WFI ETC Web Interface
The Roman WFI Exposure Time Calculator (ETC) Web Interface allows users to perform ETC calculations directly in a web browser. This article describes the main features of the Web Interface.
Software Freeze: To ensure a stable user experience, most Roman tools will not be updated during the Call for Proposals period. Users will be notified if any urgent fixes are released.
The web ETC no longer supports the MA table truncation
As of the R2025.9 version (released on September 15, 2025), the web ETC no longer supports truncation of the MA tables. If you need to explore shorter exposure times than what is available in the web ETC, you can still use the Pandeia engine to explore the MA table truncation options, but caution is needed when considering the truncation. More information about the MA tables can be found on the WFI MultiAccum (MA) Tables article.
What is the Roman WFI ETC Web Interface?
The Roman WFI Exposure Time Calculator Web Interface enables ETC calculations in a browser. This tool is largely based on the JWST ETC Web Interface and uses the Pandeia engine at its core to allows users to set up complex scenes and observations through an easy-to-use graphical interface. It also outputs plots and relevant metrics to help users assess the feasibility of their observations with the Roman WFI. The Roman ETC Web Interface was first released to the astronomical community in September 2024 and development will continue in preparation for the initial Roman call for proposals.
The Roman WFI ETC Web Interface can be accessed through this link: https://roman.etc.stsci.edu/
Additional information on the ETC Web Interface can also found on the JWST Exposure Time Calculator Overview.
Tips for the Roman WFI ETC Web Interface
How do I get started with the ETC Web Interface?
Below are two methods for those who want to begin using the ETC Web interface:
1. The 'Quick Start' icon on the ETC Web Interface page, shown in the Figure of the ETC Web Interface, will take you to a new Workbook and walk you through (with the blue dialogue boxes) setting up the ETC calculation with an observing mode of your interest. Once you are satisfied with the calculation, you can switch to 'Login' or 'Create Account' to save the workbook.
Figure of the ETC Web Interface
The top image is a screen capture of the main ETC Web Interface page showing the Quick Start button. The bottom image is a blue dialogue box that is initiated after clicking Quick Start. This box guides users through the workbook with instructions.
2. The 'Sample Workbooks' offer example workbooks that are curated to show various observing setups using the ETC. The Figure Showing the Sample Workbooks provides an image of the drop down menu for the Sample Workbooks. If you are not familiar with how to access the Sample Workbooks, please see the How do I access different workbooks once I am in a workbook? section.
In particular, sample workbooks representative of the Core Community Surveys and the Galactic Plane Survey are available from this menu.
Figure Showing the Sample Workbooks
How do I access different workbooks once I am in a workbook?
Once users are within a workbook and want to switch to a different workbook, they can access their other workbooks by clicking the account drop-down menu from the top right and selecting the first option (either your user ID or anon_#### if working anonymously). They can also click the name "Exposure Time Calculator" to go back to the landing page.
Figure Demonstrating Login Options
Do I have to log in to use the ETC Web Interface?
No, users can either work anonymously or log into the ETC Web Interface. However, if you are logged in, your work is saved after you log out and can be accessed in future sessions.
Can I share my ETC Web Interface work?
Yes, it is possible to share workbooks with collaborators. This is available only when logged in. Work done anonymously is lost after the user leaves the ETC Web Interface session. Users are therefore encouraged to log into their accounts to avoid losing their ETC Web Interface work.
I did not log in and am working anonymously. Can I still save my workbook?
Yes. If a user begins a workbook anonymously, they can switch to a log-in session and own the workbook at the end. However, once the anonymous user leaves the ETC Web Interface session, the workbook cannot be recovered.
What software performs the calculations for the ETC Web Interface?
The ETC Web Interface uses the Pandeia software to do all the calculations necessary.
For additional questions not answered in this article, please contact the Roman Help Desk.