Error dependencies in the space-based CNEOS fireball database

TL;DR

This study assesses the reliability of the CNEOS space-based fireball database, identifying key factors affecting data accuracy and highlighting improvements over time, while cautioning about hyperbolic event interpretations.

Contribution

The paper provides a detailed analysis of error dependencies in CNEOS fireball data, introducing discriminants for accuracy and showing data quality improvements since 2018.

Findings

CNEOS data accuracy improved after 2017, especially for high-energy fireballs.

Two main groups of data accuracy are identified based on $D_D$ values.

Hyperbolic fireball candidates are likely measurement errors, not true hyperbolic trajectories.

Abstract

We evaluate the reliability of CNEOS-derived ephemerides of fireball events given the absence of the underlying data. We analyzed 18 events that have both (i) sufficient satellite information to derive orbits and (ii) ground-based observational counterparts. We quantify the uncertainties on these calibrated events using the orbital similarity criterion $D_D$. We also examine the velocity components imbalance and identify discriminants that can indicate the accuracy of an event. We identify two groups in the CNEOS database. CNEOS data produces ephemeris determinations with $D_D$<0.1 for fireballs reported either (i) after late 2017 or (ii) with impact energies above 0.45 kt with 74-78% of events having $D_D$=0.03$\pm$0.02, while ~11% show $D_D$<0.008. Our statistical test confirms these two parameters as the only reliable discriminants that, when combined, explain the two accuracy groups. Daylight, z-velocity component, low altitude, long duration, and latitude might also indicate errors, although the limited dataset may obscure correlations. No clear discriminants are identified for more restrictive $D_D$ cut-offs. We provide estimates of orbital uncertainties for calibrated events. The hyperbolic fireball subset in the CNEOS database appears as an outlier in the velocity imbalance test. Our results confirm that the fidelity of CNEOS fireball data improved significantly from 2018, likely due to the deployment of next-generation space sensors, and show a growing number of high-velocity events. Hyperbolic candidates should be interpreted with caution, as their velocities and inclinations likely reflect measurement errors. Accuracy constraints remain limited by the dataset size, as evidenced by the lack of statistically significant dependence on duration, preventing strong conclusions from being drawn.