JWST Cycle 1 Single-Stream Proposal Process

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JWST proposals are submitted via a single-stream process through the Astronomer's Proposal Tool, where all information about the proposed science and observations are provided up front at the time of submission.

Proposal process

For most proposals, JWST follows a "single-stream" approach where a single submission is made for each proposal by the deadline.  A single-stream process for JWST proposal submission has been adopted for three reasons: 

  1. Similar to Spitzer, JWST visits will be continuously scheduled in an event-driven process, as opposed to discrete orbits. JWST proposers must therefore specify more information up front than Hubble proposers so that the total time required for an observing program can be determined and made available to the TAC. This includes accounting for slews and instrumental overheads that are often hidden from Hubble observers since they occur during Earth occultation. 

  2. For cycle 2 and beyond, a single-stream process minimizes the time between proposal deadlines and the start of an observing cycle, as it is expected that only certain classes of proposals may be revised after submission. This, in turn, maximizes the amount of JWST data that is available when the subsequent round of proposals is written, thus accelerating the intellectual cycle as new discoveries guide the direction of new JWST observations. Cycle 1, however, is the exception because proposal submission occurs well before JWST launch and commissioning. In this case, a single-stream submission allows a longer and more thorough review of accepted proposals and more opportunities to provide support to successful proposers. 

  3. A “single-stream” approach enables the rapid construction of the long range plan (LRP). This helps to quickly incorporate accepted proposals into the scheduling system and allows to promptly assign execution position angles to observations that need these constraints (e.g. all NIRSpec MSA-based observations). 

The proposal system has been developed to enable users to, in most cases, enter essentially complete proposals at initial submission. Accepted proposals can then flow directly into the scheduling system with little delay. This is similar to the process at other space observatories such as Spitzer and Chandra, but differs from the two-step proposal system familiar to HST users. Note that this single-stream process is independent from the budget proposal process. Successful proposers will still have to submit a budget in line with the eligibility requirements, see JWST Cycle 1 Proposal Policies and Funding Support.

Proposers should be aware that they may need or wish to modify their accepted proposals based on the results of the JWST commissioning process. Proposers will be contacted by STScI should the need arise to modify a proposal. After acceptance of a proposal, proposers may wish to make minor changes (such as different dither patterns, guide stars, or readout modes). These changes should be discussed with the assigned program coordinator or instrument scientist. 


Submitted proposals must include sufficient information to define scheduling constraints for all visits (where each visit is directed at a specific target). Astronomers will submit their observing requirements using a set of templates for specific instrument modes. These templates are available in the Astronomer's Proposal Tool (APT). The submitted observing requirements include a full list of targets, specifications of the observations (instruments, filters, exposure times, dithers, observational sequence), and all user-requested scheduling constraints (including roll angle and other timing constraints). Complete APT files are required at submission so that APT can compute the direct overhead duration, which is defined by the sum of slews, the guide star and target acquisitions, mechanism motions, and small angle maneuvers, which are summed together to determine the total instrument overheads. 

In a few cases, APT may issue warning flags when APT template values are not adequately determined, or when it is not possible to fully determine whether a proposal is schedulable. Even in those cases, the complete APT file will contain sufficient information to estimate direct overheads and observing constraints. If this program is accepted, a program coordinator or instrument scientist will address these issues prior to scheduling. Generally, APT will generate a TAC review report that does not contain any technical flags.

Proposals may be submitted with warning flags, although proposers are strongly encouraged to resolve as many issues as possible. For proposals with errors, contact the JWST Help Desk to resolve them before submission. 


Proposals that cannot be fully specified at the time of submission are exempted from the single-stream process described above.  Details on the types of proposals that are exempted and the kind of information that is required for submission are specified in JWST Cycle 1 Special Submission Requirements. Note that these exceptions partly depend on APT functionality (expected to evolve with time) and therefore these special requirements might change from one Call to another. 

How APT can help

Several strategies are being employed to help JWST users prepare APT files for initial proposal submission.  Training materials and demo proposals can be found in the APT Help page in JDox

Observation templates in APT

In APT, once a user selects an instrument and an observing mode, the APT GUI changes to show only those parameters that need to be set for that mode. Each instrument and mode combination thus has an observation template format specific for that mode. Note: coordinated parallels require two instrument mode definitions in the same observation template. Once the relevant parameters for that observation have been specified, the template is complete and ready for further processing. Each instance of a template represents a single observation (although an observation may have one or many visits encoded within that observation, a process that is handled automatically for the user).

Schedulability and guide star availability checks

Using APT, a proposer must carry out guide star and schedulability checks, verifying that the observations are schedulable given the specified constraints. When one or more templates have been filled out, the user runs the Visit Planner step in APT. This important step executes a range of checks that look into the schedulability of the proposed observation(s). In addition to observatory viewing constraints, this check also assesses the availability of guide stars as a function of time, thus producing valid windows where the observation can schedule. The proposer may not choose specific guide stars or exact scheduling windows, as the schedulers need flexibility to prepare the most efficient LRP. If no guide stars are available for a given observation, the proposer may still submit the proposal for review; STScI staff will work with the team to determine whether mitigation is possible if the proposal is recommended for approval.

Minimization or elimination of time-consuming optimization steps

APT is tasked with nearly all of the "heavy lifting" in the proposal process. The user specifies observations, and if the proposed observations require many visits to be performed, this is handled internally in APT, by breaking the observations into visits as necessary, performing the relevant accounting of overheads through Smart Accounting, and reporting the results back to the user. (An HST user may be familiar with the phase II process of trying various combinations, or ordering of their proposed observations to make best use of their orbit allocation. None of that will be required for JWST).

Next: JWST Cycle 1 Special Submission Requirements

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