By Paul Rincon
BBC News science reporter
A US firm is proposing to use guided missile technology to make a precision, automated landing on the Moon.
Missile technology could help craft land on the Moon more precisely
Raytheon has outlined plans for a low-cost lunar lander that uses elements from missiles designed to intercept and destroy enemy warheads fired at the US.
It could be used for missions within President Bush's Moon-to-Mars vision for space exploration.
Engineers explained the proposal at this year's American Geophysical Union Fall Meeting in San Francisco, US.
On its journey to the Moon, the lander would be attached to a cruise stage which handles navigation and other tasks.
The vehicle would use a re-plumbed version of the propulsion system used by Raytheon's "kill vehicle" missiles.
About two minutes before impact on the Moon, a solid rocket booster would reduce the vehicle's speed to 300-450 m/s. The lander itself activates about a minute before impact.
This mimics the operational timeline used for missiles over decades.
The lander is guided to precise coordinates by a Digital Scene Matching Area Correlator (DSMAC). This acquires high-resolution images which are compared with a reference map of the landing site in real time.
Data from the images and from the vehicle's altimeter are then processed to help guide the vehicle to its target. The images taken on the way down can also be used to help scientists study the landing site's geology.
"[Nasa's] navigation requirements, specifically where they wanted to land on the lunar surface, became much more precise," Raytheon vice-president for advanced missile defense, Michael Booen, told the BBC News website.
"So we said we've got a pretty precise navigation capability to put our precision munitions in exactly the right coordinates."
The kill vehicles are a key component of the Pentagon's planned multi-billion dollar shield against warheads fired at the US.
The kill vehicle is designed to intercept enemy ballistic missiles (Image: Raytheon Missile Systems)
They are designed to destroy incoming long-range ballistic missiles during the "midcourse" of their flight - before they re-enter Earth's atmosphere.
However, the so-called ground-based midcourse defense (GMD) system suffered a setback on Wednesday with the failure of its first full flight test in two years. The interceptor missile shut down automatically in its silo due to an "unknown anomaly".
The proposed Moon lander is more suitable for relatively small, unmanned science missions to the lunar surface.
Earlier this year, Nasa awarded Raytheon a contract of almost $1m (£512,000) to be part of a three-company team studying challenges involved in returning to the Moon, as a first step toward human exploration of Mars and other planets.
The "concept exploration and refinement" work was awarded under Project Constellation, the long-term effort to boost human space exploration.