Frequently Asked Questions - JWST First Data Release

Performance of MAST services or downloads is slow or not responding for me.

Especially during the first week or two we expect traffic to be much higher in a condensed period of time than usual.  To help with this, we hvae created bulk download scripts for the ERO programs, Highlighted Commissioning datasets, and all Commissioning datasets. These scripts download data from Amazon cloud straight to your machine.  They are used with no cost to you, and require no account of any kind.  We strongly recommend you use these bulk download scripts to retrieve ERO and Commissioning data sets, rather than attempt large downloads through the MAST Portal, astroquery.mast, or other mast.stsci.edu addresses.

I'm not able to download public data through the MAST Portal, API, or astroquery.mast.

For the first couple days, many files need to migrate from "exclusive access" to "anonymous access".  While that migration happens, some data sets might be marked as public based on their Release Date, but have not completed this migration.  If that is the case, you will not be able to download the data if you are not signed in to your STScI account (i.e., "anonymous access").  Instead, you can:

• use the AWS Bulk Download Scripts for ERO programs and Commissioning data to retrieve data through Amazon cloud
• sign in to your STScI account and then download the data
• wait until the migration process finishes (for ERO most data will be migrated in ~5 hours, for Commissioning it will take ~48 hours)

Note that this is not a common occurrence, it is an artifact of holding up large amounts of data to support Commissioning and ERO week.  For normal operations where data is released continuously, the migration process is not a limiting factor.

I am a PI of a (partially) executed JWST program.

When can I get my data?

Cycle-1 data will appear in MAST beginning on 14 July. See the Data Release Timeline for details.

How do I authorize my Co-Is to have access to data from that program?

Direct your browser to the MyST site, and follow the instructions in the MAST User Accounts article in the Portal Guide.

How do I learn which JWST observations have been obtained?

There are multiple ways to discover JWST Observations. For instance:

• To be notified when JWST data appear in the archive, become available to all users, or are reprocessed, use the subscription service in the MAST Portal.  This is the recommended way to find out when data from program IDs get ingested or receive updates.
• In the MAST Portal, click Advanced Search, enter "JWST" in the Mission filter and enter a start date, e.g., "2022-07-02" in the Start Time filter, then click the Search button.
• Using the Python library astroquery.mast, form a query_criteriasearch with the parameters obs_collection="JWST" and some other parameter such as instrument_name="MIRI" . See the astroquery.mast documentation for details.

What is the usual delay between the end of an observation and when it first appears in MAST?

That is a difficult question to answer with precision. A lot of the data gets processed within an hour or two, but there are a few edge cases where it takes more than a day. But that’s after the data processing system gets all of the pieces from Flight Operations. Many hours can elapse between the end of an exposure and transmission of that data to the ground. This is largely because JWST does not have continuous contact with the ground in the high-bandwidth channel that is required to transmit high-volume science data. That said, it is likely that most data will appear in MAST within a day or two of the end of the last exposure in an observation. 

JWST Generates so many files. Which ones are most important?

Generally the Level-2b (calibrated) and Level-3 (calibrated and combined) products are most appropriate for science analysis. Consult the JDox article Getting Started with JWST Data for details.

I'm writing a paper that analyzes data from JWST. How do I create a DOI to reference the data I used?

Navigate your browser to the special DOI Portal. Follow the instructions in the Special Searches article in the Portal Guide, specifically the section on Create a DOI.

Primary Reference Sources

• JWST User Documentation Home (JDox)
• JWST Archive Manual
• MAST Portal Guide

For Further Help...

• JWST Help Desk: https://stsci.service-now.com/jwst (requires login)
• MAST Help Desk: https://stsci.service-now.com/mast (requires login)