A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval
This study addresses the failure of simulation-based inference when applied to real James Webb Space Telescope (JWST) spectra, identifying that this breakdown stems from omitting planetary radius as a latent variable rather than from simulator inaccuracies. To resolve this, we propose MIRAGE, a framework that incorporates radius as a critical latent variable and integrates flow matching, optimal transport mappings, and importance sampling to rectify the inference pipeline, achieving physically consistent retrievals through nested sampling calibration. By reducing the goodness-of-fit metric from 301 to 0.06, our approach successfully demonstrates generalization across instruments and multiple targets, enabling end-to-end retrieval of real exoplanetary atmospheric data. This work reveals that latent variable misspecification, not simulator error, underlies prior inference failures, offering a robust methodology for future spectroscopic analyses.