AION-1: Omnimodal Foundation Model for Astronomical Sciences

Liam Parker; Francois Lanusse; Jeff Shen; Ollie Liu; Tom Hehir; Leopoldo Sarra; Lucas Meyer; Micah Bowles; Sebastian Wagner-Carena; Helen Qu; Siavash Golkar; Alberto Bietti; Hatim Bourfoune; Nathan Casserau; Pierre Cornette; Keiya Hirashima; Geraud Krawezik; Ruben Ohana; Nicholas Lourie; Michael McCabe; Rudy Morel; Payel Mukhopadhyay; Mariel Pettee; Bruno Regaldo-Saint Blancard; Kyunghyun Cho; Miles Cranmer; Shirley Ho

arXiv · 2510.17960

AION-1: Omnimodal Foundation Model for Astronomical Sciences

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Abstract

While foundation models have shown promise across a variety of fields, astronomy still lacks a unified framework for joint modeling across its highly diverse data modalities. In this paper, we present AION-1, a family of large-scale multimodal foundation models for astronomy. AION-1 integrates heterogeneous imaging, spectroscopic, and scalar data using a two-stage architecture: modality-specific tokenization followed by transformer-based masked modeling of cross-modal token sequences. The model is pretrained on five large-scale surveys: Legacy Survey, Hyper Suprime-Cam (HSC), Sloan Digital Sky Survey (SDSS), Dark Energy Spectroscopic Instrument (DESI), and Gaia. These span more than 200 million observations of stars, galaxies, and quasars. With a single frozen encoder, AION-1 achieves strong results on a broad suite of downstream tasks, including galaxy and stellar property estimation, galaxy morphology classification, similarity-based retrieval, galaxy image segmentation, and spectral super-resolution. We release AION-1 model variants ranging from 300 M to 3.1 B parameters. Beyond astronomy, AION-1 provides a scalable blueprint for multimodal scientific foundation models that can seamlessly integrate noisy, instrument-specific observations. All code, tokenizers, pretrained weights, and a lightweight evaluation suite are released under an open-source license.

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Liam Parker, Francois Lanusse, Jeff Shen, Ollie Liu, Tom Hehir, Leopoldo Sarra, Lucas Meyer, Micah Bowles, Sebastian Wagner-Carena, Helen Qu, Siavash Golkar, Alberto Bietti, Hatim Bourfoune, Nathan Casserau, Pierre Cornette, Keiya Hirashima, Geraud Krawezik, Ruben Ohana, Nicholas Lourie, Michael McCabe, Rudy Morel, Payel Mukhopadhyay, Mariel Pettee, Bruno Regaldo-Saint Blancard, Kyunghyun Cho, Miles Cranmer, Shirley Ho. 2025-10-20. AION-1: Omnimodal Foundation Model for Astronomical Sciences. https://arxiv.org/abs/2510.17960

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