A general guide to getting started with planning JWST observations is provided in this article. Please also refer to articles in the Methods and Roadmaps section for more method-specific roadmaps. The JWST Call for Proposals for Cycle 4 describes policy issues related to proposals and submissions.

Outline your observational strategy

1. Identify instrument(s) and observing mode(s) you'll need to address your science goals. Extensive documentation is available for all four of the instruments, namely the Mid Infrared Instrument (MIRI), Near Infrared Camera (NIRCam), Near Infrared Spectrograph (NIRSpec), and Near Infrared Imager and Slitless Spectrograph (NIRISS). The Methods and Roadmaps section summarizes JWST observing capabilities and provides step-by-step observing guides. You can also compare and contrast the unique observing modes of each instrument . 
   
   
2. Familiarize yourself with the documentation for your chosen instrument mode, paying particular attention to things such as:
   
   1. How to use MULTIACCUM detector readouts to specify the exposure time for your JWST observation.
      
   2. Whether operations such as dithering, target acquisition, mosaicking, etc., are required, encouraged, or not permitted for that mode
   3. Whether you should consider using a subarray for your observations
   4. Whether your chosen mode is multi-phase, e.g., the NIRSpec multi-object spectroscopy mode may require NIRCam pre-imaging to obtain high quality astrometry for your target list
      
   5. Depending on the details of your science and observational strategies, it may also be beneficial to learn more about the JWST observatory hardware and JWST observatory characteristics and performance.
      
      
3. Read the relevant articles listed in JWST Recommended Observing Strategies for your chosen instrument mode for advice on which observing parameters to pick to optimize your science program.

Use relevant observation planning tools 

1. Familiarize yourself with the main tools available for planning observations, namely the Exposure Time Calculator and the Astronomer's Proposal Tool. Depending on the details of your science and observational strategies, other available tools may also be useful or necessary. This includes the JWST Interactive Sensitivity Tool (JIST), JWST Backgrounds Tool, JWST Target Visibility Tools, Duplication Checking Tools, and WebbPSF, as described below.
   
   

2. Many of the tools have helpful video tutorials, which is a quick way get started!

   
   

3. Read through an example science program for your chosen instrument mode (if available) to see a complete overview of the proposal planning process, including how to construct an Exposure Time Calculator (ETC) workbook and complete an Astronomers Proposal Tool (APT) observing template.
   
   
4. If unsure about feasibility of your observing program, use the JWST Interactive Sensitivity Tool (JIST) for a quick estimate of the signal-to-noise value for a given source flux density and exposure time for your chosen instrument observing mode(s). Otherwise proceed directly to the more detailed Exposure Time Calculator (ETC) as described below.
   
   
5. If you are planning to observe particularly faint targets, assess whether your observations will be background limited. The JWST Backgrounds Tool will be helpful for determining how the background changes over time and how significantly the target visibility is constrained by this.
   
   
6. Targets that need to be observed at a particular time, time separation, or aperture position angle on the sky may have significantly constrained visibility or may even be unschedulable. This is because only approximately 40% of the sky is accessible to at any given time, even though the entire sky is available to JWST observations over the course of a year. Many calculations relevant to this are already integrated into APT, so use of the separate Target Visibility tools may be unnecessary for most users. However, these tools are sometimes useful to perform a quick assessment of schedulability of proposal targets prior to developing an APT proposal, and/or assess feasibility when there is a specific timing window or position angle needed for your target. There are more specialized tools to help users plan coronagraphy observations and pre-imaging observations for NIRSpec MOS mode.
   
   
7. Check whether your target(s) is already planned to be observed. Duplicate observations are allowed only under certain circumstances.
   
   
8. If detailed understanding of the point spread function (PSF) is critical for assessing the feasibility of your planned science observations, then it may be helpful to use WebbPSF, a Python tool for calculating simulated PSFs for most JWST instrument modes.

Use the Exposure Time Calculator to determine observing parameters

1. Words in bold are GUI menus/
   panels or data software packages; 
   bold italics are buttons in GUI
   tools or package parameters.

   The Exposure Time Calculator (ETC) should be used to determine the appropriate exposure parameters (e.g., Readout pattern, Groups per integration, Integrations per exposure, and Total Dithers) needed to achieve the desired signal-to-noise ratio for your target. Video tutorials and a new users guide to the ETC are available to help you get started with the ETC.
   
   
2. Define your source(s) and scene(s) in the ETC.
   
   
3. Select an instrument and observing mode in the ETC.
   
   
4. Select instrument parameters within the instrument configuration pane on the ETC calculations page.
   
   
5. Run an ETC calculation on your defined scene.
   
   
6. Adjust the exposure time via the Groups per integration, Integrations per exposure, and/or Total Dithers parameters until you obtain your desired signal-to-noise ratio (SNR):
   1. The instrument-specific observing strategies articles provide recommendations for how to split exposure time into Groups per integration, Integrations per exposure, and/or Total Dithers, based on observing mode, science use case, avoiding saturation, and minimizing cosmic ray hits on the detector.
   2. ETC batch expansion is an efficient way to determine the SNR for a range of possible values for a given exposure parameter.

Specify your observations in the Astronomers' Proposal Tool

1. The Astronomers' Proposal Tool (APT) is used to set up your observing program and submit your proposal. Training examples and video tutorials are available to help you get started.
   
   
2. Enter your proposed target(s) (or offset targets if required for your observing case). Note: for the special case of the NIRSpec multi-object spectroscopy mode, targets are not input directly, but are created by the NIRSpec MSA Planning Tool (MPT). If using this observing mode, make sure to read the extensive MPT documentation.
   
   
3. Define your observing parameters in the APT Observation Template(s) relevant for your chosen instrument(s) and observing mode(s). Here you would enter the exposure specifications (i.e., Groups per integration, Integrations per exposure, and/or Total Dithers) that you determined via the ETC. If desired, add cross references to your relevant ETC workbook in the "ETC wkbk. calc" field (strongly recommended if your program requires a target acquisition).
   
   
4. Make sure to define any special requirements (e.g., timing constraints, moving target, background limited observation).  
   
   
5. View an observation with the APT Aladin visualizer tool. Check whether or not your target is a challenging guiding field. Review the JWST Guiding Strategies and Challenging Fields article to mitigate the risks of guiding failures.
   
   
6. Run the Visit Planner to ensure your observations are schedulable, and resolve any errors. 
   
   
7. Run Smart Accounting to determine whether overheads associated with your program can be minimized.

Proposal completion and submission

For a detailed description of how to complete other APT fields, and to use the results of the preceding steps as part of the preparation and submission of a complete proposal, please refer to the JWST Call for Proposals for Cycle 4; in particular, look at JWST Proposal Workflow. JWST proposals follow a single-stream process. Please refer to directions on the aforementioned pages for situations in which it may not be possible to fully specify a proposal at the time of submission (e.g. to resolve all errors and warnings in APT).