The design of a low-cost impactor SC, targeting a small, faint NEO, poses major challenges. One of the most demanding problems refers to the capability of the autonomous GNC to compensate the deviations affecting the impact point in order to achieve a successful collision. During the terminal phase, the autonomous GNC must use the information of the optical sensors to estimate the parameters allowing the computation of divert maneuvers to achieve the impact. GMV has developed a simulator, with different levels of sophistication, and a set of different GNC algorithms to help in the design process allowing for dimensioning the sensors and actuators, verifying mission requirements, computing figures of merit of different SC configuration and evaluating GNC performances. The implemented GNC algorithms are (1) low-thrust proportional navigation using a fading memory filter, (2) high-thrust predictive guidance using a Kalman filter or (3) a batch-sequential least-squares filter, and (4) a mid-thrust hybrid predictive-proportional guidance using a fading memory filter. Results of single-run and Monte Carlo simulations for two different asteroids (1989 ML and 2002 AT4) with these GNC algorithms are presented to compare performances and to show the mission parameters driving these performances.
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