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Wednesday, July 7, 2004 Mars GPS Planned Mars. Credit: NASA/JPL How do you tell a rover millions of miles away to go look at a rock? Unfortunately, even if you figure out the right sequence of commands, the best you can do is send the commands, and hope. And then you figure out where the rover is. Maybe there was a rock in the way that threw the rover off track, or maybe the wheels slipped a little bit. Maybe it fell down a crater. Modern rovers have complicated devices for figuring out where they are. Inertial guidance systems are combined with advanced imaging software that uses landmarks are employed by Spirit and Opportunity. When the orbiters are in the right position, they can even try using Doppler shift. But even with all that, simply finding out where they are after moving takes an inordinate amount of time that could be better spent on discovering clues to Mars' geology and past. That's all going to change. As the number of orbiters around Mars grows, they are increasingly being used as communications relays and positioning satellites. The 2009 Mars Telecommunications Orbiter will combine the existing and future Mars satellites into a GPS system that will grow over time. While original plans called for a Marsnet of tiny satellites to serve this role, NASA has determined that they can create a GPS system equivalent to the degraded Earth GPS from before the military allowed commercial access -- that is, 10 to 100 meters resolution. Not only will the new network be a vital asset to future robotic missions, it will also be able to do science of its own, by probing the ionosphere through its radio emissions. Perhaps more importantly for the future, it may also serve as a vital tool in the future human exploration and colonization of the planet. (More info: Yahoo! News) @ 23:21 EST