Probabilistic Spectral Reconstruction of Trans-Neptunian Objects from Sparse Photometry: A Framework for Taxonomy, Survey Optimization, and Outlier Detection

Abstract Near-infrared (near-IR) spectroscopy provides critical constraints on the surface composition of trans-Neptunian objects (TNOs), but spectroscopic observations remain limited compared to broadband photometry. We develop a probabilistic latent-space framework to quantify how much spectral information is retained in sparse photometric measurements. Using a principal component representation trained on a sample of near-IR spectra, we model the spectral manifold of TNOs and perform Bayesian inference in this reduced space to reconstruct full spectra from photometry while propagating measurement uncertainties. Leave-one-out cross-validation demonstrates that the dominant modes of spectral variability are low dimensional: approximately four to five principal components capture the structure relevant for taxonomic classification, while 8–10 components improve spectral reconstruction fidelity and uncertainty calibration. For most objects, the reconstructed spectra achieve empirical credible interval coverage of ∼95% across the wavelength. These results suggest that the diversity of near-IR spectral shapes in the current sample is governed by structured, correlated surface processes rather than stochastic variation. Practically, we apply this framework to survey optimization, quantifying the information content of JWST/NIRCam filters to identify optimally informative configurations (e.g., F090W, F115W, F410M, F460M) for future observations for TNO taxonomy. Additionally, we demonstrate the pipeline’s capability to detect and reconstruct rare spectral types, such as the peculiar Neptune Trojans 2006 RJ 103 and 2011 SO 277 , by allowing constraining photometry to select low-probability intermediate models from the continuous topological manifold. Ultimately, this framework bridges the gap between sparse photometry and spectroscopy, providing a statistically rigorous tool to map the compositional structure of minor planets in upcoming large-scale surveys.