Asteroids are primordial remnants from the early Solar System, offering invaluable insights into planetary formation and the origins of organic compounds that may have played a role in the emergence of life on Earth. Understanding their composition, structure, history and evolution is pivotal for addressing fundamental questions in planetary science and astrobiology. Furthermore, near-Earth asteroids (NEAs) pose both scientific opportunities and potential hazards, making their study critical for planetary defence and resource utilization. The Italian Space Agency (ASI) has planned initiatives to define mission concepts for asteroid robotic exploration. These would enable new technological developments and, at same time, consolidate the national heritage built over the past decades through the realization of asteroid monitoring systems and contribution to interplanetary missions with international partners.
The AEGIS (Asteroid Exploration mission for Geophysical Investigation and in-Situ analysis) mission concept  aims at demonstrating technological capabilities to rendezvous with an asteroid, precisely land on its surface, as well as performing detailed in situ-analysis. In particular, the mission will target a rubble-pile NEA with the possibility to execute one or multiple fly-bys of other NEAs during the interplanetary transfer phase. The mission is composed of an orbiter, which will perform observation and characterization of the asteroid, and a lander which will attempt anchoring, sample retrieval as well as in situ analysis. In addition to its ambitious technological objectives, AEGIS will provide significant scientific insights to answer fundamental questions on the formation of asteroids, their composition, structure, and mechanical properties. Such information has huge implications to assess NEAs potential for in-situ resource utilization (ISRUs) and to devise future planetary defence strategies.
The Phase A study, funded by ASI, kicked-off in November 2024 and concluded 12 months later. The study was conducted by the consortium AENEAS composed of Nautilus – Navigation in Space, Tyvak International, Officina Stellare and DTM with the support of a Scientific team which includes INAF - Astronomical Observatory of Padova, Politecnico di Milano and Università Degli Studi di Bologna. The mission is planned for a launch opportunity in the early 2030s, with an estimated mission duration of approximately 4 years including the interplanetary cruise and asteroid operations phases.
This contribution will focus on the mission analysis and navigation aspects of the AEGIS mission concept. After an overview of the mission objectives, space segment definition including instruments and payload packages for in-orbit prospecting and characterization and in-situ analysis, the target selection process is introduced. In particular, this was a key element in the mission design phase, as the asteroid selection was one of the first task of the study. The selection of the primary and backup targets is based on a reachability analysis performed on a large set of candidate objects, obtained from filtering the NEA dataset according to their orbital and physical characteristics, as well as ISRU compatibility. Low-thrust porkchop plots are generated for each prefiltered asteroid, considering a realistic electric-thruster model with variable specific impulse and thrust that depends on the available onboard power. Feasible launch windows are then identified by considering the available fuel mass, as well as thermal and communication constraints. The innovative method employs convex optimization, allowing fast screening and identification of targets which are compliant with propulsion system and communication limitations. Upon asteroid selection, a refined optimization of the interplanetary transfer is presented, which includes fly-by opportunities of additional NEAs. The asteroid rendezvous and close proximity phases are then introduced, providing details on the orbit selection to fulfil the characterization objectives. The landing approach and trajectory optimization is introduced, including an assessment of the limitations and constraints related to the body’s low gravity and miniaturized spacecraft platform. Finally, navigation analysis performances in the different mission phases are introduced before the concluding remarks.