several others.  These filters can accommodate a wide range of specific requests and combinations of constraints for narrowing down a large set of search results.

The List View in the middle of the results page provides a search results table with detailed information for all current search results after the application of any filters the user has selected.  Each column in the table may be used to sort the results as the user wishes, and the columns themselves may be customized 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, the user may also 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)

The right side of the MAST Portal search results displays a built-in AstroView panel, which is updated to display the STScI Digitial Sky Survey (DSS) imaging of the target area overlaid with footprints of the search result images.  This panel is active and may be zoomed and panned as the user wishes, and will update in real time as the user filters out various search results.  The user may even click on individual footprints in this panel to select specific images in both the list and album views of the search results.  The AstroView panel also provides some settings options for customizing aspects of the display, such as display of the given search radius, and RA/Dec grid lines.

DP Catalog Viewer

The DP 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.

TutorialDescription
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 Browser

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 a Portal interface. You may access this interface in one of two ways:

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

(The link to the EDB will be provided once there are public data available.) 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 timeseries 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 data as a CSV table by clicking the disk icon: 

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

The resulting preview, shown in Figure 4 below, is a timeseries plot of a sensor temperature. The plot is generated by R statistical software.

Figure 4. Telemetry 30-min timeseries for a MIRI sensor temperature.

Telemetry points are plotted with red dots, the blue areas are smoothed color density representations of the plot (darker areas correspond to higher density), and the yellow curve is a fit to the data using local polynomial regression fitting.

Community data visualization tools

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

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References

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




Last updated

Updated March 12, 2018

  • Rewritten and expanded subsection on the JWST Engineering Database Browser


Published July 11, 2017