POSEIDON models and retrieves 1D, 2D, and 3D exoplanet transmission spectra. Given a set of observed exoplanet spectra from space-based or ground-based telescopes, the code uses Bayesian techniques to infer the atmospheric properties of the planet. POSEIDON also includes disk-integrated thermal emission and reflection spectra modeling and retrievals for both secondary eclipses and directly-imaged substellar objects.

JexoSim 2.0 (JWST Exoplanet Observation Simulator) simulates exoplanet transit observations using all four instruments of the James Webb Space Telescope, and is designed for the planning and validation of science cases for JWST. The code generates synthetic spectra that capture the full impact of complex noise sources and systematic trends, allowing for assessment of both accuracy and precision in the final spectrum. JexoSim does not contain all known systematics for the various instruments, but is a good starting point to investigate the effects of systematics, and has the framework to incorporate more systematics in the future.

BART implements a Bayesian, Monte Carlo-driven, radiative-transfer scheme for extracting parameters from spectra of planetary atmospheres. BART combines a thermochemical-equilibrium code, a one-dimensional line-by-line radiative-transfer code, and the Multi-core Markov-chain Monte Carlo statistical module to constrain the atmospheric temperature and chemical-abundance profiles of exoplanets.