Trey Smith and Dominic Jonak, the 20-something programmers in the 4x4, consider tinkering with Zo´s navigation algorithm so it can better handle the unexpected terrain. Or they could rewrite this part of the Pittsburgh scientists´ plan on their laptops and download it to Zo. But according to the rules of the game, they mustn´t override the science team unless it´s absolutely necessary. If all else fails, there´s always the joystick. "OK, we´re not going to learn anything else," Wettergreen calls out. "Let´s get this thing turned around."
On the bright side, the robot hasn´t done any violence to itself, no end-over-end flips or collisions with intervening large rocks. "That used to be the kind of problem you worked on endlessly," Wettergreen says, "getting the robot not to crash into stuff."
Still, as this incident suggests, Zo´s autonomous navigation is hardly foolproof. The problem is long-range vision: It doesn´t have any. The integration of the pan-tilt camera unit with the navigation system is still on the to-do list. Hence, big-picture decisions-which slope to climb, how best to cross the drainage area-are beyond the ´bot.
"We´re pushing every system in this robot so hard, breakdowns are inevitable," Wettergreen tells me. "I like to have 80 percent of things working. More than that, and we´re not trying enough."
Life Under the SpotLight
Zo´s capacity to drive itself is the fruit of years of robotic-autonomy research. In contrast, its life-sensing system, the camera that descends from the undercarriage on vertical rails to capture fluorescent images, was recently developed by Carnegie Mellon´s imaging guru, Alan Waggoner.
Under the right conditions, organic molecules fluoresce in specific ways that can be captured photographically. In the past two decades, fluorescence microscopy has helped decode the human genome and given us a fast, reliable HIV test. But that sort of technology is done in darkened lab conditions, and Zo, being solar-powered, doesn´t like to work nights. Waggoner´s solution: He outfitted Zo with a high-powered flash that blasts the ground with light, timed to the camera´s 1/50,000-of-a-second exposure. In that moment, the flash imparts enough energy to excite the organic molecule-chlorophyll, say-to fluoresce, while overwhelming any confounding effect that ambient sunlight would otherwise have on the image.