General Proposal Planning Workflow
A roadmap of general instructions for planning JWST observations. See method-specific roadmaps for more detailed information about individual observing modes.
The steps below suggest a general workflow, but depending on your science goals and background, the steps and order may vary.
Become familiar with JWST capabilities and terminology
- Be sure to read through the Call for Proposals and familiarize yourself with JWST Science policies.
- Learn about MULTIACCUM detector readouts to understand how to specify the exposure time for your JWST observation.
- Identify instrument(s) and observing mode(s) you need to address your science goals. The observing methods articles summarize the observing methods offered by JWST, and compare and contrast the unique observing modes from each instrument that support these different types of observations. Mode-specific roadmaps are also available.
- Familiarize yourself with the documentation for your chosen instrument mode, paying particular attention to:
- 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;
- whether operations such as dithering, target acquisition, mosaicking, etc., are required, encouraged, or not permitted for that mode;
- whether you should consider using a subarray for your observations.
- Read the JWST Recommended Observing Strategies for your chosen instrument mode for advice on which observing parameters to pick to optimize your science program.
- 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.
Determine if your targets can be observed
- Check whether your target(s) is already planned to be observed. Duplicate observations are allowed only under certain circumstances.
- If there is a specific window in which you need to observe your target, use the Visibility Checker to ensure that the target is visible by JWST during that window.
- If you are planning to observe particularly faint targets, assess whether your observations will be background limited. The Backgrounds Tool will be helpful for visualizing how the background changes over time and how significantly the target visibility is constrained by this.
Use the Exposure Time Calculator to determine observing parameters
- The Exposure Time Calculator (ETC) should be used to determine the appropriate exposure parameters (e.g., READOUT PATTERN and NUMBER OF GROUPS, INTEGRATIONS, and EXPOSURES) needed to achieve the desired signal-to-noise ratio for your target. Video tutorials and a new user guide for the ETC are available to help you get started with the ETC.
- Define your source(s) and scene(s) in the ETC.
- Select an instrument and observing mode in the ETC.
- Select instrument parameters within the instrument configuration pane on the ETC calculation page.
- Run an ETC calculation on your defined scene.
- Adjust the exposure time via the NUMBER OF GROUPS, INTEGRATIONS, and/or EXPOSURES until you obtain your desired signal-to-noise ratio (SNR):
- The instrument-specific observing strategies provide recommendations for how to split exposure time into NUMBER OF GROUPS, INTEGRATIONS, and EXPOSURES, based on observing mode, science use case, avoiding saturation, and minimizing cosmic ray hits on the detector.
- ETC batch expansion is an efficient way to determine the SNR for a range of possible values for a given exposure parameter.
Prepare your proposal in the Astronomers' Proposal Tool
- 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.
- Fill out your proposal information in APT, e.g., Title, Abstract, Proposal Category, Science Keywords, etc.
- 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.
- 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., NUMBER OF GROUPS, INTEGRATIONS, and EXPOSURES) 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).
- Make sure to define any special requirements (e.g., timing constraints, moving target, background limited observation).
- Run the Visit Planner to ensure your observations are schedulable, and resolve any errors.
- Run Smart Accounting to determine whether overheads associated with your program can be minimized.
- Complete and attach the PDF of your science justification to your APT template.
- If APT reveals no errors with your observing program, submit your proposal!