Lost in Space? Not With Lunar GPS

July 23, 2008 -- One challenge with sending astronauts to unexplored regions of the moon is making sure they don't get lost.

The sojourners of the Apollo era had it easy, compared to what NASA plans for when astronauts return to the moon beginning in 2020.

The next generation of lunar explorers is expected to venture into regions that have limited radio contact with Earth.

"The proposed mission sites at the lunar south pole don't have the visibility to Earth that the Apollo landing sites had," said Bryan Welch with NASA's Glenn Research Center in Cleveland, Ohio. "Low elevation levels cause very poor visibility and if you happen to be in a crater, there may be no visibility."

To prevent astronauts from becoming disoriented, NASA is developing a navigation system so moonwalkers can orient themselves on their own, similar to how signals from the Global Positioning System network are used on Earth.

Getting lost on the moon could be fatal. Astronauts' spacesuits have limited supplies of air and other life-support equipment and the lunar landscape doesn't offer many visual cues for wayward travelers.

Rather than a pricey string of satellites -- there are about 30 operational spacecraft in the GPS network today -- the moon system will rely on signals sent from lunar beacons, stereo cameras and sensors on orbiting spacecraft.