Data Access Policy

Science data obtained from JWST will be released to the astronomical community following an exclusive access period, during which the principal investigating team enjoys exclusive scientific use. The duration of the exclusive access period depends upon the program. Access to data during this period is restricted to authenticated and authorized users.

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More about the data access policy

Access to and use of JWST science data is governed by a mission policy not unlike that adopted for HST. Science data obtained from JWST will be released to the astronomical community and the public following an exclusive access period (EAP). Access to archived data during this period is limited to authenticated and authorized persons, which generally consists of the principal investigator team. However, all archive users will, in general, be able to search and view metadata related to planned and executed observations at any time, even during the EAP. Pre-images, which are used to support NIRSpec target acquisition, as well as guide star data obtained during an observation, also have EAP protection.

Engineering data

JWST engineering data are also hosted at MAST, and are obtained contemporaneously with science data. Most engineering data are not restricted (except during observatory commissioning), and may be retrieved by any authenticated user (i.e., they must be logged in to MAST to retrieve these data).

Exclusive access period

The exclusive access period (EAP), during which the investigator team enjoys exclusive access to these data in MAST, allows the investigators who proposed the observations time to formulate and publish the scientific results of their program. This period applies at the data product level (rather than to a completed observing program), and begins the moment that individual exposures obtained from the spacecraft have been calibrated and made available in MAST. The duration of the exclusive access period depends in part upon the type of observing program used to obtain the data, as summarized in the Data Rights and Duplications section of the Call for Proposals for the current cycle. Some programs, whether by policy or choice, have a zero-length EAP.

Embargoed Data

Data obtained during JWST science commissioning, including Early Release Observations and Early Release Science (ERS) program exposures, will be embargoed for a limited period of time following the observation to verify the performance of the system and for the preparation of public outreach materials.

Principal investigators (PIs) have the option of waiving all or part of their exclusive access period; in certain limited cases the STScI director may grant a request for an extension. Note that all data, whether or not access is restricted within MAST, may be used by authorized JWST project staff for monitoring and diagnostic purposes. See the policy explained in the Data Rights and Data Dissemination article for details. Access to EAP data in MAST requires users to establish electronic credentials with STScI; browsing and retrieval of such data requires both authentication of the user credentials and authorization to access data from particular programs.

Granting access to EAP data

PIs of programs may authorize access to users for their data during the EAP period by navigating to the MyST Home screen (shown below) and selecting the Manage option. From there click the Manage Access to Exclusive-Access Science Data menu option, select your program, and enter the MyST email address of record for your colleague.

Archive registration

Investigator team members who wish to access data within the exclusive access period must have an STScI MyST account to establish electronic credentials to authenticate their identity. PIs and CoIs of JWST observing programs already have MyST credentials, which they used to submit their proposals for review, but team members added after proposal submission (e.g., post-docs or graduate students) will need to establish an account if one does not already exist. Investigator team members must also be authorized to access data from their programs. PIs will automatically receive such authorization, which they may also grant to any collaborator who is registered with the STScI MyST. 

Data for which the exclusive access period has expired may be retrieved anonymously from MAST. A MyST account is not required to search, view, explore with MAST tools, or retrieve data that have been released to the public.


It is important for investigators who publish scientific results based on MAST data to acknowledge the mission and (if applicable) the source of funding. The appropriate acknowledgement depends upon which data are used. See the appropriate acknowledgement for JWST data on the MAST Mission Acknowledgements page. This page also contains acknowledgements for all other missions hosted at MAST. 


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JWST Policy for Data Rights and Data Dissemination

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