Until this upgrade, Perseverance depended on a combination of inertial measurements and visual odometry to track its movements, with operators on Earth periodically correcting its position based on orbital imagery. Over long drives, tiny errors accumulated so that the rover could be off by more than 35 meters, forcing it to halt early when it judged that it might be too close to hazardous terrain and wait for updated instructions. With Mars Global Localization, the rover can now stop, autonomously match a newly acquired 360 degree panorama to maps from Mars Reconnaissance Orbiter, and then continue along a preplanned route without waiting for human confirmation.

Mission engineers describe the new capability as the rough equivalent of providing the rover with GPS on a planet that has no satellite navigation network. Vandi Verma, chief engineer of robotics operations at NASA's Jet Propulsion Laboratory, said the system means Perseverance can drive much longer distances autonomously, allowing the mission to explore more terrain and gather more science while reducing demands on the ground team. The technology is designed to be adaptable to other rovers that need to travel quickly and over large distances on Mars or other worlds.

Mars Global Localization builds on Perseverance's AutoNav self-driving system, which already enables the rover to re-plan routes around obstacles on the way to a designated destination. In practice, AutoNav's performance has been limited less by onboard path-planning and more by uncertainties in the rover's absolute position. By removing that constraint, the new localization process allows the team to command drives of effectively unlimited length between communication sessions, provided terrain and power considerations allow.

The algorithm's orbital matching requires more computing power than Perseverance's two main radiation-hardened computers can efficiently provide, so engineers turned to the Helicopter Base Station mounted on the rover. That unit, used as a radio relay for the Ingenuity Mars Helicopter, carries a commercial processor similar to those in mid-2010s smartphones and runs more than 100 times faster than the rover's primary avionics. Ingenuity flew 72 times instead of its originally planned five, demonstrating that commercial processors can survive and function effectively in the Martian environment and inspiring engineers to reuse the hardware for surface navigation.

To ensure reliability when using the commercial processor, the team implemented a "sanity check" process in which the localization algorithm runs multiple times on the Helicopter Base Station before one of the main computers verifies the consistency of the results. During development, engineers discovered that a small region of memory equivalent to about 25 bits in the processor's 1 gigabyte had been damaged, causing a consistent 1 millimeter error in the reported position. They responded by isolating those bits from use while the algorithm runs, restoring accurate performance.

The Mars Global Localization system was validated with a campaign that began in 2023, using data from 264 previous rover stops to test its accuracy. For each stop, the algorithm matched rover panoramas to Mars Reconnaissance Orbiter images and successfully recovered the rover's true position. Jeremy Nash, the JPL robotics engineer who led the implementation under Verma's supervision, noted that global localization has been an open problem in robotics for decades and called the deployment of the solution on Mars a first in space exploration.

Mars Global Localization complements another recent software enhancement on Perseverance that applies generative artificial intelligence to drive planning. In that earlier upgrade, an AI system selected waypoints for the rover's route, a task traditionally handled by human planners, similarly intended to increase daily drive distances and reduce the workload on operators. Together, the AI waypoint planning and the new localization capability are intended to help Perseverance cover more ground, more quickly, as it continues its campaign to explore Jezero Crater and collect samples for possible return to Earth.

The team expects that techniques developed for Mars Global Localization, including robust image matching and error checking on commercial processors, will prove useful for future missions. Engineers are already looking toward applications on the Moon, where extreme lighting conditions, long nights, and rugged terrain will make accurate, independent navigation critically important for both robotic and crewed vehicles. As more missions adopt faster commercial-grade computing hardware, the experience gained with Perseverance may guide designs that balance performance with the need for fault detection and mitigation in harsh space environments.

Related Links
Mars Global Localization - PDF Primer
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