Enabling Long Precise Drives for The Perseverance Mars Rover via Onboard Global Localization

The Perseverance Mars rover needs to drive long distances between regions of scientific interest to collect a diverse set of samples. Position knowledge is needed for navigating to the region of interest. Planetary mobile robots accumulate position uncertainty as they move. Globally localizing the robot to an orbital map of Mars removes this uncertainty. To date, this has been performed manually on the ground by humans for mobile surface and aerial robots. This can be accurate but requires communication between planets. This takes significant time and the need for it limits how far Perseverance can autonomously navigate without ground-in-the-loop. This paper describes a new onboard approach for performing global localization, much of which already has been successfully demonstrated on Perseverance. Our Censible technology uses a modified census transform to achieve sub-meter global localization accuracy that is robust and practical, and whose performance matches human-directed localizations from the first two and a half years of the mission to within 0.5 meters on average with no outliers. We use the fast processor on the Ingenuity Helicopter Base Station to perform the localization. This processor was originally mounted in the Perseverance rover to coordinate communication with Ingenuity, and radiation mitigation methods were implemented to enable its use as a rover co-processor as part of this effort. The system is designed to limit operations impact and requires no daily input from rover operators other than whether or not to perform global localization, but also allows strategic configuration options if desired. This paper discusses the lessons learned from developing and deploying this new technology on a flight mission. We describe how global localization is expected to increase science return and change how we navigate planetary mobile robots.