NASA is studying a plan for astronauts above the far side of the moon to control a rover on the surface. But justifying such a mission won't be easy.

The demise of the space shuttle has forced NASA to scale back its human activities in space. Without its own vehicles for launching astronauts into space, there is little the organisation can do but dream of better times ahead.

Its current plan is to build a vehicle called Orion that will have the capability to support a small crew for up to 21 days, long enough to get to the moon and back. NASA is also greedily eyeing other potential destinations, such as near Earth asteroids.

Today, Jack Burns at NASA's Lunar Science Institute in Moffet Field, California, and a few buddies have come up with another suggestion. These guys say that a moon landing is a risky goal so why not try an easier, intermediate mission first.

Their idea is to send an Orion spacecraft on a lunar fly-by past the moon to the L2 Lagrange point some 65,000 kilometres beyond. This is the place where gravitational forces exactly balance the spacecraft's centripetal force, allowing it to seemingly hover above the moon (although in reality it will orbit the L2 point).

The advantage, say Burns and co, is that from L2, the astronauts will be able to see both Earth and the far side of the moon at the same time.

From here, the astronauts will operate a remote-controlled rover on the far side of the moon that will be sent ahead of the crewed mission.

Remote control from L2 will be much better than from Earth, say Burns and co. That's because the round-trip communication time between the rover and L2 is only 0.4 seconds, compared to the almost 3-second round-trip time to Earth.

Experiments on Earth suggest that an 0.5 second delay is the maximum "cognitive horizon" that humans can cope with and still achieve a telerobotic presence.

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Astronauts Could Remotely Control Moon Rovers from Lunar Orbit, Says NASA Plan