Abstract
Amortized simulation-based inference (SBI), which is trained on radiative-transfer simulators, recovers exoplanet atmospheres accurately on synthetic James Webb Space Telescope (JWST) spectra but collapses when it comes to real reduced spectra. The flow posterior collapsed on real WASP-39b (importance-sampling effective sample size (ESS) = 1, best-fit \c{hi}2/N = 301), and such a failure is usually blamed on missing the forward-model physics, but ruling these levers out with nested sampling first (a temperature gradient, SO2 opacity, and a high-fidelity opacity set) leaves the fit unchanged, meaning the collapse is not from the simulator misspecification but instead from a missing latent, the planet radius. To fix this, we build MIRAGE, a radius-augmented flow-matching posterior calibrated against an independent nested-sampling reference with importance sampling and an optimal-transport map, which yields a physical and literature-consistent retrieval of real WASP-39b (with \c{hi}2/N from 301 to 0.06). This same method transfers unchanged across two instruments and three real JWST targets, including one spectrum self-reduced end-to-end from raw Mikulski Archive for Space Telescopes(MAST) data. The lesson is cross-domain, as a latent the simulator encodes but the inference omits can masquerade as misspecification.
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Cite this article
APA 7
Chakravertty, A., & Raj, P. V. V. (2026). A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval. https://omanscience.com/en/articles/a-missing-latent-not-a-missing-simulator-radius-augmented-inference-for-real-jwst-retrieval
MLA 9
Chakravertty, Angshuman, and P V V Raj. "A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval." https://omanscience.com/en/articles/a-missing-latent-not-a-missing-simulator-radius-augmented-inference-for-real-jwst-retrieval.
Chicago (author–date)
Chakravertty, Angshuman, and P V V Raj. 2026. "A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval." https://omanscience.com/en/articles/a-missing-latent-not-a-missing-simulator-radius-augmented-inference-for-real-jwst-retrieval.
Harvard
Chakravertty, A. and Raj, P. V. V. (2026) 'A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval', Available at: https://omanscience.com/en/articles/a-missing-latent-not-a-missing-simulator-radius-augmented-inference-for-real-jwst-retrieval.
Vancouver
Chakravertty A, Raj PVV. A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval. https://omanscience.com/en/articles/a-missing-latent-not-a-missing-simulator-radius-augmented-inference-for-real-jwst-retrieval
IEEE
A. Chakravertty, and P. V. V. Raj, "A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval," https://omanscience.com/en/articles/a-missing-latent-not-a-missing-simulator-radius-augmented-inference-for-real-jwst-retrieval.