NASA's Top 5 Technical Challenges Countdown: #4: Improved Navigation
But in space, like on the Moon or Mars, we have…none of that. Zero. No GPS satellites, no globe-spanning networks. Just radio broadcasts from command centers here on Earth to tell our robots and crews what to do.

But in space, like on the Moon or Mars, we have…none of that. Zero. No GPS satellites, no globe-spanning networks. Just radio broadcasts from command centers here on Earth to tell our robots and crews what to do.