A Director's Discretionary Time (DDT) proposal is appropriate when a truly unexpected transient phenomenon occurs or when developments since the last proposal cycle make a time-critical observation necessary. The pool of JWST time for in-cycle DD proposals is limited and typical proposals are less than 8 hours, although larger requests can be considered under exceptional circumstances.

Starting in Cycle 2, joint JWST-HST DD proposals are permitted. Proposals should be submitted to the observatory with the larger time request. Joint DD proposals with other facilities are not permitted.

Observations obtained as part of a DD program generally do not have an exclusive access period, and are made available immediately to the astronomical community. However, DD proposers may request and justify such periods in their proposals. Such requests will only be granted under exceptional circumstances. Upon receipt of a DD Proposal, the STScI Director will usually seek advice on the scientific merit and technical feasibility of the proposal from STScI staff and external specialists.

At present, only time-critical JWST DDT proposals will be considered. Additional information is available at Director's Discretionary (DD) Time Proposals.

Check back in the future for other DD proposal opportunities.

Large-scale DD initiatives

STScI Directors have used substantial portions of DD time, on occasion, for major scientific initiatives. The prototype for this use of DD time was the Hubble Deep Field observations in 1994, a revolutionary set of observations that had enormous impact on the course of astronomy, and on the public imagination. These observations were followed up on Hubble with similar campaigns for the Hubble Deep Field South, the Ultra Deep Field, the WFC3 Early Release Science programs, the Frontier Fields, and ULLYSES. 

On JWST, the Director's Discretionary (DD) Early Release Science (ERS) Program was established to help maximize the science return. To increase the number and breadth of JWST observations that are public in time for GO Cycle 2 proposal preparation, the Director allocated 530 hours of Cycle 1 DD time to 13 community-led ERS programs. The majority of these observations, encompassing a wide range of science cases, instruments and observing modes, will be acquired in the first 5 months of science operations and become public immediately. The ERS teams are working hard to produce product deliveries shortly after data acquisition, including high-level data products, software tools, Jupyter notebooks, documentation, instrument performance, simulations, ancillary data, and community engagement events.