![5
The Aegis software
Aegis [1]
Asteroids Orbit Determination and Impact Monitoring
In Greek mythology Aegis is the shield used by Zeus. The Aegis
was said to be imbued with divine power and was depicted as a
shield adorned with the head of a Gorgon, Medusa.
[1] Fenucci et al. (2024). The Aegis orbit determination and impact monitoring system and services of the ESA NEOCC web portal, CMDA 136:58
Development Operations Evolution](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-5-320.jpg)
![6
Orbit Determination
Observations: ri i = 1, ..., m
Prediction function:
Residuals:
Target function:
Dynamical model:
Gravitational attractions
General Relativity
Earth and Sun J2
Non-gravitational effects
[2] Milani & Gronchi (2009). Theory of Orbit Determination
[3] Veres et al. (2017). Statistical analysis of astrometric errors for the most productive asteroid surveys, Icarus 296
[4] Farnocchia et al. (2015). Star catalog position and proper motion corrections in asteroid astrometry, Icarus 245
[5] Carpino et al. (2003). Error statistics of asteroid optical astrometric observations, Icarus 166
Fig. 4. Massive main belt asteroids included in the dynamical model.](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-6-320.jpg)
![9
Impact Monitoring
Summary of the algorithm [6]:
Line of Variations (LOV) sampling of the uncertainty
region
LOV propagation for 100 years
Analysis of returns on the Target Plane (TP)
Virtual Impactors (VI) search
Impact probability (IP) computation
Completeness limit: IP ~ 10-7
Fig. 7. Schematic representation of the target plane [7].
[6] Milani et al. (2005). Nonlinear impact monitoring: line of variation searches for impactors, Icarus 173
[7] Farnocchia el al. (2019). Planetary encounter analysis on the B-plane: a comprehensive formulation, CMDA 131](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-9-320.jpg)
![18
Recent research work supported by Aegis
Automated Yarkovsky effect detection [8]
• da/dt predicted by physical model
• da/dt computed by orbit determination
• Outlier identification:
• Statistical test with prediction
• Dependency on isolated tracklets
• 368 positive detections
• Data on NEOCC portal
[8] Fenucci et al. (2024). An automated procedure for the detection of the Yarkovsky effect and results from the ESA NEO Coordination Centre, A&A 682, A29
Fig. 10. Distribution of Yarkovsky effect detections
as a function of the diameter [X], with outliers.](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-18-320.jpg)
![19
Recent research work supported by Aegis
[9] Fenucci et al. (2025). Astrometry, orbit determination, and thermal inertia of the Tianwen-2 target asteroid (469219) Kamo`oalewa, A&A
[10] Novaković and Fenucci (2024). ASTERIA – Asteroid thermal inertia analyzer, Icarus 421
Kamo`oalewa, target of the Tianwen-2 mission [9]
• New observations from Loiano and Calar Alto (2024)
• Yarkovsky effect detection with SNR ~ 14
• Estimation of thermal inertia through ASTERIA [10]
• Regolith grain size extrapolation
Fig. 11. Conductivity (left) and thermal inertia (right) distribution of Kamo`oalewa obtained with ASTERIA.
Loiano](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-19-320.jpg)
![20
Recent research work supported by Aegis
Ab initio strewn fields [11]
• Entry point at 100 km altitude
• Single fragmentation model through atmosphere
• Drag force and wind modeling
• Reproduced cases of 2008 TC3, 2023 CX1 and 2024 BX1
The fall of 2024 XA1 [12]
• Impact predicted by ESA Meerkat [13]
• Impact point uncertainties at 100 km altitude
• Almost-live and final ab initio strewn field
[11] Carbognani et al. (2025). Ab initio strewn field for small asteroid impacts, Icarus 425
[12] Gianotto et al. (2025). The fall of asteroid 2024 XA and the location of possible meteorites, Icarus 433
[13] Gianotto et al. (2024). Meerkat asteroid guard–ESA’s imminent impactor warning service, 2nd NEO and Debris Detection Conference
Fig. 12. Entry of 2024 XA1 (top) into the
atmosphere and predicted strewn field (bottom).](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-20-320.jpg)
![21
Recent research work supported by Aegis
[14] Cano et al. (2025). Asteroid detection polar equation calculation and graphical representation, A&A 693, A183
Detection polar equation [14]
• Level surfaces for visual magnitude
• Helps in analyzing observability
• Nice visualization in the NEO Toolkit
Synodic Orbit Visualization Tool (SOVT)
• Catalogued and custom objects
Fig. 13. Detection polar (yellow) and orbit of Kamo`oalewa (red).](https://image.slidesharecdn.com/aegispresentation2-250527083700-537c2a13/85/ACT-Science-coffee-presentation-about-asteroid-collision-probability-computation-21-320.jpg)
ACT Science coffee presentation about asteroid collision probability computation
- 1. 1 ESA UNCLASSIFIED – For ESA Official Use Only Monitoring impacts of asteroids: the Aegis system of the ESA NEO Coordination Centre Marco Fenucci, Laura Faggioli, Francesco Gianotto, et al. ESA NEO Coordination Centre ESA Advanced Concepts Team Science Coffee 23/05/2025
- 2. 2 The Three Pillars Of ESA Planetary Defence Detect Assess Mitigate Provide Information
- 3. 3 The ESA NEO Coordination Centre The NEO Coordination Centre (NEOCC) is the operational centre of the ESA Planetary Defence Office (PDO) It is located in ESRIN (Italy) Fig. 1. The main entrance of ESRIN. Fig. 2. Inside the NEOCC office.
- 4. 4 The Risk Assessment Pillar Main activities of the Risk Assessment Pillar Fig. 3. Mr. Squak, the risk assessment pillar mascotte. Asteroid orbit determination Impact probabilities in the next 100 years Detection and analysis of imminent impactors
- 5. 5 The Aegis software Aegis [1] Asteroids Orbit Determination and Impact Monitoring In Greek mythology Aegis is the shield used by Zeus. The Aegis was said to be imbued with divine power and was depicted as a shield adorned with the head of a Gorgon, Medusa. [1] Fenucci et al. (2024). The Aegis orbit determination and impact monitoring system and services of the ESA NEOCC web portal, CMDA 136:58 Development Operations Evolution
- 6. 6 Orbit Determination Observations: ri i = 1, ..., m Prediction function: Residuals: Target function: Dynamical model: Gravitational attractions General Relativity Earth and Sun J2 Non-gravitational effects [2] Milani & Gronchi (2009). Theory of Orbit Determination [3] Veres et al. (2017). Statistical analysis of astrometric errors for the most productive asteroid surveys, Icarus 296 [4] Farnocchia et al. (2015). Star catalog position and proper motion corrections in asteroid astrometry, Icarus 245 [5] Carpino et al. (2003). Error statistics of asteroid optical astrometric observations, Icarus 166 Fig. 4. Massive main belt asteroids included in the dynamical model.
- 7. 7 The NEOCC Orbital Catalogue MPC • MPECs • Daily Update • Monthly OD • From scratch • Update orbit Catalogues • Add new NEOs • Update orbits
- 8. 8 The NEOCC Orbital Catalogue Fig. 5. Orbital elements comparison with JPL orbits, numbered NEOs. Fig. 6. Orbital elements comparison with JPL orbits, unnumbered NEOs.
- 9. 9 Impact Monitoring Summary of the algorithm [6]: Line of Variations (LOV) sampling of the uncertainty region LOV propagation for 100 years Analysis of returns on the Target Plane (TP) Virtual Impactors (VI) search Impact probability (IP) computation Completeness limit: IP ~ 10-7 Fig. 7. Schematic representation of the target plane [7]. [6] Milani et al. (2005). Nonlinear impact monitoring: line of variation searches for impactors, Icarus 173 [7] Farnocchia el al. (2019). Planetary encounter analysis on the B-plane: a comprehensive formulation, CMDA 131
- 10. 10 The NEOCC Risk List Information on: • Impact probabilities in the next 100 years • Palermo and Torino Scales • Details about impact conditions • Historical data • Results are publicly available The NEOCC Risk List is independent from • NASA Sentry Risk List • NEODyS Risk Page
- 11. 11 The NEOCC Risk List
- 12. 12 The NEOCC Web Portal Data available at https://neo.ssa.esa.int Services supported by Aegis: • Risk List • Close Approaches • Orbital Information • ESA NEO Toolkit • Orbit Visualizers • Fly-by Visualizer • Ephemerides service (HTTPS APIs)
- 13. 13 The NEOCC Web Portal – Example data Example 1. Orbital data of 2024 YR4. Example 2. Close approaches of 2024 YR4. Example 3. Earth MOID of 2024 YR4.
- 14. 14 A practical Planetary Defence Scenario: 2024 YR4 Asteroid 2024 YR4 in summary: Discovered on 27/12/2024 by ATLAS Chile Estimated diameter: 60 ± 7 meters Close approach on 22/12/2032 IP at discovery: 5 x 10-4 Close approach uncertainty at discovery: ~1400 ER Torino Scale at discovery: 1 End of observation windows for: 2 m class telescopes: ~10 Feb. 2025 4 m class telescopes: ~4 Mar. 2025 10 m class telescopes: ~1 Apr. 2025 JWST: ~3 May 2025 Fig. 8. Heliocentric orbit of 2024 YR4.
- 15. 15 A practical Planetary Defence Scenario: 2024 YR4 Evolution of risk assessment of 2024 YR4: Continuos follow-up and precoveries efforts IP continued to grow in the first half of Jan. 2025 Reached 1% on 27 Jan. 2025 Torino Scale hit 3 Coordination with NASA JPL and NEODyS Notification by IAWN on 29 Jan. 2025 IP reached highest ever value of 2.8% on 18 Feb. 2025 IP suddenly drops towards 0 in the week after IP with the Moon currently at ~3% Next observation window: from Aug. 2028 Fig. 9. IP evolution of 2024 YR4 with the computation date. TS=3 IAWN Notification IP = 2.8% Higest ever
- 16. 16 A practical Planetary Defence Scenario: 2024 YR4
- 17. 17 There is much more than operations...
- 18. 18 Recent research work supported by Aegis Automated Yarkovsky effect detection [8] • da/dt predicted by physical model • da/dt computed by orbit determination • Outlier identification: • Statistical test with prediction • Dependency on isolated tracklets • 368 positive detections • Data on NEOCC portal [8] Fenucci et al. (2024). An automated procedure for the detection of the Yarkovsky effect and results from the ESA NEO Coordination Centre, A&A 682, A29 Fig. 10. Distribution of Yarkovsky effect detections as a function of the diameter [X], with outliers.
- 19. 19 Recent research work supported by Aegis [9] Fenucci et al. (2025). Astrometry, orbit determination, and thermal inertia of the Tianwen-2 target asteroid (469219) Kamo`oalewa, A&A [10] Novaković and Fenucci (2024). ASTERIA – Asteroid thermal inertia analyzer, Icarus 421 Kamo`oalewa, target of the Tianwen-2 mission [9] • New observations from Loiano and Calar Alto (2024) • Yarkovsky effect detection with SNR ~ 14 • Estimation of thermal inertia through ASTERIA [10] • Regolith grain size extrapolation Fig. 11. Conductivity (left) and thermal inertia (right) distribution of Kamo`oalewa obtained with ASTERIA. Loiano
- 20. 20 Recent research work supported by Aegis Ab initio strewn fields [11] • Entry point at 100 km altitude • Single fragmentation model through atmosphere • Drag force and wind modeling • Reproduced cases of 2008 TC3, 2023 CX1 and 2024 BX1 The fall of 2024 XA1 [12] • Impact predicted by ESA Meerkat [13] • Impact point uncertainties at 100 km altitude • Almost-live and final ab initio strewn field [11] Carbognani et al. (2025). Ab initio strewn field for small asteroid impacts, Icarus 425 [12] Gianotto et al. (2025). The fall of asteroid 2024 XA and the location of possible meteorites, Icarus 433 [13] Gianotto et al. (2024). Meerkat asteroid guard–ESA’s imminent impactor warning service, 2nd NEO and Debris Detection Conference Fig. 12. Entry of 2024 XA1 (top) into the atmosphere and predicted strewn field (bottom).
- 21. 21 Recent research work supported by Aegis [14] Cano et al. (2025). Asteroid detection polar equation calculation and graphical representation, A&A 693, A183 Detection polar equation [14] • Level surfaces for visual magnitude • Helps in analyzing observability • Nice visualization in the NEO Toolkit Synodic Orbit Visualization Tool (SOVT) • Catalogued and custom objects Fig. 13. Detection polar (yellow) and orbit of Kamo`oalewa (red).
- 22. 22 Monitoring Imminent Impactors Service for monitoring imminent impactors: • Tailored for unconfirmed objects • Earth impacts search in the next 30 days • Early alerts to follow-up astronomers Asteroids identified before impact: 7 Fig. 14. Predicted impact location of 2023 CX1. Fig. 15. Atmospheric entry of 2023 CX1 (Credits: Gijs de Reijke).
- 23. 23 Thank you!