Aegis: ESA's Planetary Defence Office orbit determination and impact monitoring software

The aim of impact monitoring is to determine whether a near-Earth object (NEO) could possibly impact the Earth or not. It is essential to perform this activity as soon as new observations of NEOs are released, in order to improve the orbit of possibly impacting asteroids by a quick follow-up campaign.

Here we introduce Aegis, an automated orbit determination and impact monitoring system, developed by SpaceDyS s.r.l. and operated by ESA's NEO Coordination Centre (NEOCC). Our new system is completely independent from the Sentry and Clomon-2 systems, operated by NASA and NEODyS, respectively. The Aegis system updates astrometric data of asteroids from the Minor Planet Center on a daily basis, and provides a catalogue of NEOs which comprises orbits with their uncertainties, some physical properties, observations and residuals, close approaches and ephemerides.

More importantly, it computes the impact probabilities of NEOs in the next 100 years. All the objects with a non-zero impact probability are collected in the so-called Risk List, displayed in the NEOCC web-portal. When the impact probability is high enough, the software is able to compute the related impact corridor.

All the data generated are publicly available in the NEOCC web-portal and used also as input of several tools and services, such as the orbit and flyby visualisers, ephemerides requests and all the tools of the NEO Toolkit.