HYDERABAD, India - China plans to land a 1,300-kilogram (2,900-pound) lander on the moon in 2015-17 that also would serve as a testbed for a sample-return lander to follow by 2020, one of the China National Space Administration engineers working on the project said here Sept. 28.

The Chinese government already has approved both missions as follow-ons to Chang'e-1, set for launch before the end of this year, according to Peng Jing of the China Academy of Space Technology. Work on the lander, which will carry robotic arms and a rover for geology and other science, already has started, Peng told a lunar-exploration symposium at the 2007 International Astronautical Congress.

A full-scale drop test to simulate the final few meters of the lander's descent caused structural damage to the lander test article - a four-legged configuration not unlike the Apollo-program Lunar Excursion Module in its undercarriage design. Peng said the mishap apparently was the result of a flaw in that design, coupled with excess weight in the test rig.

The lander's flight-profile calls for a 4-meter (13-foot) free fall at the end to avoid contamination of the site and dust on its camera lenses. Peng said the current plan is to use a 5-1 throttleable engine for a powered descent from about 15 kilometers (9 miles) altitude, with an autonomous landing guided by altitude and speed sensors and a terrain-imaging system able to shift the lander horizontally to an alternate site if obstacles are detected at the primary.

Weighing 4,000 kilograms (9,000 pounds) at launch while still loaded with propellant, the lander would use a Long March CZ-3B launcher to go directly into lunar transfer orbit. It would orbit the moon several times at an altitude of 100 kilometers (60 miles), the same orbit as is planned for Chang'e-1, before beginning its descent.

After the planned unpowered drop to the surface, the final impact would be cushioned by crushable honeycomb material or a hydraulic system in the four landing struts, Peng said.

For its nominal 90 days of surface operations the lander would shift from solar power to a Pu-238 Radioisotope Thermo-electric Generator (RTG) that China will either develop or buy abroad, probably from Russia.

Although it won't have an ascent stage, Peng said that the rover, robotic arms and perhaps a drill would be precursors to those that would be used to collect samples on the mission to follow. The rover would be mounted on top of the lander until touchdown, and then would drive onto a ramp unfolded to the horizontal and lowered to the surface, according to drawings presented with the technical paper submitted by Peng and his colleagues.

The lander is larger than necessary for the first mission, Peng said, but is being designed to generate heritage for the sample return mission to follow.