gracefully recover from errors, handle ambiguities, and integrate sensor data in a consistent way. Moreover, a probabilistic robot knows about its own ignorance—a key prerequisite of truly autonomous robots.
These sterling qualities sound like a working definition of mature human wisdom, and could provide a superior basis for a high level of robotic intelligence.
Despite these and other advances, no artificial being so far dis- plays general visual comprehension at the human level, but artificial vision works well within certain categories essential for beings that are mobile or meant to interact with people.
FROM HERE TO THERE
To move from one location to another, an artificial being must know its starting position, plan a route, and make the journey without hit- ting anyone or anything—hence localization, mapping, and obstacle avoidance form a basic set of visual abilities. Using these abilities, more or less autonomous mobile digital beings are becoming almost common sights in a variety of arenas—the home, hospitals, museums, the battlefield, and on distant planets as part of NASA’s exploration of space.
NASA cannot yet send astronauts to other planets, so the agency has pioneered in developing mobile robotic stand-ins for human ex- plorers.The Robonaut unit described earlier is not one of these stand- ins, because the focus is on moving its arm and hand rather than its whole body, and its visual cognition comes from a human operator. But the Sojourner rover, a small, wheeled unit delivered to Mars by the Pathfinder mission and that began examining Martian rocks on July 4, 1997, was the first in a series of mobile exploration robots with visual abilities.
The latest NASA mission to Mars began with two spacecraft launched in June and July, 2003, each carrying a new rover. In January 2004, the spacecraft delivered these nearly identical robots—dubbed Spirit and Opportunity—to two widely separated areas of the planet, carefully chosen because they show signs that liquid water might have flowed there in the ancient past. If the robots determine that liquid