Autonomous image based localisation for a martian aerobot

Balloon based aerobots have much to offer ESA's future planetary exploration programmes, e.g. high resolution mapping, landing site selection, rover guidance, data relay, sample site selection, payload delivery, and atmospheric measurement and meteorology. Aerobots could be used in a variety of configurations from uncontrolled free-flying to tethered rover operation, and are able to perform a range of important tasks which other exploration vehicles cannot. In many ways they provide a missing 'piece' of the exploration 'jigsaw', acting as a bridge between the capabilities of in-situ landers and rovers and non-contact orbiters. Technically, a Lighter than Air (LTA) aerobot concept is attractive because it is low risk, low-cost, efficient, and much less complex than Heavier than Air (HTA) vehicles such as fixed wing gliders, and crucially, much of the required technology 'building blocks' currently exist. Smart imaging and localisation is a key enabling technology for remote aerobots. Given the current lack of comprehensive localisation and communications systems, it is important that aerobots are equipped with the ability to determine their location, with respect to a planet's surface. The availability of a variety of terrain feature extraction, point tracking, and image compression algorithms, means that a self-reliant system is now achievable. We have developed a demonstrator imaging and localisation package (ILP) for a Martian balloon. This ILP system incorporates a unique combination of image based relative and absolute localisation techniques. We have demonstrated our ILP using both simulation and a real laboratory based model aerobot. The availability of both simulated and real aerobot data thus providing a comprehensive test and evaluation framework for the ILP functionality. The results from our work are presented in this paper.