Predictions of Imminent Earth Impactors Discovered by LSST

Abstract

Imminent impactors are natural bodies discovered in space before impacting the Earth. They provide a rare opportunity to characterize individual near-Earth objects (NEOs) in great detail as asteroids in space, meteors in Earth's atmosphere and meteorites on the ground. The Vera C. Rubin Observatory's upcoming Legacy Survey of Space and Time (LSST) is expected to transform our understanding of the NEO population. In this work, we evaluate LSST's expected discovery performance for imminent impactors using $343$ meter-size objects previously recorded in NASA's CNEOS database as fireballs impacting Earth's atmosphere. We simulate pre-impact observations of these CNEOS impactors with the Sorcha survey simulator under LSST's default three-night discovery strategy and a one-night strategy for fast-moving objects that relies on matching aligned streaks in two exposures on the same night. We estimate that LSST will discover $\sim 1-2$ meter-size and larger imminent impactors per year, representing $\sim 4\%$ of all Earth impactors $\gtrsim 1$ m in diameter and almost doubling the current discovery rate of imminent impactors. The median time of discovery and median time of first observation for impactors discovered in our simulations are $\sim 1.57$ and $\sim 3.06$ days before impact, respectively. The spatial distribution of the 11 previously discovered imminent impactors is biased towards the Northern Hemisphere, where the observatories that discovered them are located. We find a similar trend towards Southern Hemisphere impacts in our simulated LSST detections of the CNEOS impactors, suggesting Rubin will provide a powerful counterpart to existing asteroid surveys primarily located in the Northern Hemisphere.

Accepted 2026 March 4 for publication in ApJ. 19 pages, 7 figures, 4 tables

References in corpus (19)

• Compositional distributions and evolutionary processes for the near-Earth object population: Results from the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS
• The Global Meteor Network -- Methodology and First Results
• Tuning the Legacy Survey of Space and Time (LSST) Observing Strategy for Solar System Science
• Two Strengths of Ordinary Chondritic Meteoroids as Derived from their Atmospheric Fragmentation Modeling
• Source regions of carbonaceous meteorites and NEOs
• Data on 824 fireballs observed by the digital cameras of the European Fireball Network in 2017-2018. I. Description of the network, data reduction procedures, and the catalog
• Orbital characterization of superbolides observed from space: dynamical association with near-Earth objects, meteoroid streams and identification of hyperbolic meteoroids
• The Albedo Distribution of Near Earth Asteroids
• The debiased compositional distribution of MITHNEOS: Global match between the near-Earth and main-belt asteroid populations and excess of D-type Near-Earth Objects
• Predictions of the LSST Solar System Yield: Near-Earth Objects, Main Belt Asteroids, Jupiter Trojans, and Trans-Neptunian Objects
• Atmospheric entry and fragmentation of small asteroid 2024 BX1: Bolide trajectory, orbit, dynamics, light curve, and spectrum
• Oort cloud perturbations as a source of hyperbolic Earth impactors
• Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defense
• Aperture photometry on asteroid trails: detection of the fastest rotating near-Earth object
• Decameter-sized Earth impactors -- I: Orbital properties
• Using neural networks to model Main Belt Asteroid albedos as a function of their proper orbital elements
• Error dependencies in the space-based CNEOS fireball database
• Site Selection for the Second Flyeye Telescope: A Simulation Study for Optimizing Near-Earth Object Discovery
• Decameter-sized Earth Impactors -- II: A Bayesian Inference Approach to Meteoroid Ablation Modeling