Data identified with a search may be retrieved in a number of ways, including via the MAST Portal download manager, browser download, ftp, and with user software. The best method of retrieval is largely a matter of convenience. Only authenticated and authorized users may retrieve data within the exclusive access period.
Retrieving JWST science data from MAST
Science data that have been identified through a Portal search may be retrieved in a number of ways. The best method of retrieval is largely a matter of user convenience, although fulfilling requests for very large volumes of data on hard media requires special effort. Anonymous users may search for and retrieve public datasets in MAST without registering and without logging in, but only authenticated and authorized users may retrieve data within the applicable exclusive access period. See the Data Access Policy for details and information on data access restrictions.
Science data retrieval options
Users who have identified science data of interest within the MAST Data Discovery Portal may retrieve the files (or collections of files) using one of the methods summarized below. For detailed instructions, see the following tutorial:
This download (through the browser) is the quickest and simplest choice for single entries in the results table: simply click the disk icon in the table row corresponding to the entry of interest. It is also possible to save the search results table itself to a CSV file by clicking the file save icon; this allows preserving the results of a complex search (with, say, many applied filters) and later uploading to the Portal to reproduce the search.
The download basket is appropriate for retrieving multiple entries at once. The basket contents can be customized in the download manager to select specific product types (science, auxiliary, and preview), as well as the associated calibration reference files. There are two options for retrieval: immediate download through the browser, and staging data for later retrieval.
Immediate download: The selected data files will be bundled into a
.zip file and transferred to the user's machine.
Data retrievals via immediate download are limited to about 5 GB. Larger transfers require an asynchronous retrieval method: a cURL script, staging data for ftp retrieval, or the MAST API.
cURL script: A cURL script can be created and downloaded to the user's machine. Then simply execute the script in a Unix shell, and provide login credentials when prompted, to initiate the secure transfer of all selected files. Alternatively, users with poor internet connectivity may request data via hard media.
There are two methods of batch retrieval: staging data on the MAST ftp server for subsequent retrieval by the user, and having data written to hard media that is later shipped to the user. These options are summarized in Table 1, below.
Table 1. Batch retrieval methods
Note that a valid email address must be provided for all batch data retrieval requests, though an STScI MyST ID is not required for public data.
What's in the box
All data products for all selected observations will be bundled together for delivery. When the
.tar file is unpacked, data for each observation/visit/exposure/detector will appear in a separate subdirectory. For each subdirectory, the data bundle includes by default the highest-level data products, plus all parent data (unless those data have been de-selected in the download manager) For example, if an observation/visit/exposure/detector combination resulted in Level-2 data products, all Level-1 products would automatically be included unless the user explicitly chooses otherwise. Note: Level-3 products will appear in separate directories.
The download manifest
The zip (or tar) file will include a file called
MANIFEST.HTML which lists each file name, a short description, and whether access is restricted. It will also note any files that could not be downloaded and the reason why (e.g., if you do not have permission to retrieve them).
MAST portal download examples
The MAST programmatic API
It is possible to retrieve data using scripts in various programming languages, such as Unix shell scripts or Python, through the Mashup API for MAST. See Programmatic Interfaces for details.
A variety of community applications can retrieve data from astronomical archives, including MAST. These tools use Virtual Observatory protocols to discover and retrieve data files. Table 2. proviedes with a list of some of them.
Table 2. List of applications and cabilities
|Aladin||Sky atlas tool|
|SAOImage/DS9||Image and catalog display tool|
|TOPCAT||Catalog joins, subsetting, editing, and visualization|
|VizieR||Extensive VO catalog offerings|
|VOClient||Standalone software for querying and downloading VO data from USVAO|
These tools currently lack the ability to provide user authentication credentials to archive services, and so cannot be used to retrieve data archived within the exclusive access period.
VizieR retrieval examples