pyEDITH exposure calculator for HWO

Eleonora Alei and co-authors posted a paper on September 2 describing pyEDITH, a Python-based coronagraphic exposure time calculator for NASA’s planned Habitable Worlds Observatory. The paper says the software is meant to estimate wavelength-dependent exposure times and signal-to-noise ratios for direct imaging observations of exoplanets with a coronagraph. The Habitable Worlds Observatory, or HWO, is the mission concept identified in the Astro2020 decadal survey as NASA’s next flagship observatory for finding and characterizing potentially habitable worlds. (arxiv.org) ### What exactly did the researchers release? The September 2 paper describes pyEDITH as a software tool rather than a new instrument. The authors say it is designed to simulate coronagraphic observations across photometric bandpasses and spectroscopy modes, with outputs that can be used for target characterization, observing strategies and mission trade studies. The project is also live as usable software. The pyEDITH documentation says the package includes functions for exposure-time calculations, signal-to-noise estimates and conversions between the two, and the GitHub repository lists command-line tools labeled `etc`, `snr` and `etc2snr`. (arxiv.org) ### Why does HWO need an exposure-time calculator? A 2025 cross-model validation paper said exposure times sit at the center of HWO science planning, from exoplanet yield estimates to atmospheric spectral retrievals. (arxiv.org) That paper said multiple teams had been comparing coronagraphic exposure-time calculators because the mission’s expected scientific return depends on how long the observatory would need to stare at faint targets. The HWO technology development material says the mission is being designed to search for and characterize habitable exoplanets while also serving broader astrophysics goals. (pyedith.readthedocs.io) In that setting, software that estimates observing time helps planners compare instrument settings, target lists and science priorities before a telescope is built. ### What kinds of planets and observations does pyEDITH cover? The arXiv abstract says pyEDITH is built to estimate integration times for Earth-like and Neptune-like targets. (arxiv.org) The paper says the tool can simulate both photometric observations and spectra, which makes it relevant for first-pass detection work as well as follow-up characterization. The documentation says pyEDITH computes wavelength-dependent exposure times and signal-to-noise ratios, which are the quantities observers use when deciding whether a given bandpass, spectral resolution or target brightness is practical within a mission schedule. (astrobiology.com) That makes the code a planning tool for questions such as how long HWO would need to observe a nearby exoplanet to detect specific reflected-light features. ### Who is behind the project? The arXiv listing names Eleonora Alei, Miles H. (arxiv.org) Currie, Corey Spohn, Christopher C. Stark, Aki Roberge, Avi M. Mandell, Enrico Biancalani, Samantha Gilbert-Janizek, Jacob Lustig-Yaeger and Sarah Steiger as authors. Several of those researchers have also appeared on recent HWO methods papers tied to coronagraph operations, biosignature observing requirements and exposure-time validation efforts. The GitHub repository is published under the HabitableWorldsObservatory organization, and the documentation is already available publicly. (pyedith.readthedocs.io) That suggests the team intends pyEDITH to be used by the broader HWO planning community, not only by the paper’s authors, though the paper does not state a formal release roadmap beyond the current public version. ### Where does this fit in the HWO timeline? NASA’s HWO planning work is still in the mission-definition and technology-development stage. (arxiv.org) The July 2026 HWO technology development plan says the observatory is NASA’s next large space telescope concept and ties the effort to the Astro2020 recommendation. For now, the next concrete step is public use and scrutiny of the software itself. The paper is available on arXiv, and the code and user documentation are already posted through the project’s repository and documentation site for researchers working on target selection, spectroscopy planning and mission trade studies. (github.com) (arxiv.org) (astrobiology.com)