  Dragonfly is scheduled to begin exploring Titan by 2034 using a series of
multi-kilometer surface flights. This paper outlines the preliminary design of
the navigation filter for the Dragonfly Mobility subsystem. The software
architecture and filter formulation for lidar, visual odometry, pressure
sensors, and redundant IMUs are described in detail. Special discussion is
given to developments to achieve multi-kilometer surface flights, including
optimizing sequential image baselines, modeling correlating image processing
errors, and an efficient approximation to the Simultaneous Localization and
Mapping (SLAM) problem.
