# PandExo: A Community Tool for Transiting Exoplanet Science with JWST & HST

## TL;DR

PandExo is an open-source Python tool that simulates JWST and HST noise for exoplanet spectroscopy, aiding community planning and optimizing observations before launch.

## Contribution

It introduces PandExo, a community-accessible noise simulator for JWST and HST, validated against existing tools and observations, to support exoplanet atmospheric studies.

## Key findings

- PandExo's noise estimates agree within 10% with existing simulators.
- PandExo effectively models JWST and HST instrument noise for exoplanet spectroscopy.
- The tool facilitates planning and optimizing future exoplanet observations.

## Abstract

As we approach the James Webb Space Telescope (JWST) era, several studies have emerged that aim to: 1) characterize how the instruments will perform and 2) determine what atmospheric spectral features could theoretically be detected using transmission and emission spectroscopy. To some degree, all these studies have relied on modeling of JWST's theoretical instrument noise. With under two years left until launch, it is imperative that the exoplanet community begins to digest and integrate these studies into their observing plans, as well as think about how to leverage the Hubble Space Telescope (HST) to optimize JWST observations. In order to encourage this and to allow all members of the community access to JWST & HST noise simulations, we present here an open-source Python package and online interface for creating observation simulations of all observatory-supported time-series spectroscopy modes. This noise simulator, called PandExo, relies on some aspects of Space Telescope Science Institute's Exposure Time Calculator, Pandeia. We describe PandExo and the formalism for computing noise sources for JWST. Then, we benchmark PandExo's performance against each instrument team's independently written noise simulator for JWST, and previous observations for HST. We find that \texttt{PandExo} is within 10% agreement for HST/WFC3 and for all JWST instruments.