New Delhi - India's first-ever moon mission, due for launch Wednesday, was expected to return a rich yield of scientific information on Earth's neighbour besides being a template for international participation in space expeditions.

A 49-hour countdown for the launch of Chandrayaan-1, which means mooncraft in Sanskrit, began Monday at the Satish Dhawan Space Centre on Sriharikota Island, 90 kilometres north of Chennai.

The 1,380-kilogramme spacecraft - built by India's national space agency, the Indian Space Research Organization - is to be carried into lunar orbit by a four-stage rocket with six strap-on propellants weighing 12 tons each.

The Chandrayaan is to take about five days to reach the moon and would be placed in a 100-kilometre polar orbit, from where it is to study the moon for two years.

Should the mission to unravel the moon's mysteries be successful, it would catapult India into the club of space-faring countries, which includes the United States, Russia, Europe, China and Japan.

Scientists said that despite more than 65 manned and unmanned missions to the moon over the past half-century, not everything about the moon was understood.

The theory that the moon originated after a catastrophic collision of the Earth with a Mars-sized body more than 3 billion years ago was still unproven, they said.

"The mission will fill gaps in the knowledge of the moon and will provide extensive information on aspects of the moon's structure, geological history, its origin and in turn to throw light on the origin of Earth itself," said G Madhavan Nair, chairman of the Indian space agency.

The Chandrayaan is to conduct a range of studies, some of which have not been attempted before, including high-resolution sensing of the moon, preparing a three-dimensional atlas of its near and far sides, chemical and mineralogical mapping as well as searching for the presence of water in its polar regions.

Indian scientists said the mission is different from other lunar missions because it would generate the highest scientific returns.

"Chandrayaan is a purely Indian mission, but it is the first time there is international participation on such a scale on a moon mission from one country," S Satish, the space agency's director, said by telephone. "There are 11 payloads, probably, the most carried by a spacecraft to the moon."

The payloads include five designed by the Indian space agency; three devised and contributed by Germany, Britain and Sweden from the European Space Agency; two from the US space agency; and one from the Bulgarian Academy of Sciences.

Satish said the project cost was estimated at 3.9 billion rupees (80 million dollars) and was up to one-fifth the cost of similar expeditions because most of the equipment was built in India.

"It is not only the cheapest-ever lunar expedition but is likely to return the maximum scientific data and value for the costs involved," he said.

India's moon mission comes at time when there is a renewed interest in the moon as the world's space powers have started planning missions to study its resources and use it as a base for space exploration.

China and Japan launched moon missions last year while NASA's Lunar Reconnaissance Orbiter is due for an April 2009 launch. All these missions are to orbit the moon to carry out studies.

Satish said India's mission would also be significant because it would investigate the presence of helium-3, believed to be abundant on the moon and sought for nuclear fusion research and energy generation.

India's tryst with space began with the formation of its space agency in 1962. Thirteen years later, India launched its first space satellite, Aryabhatta. In 1984, India sent Rakesh Sharma as its first cosmonaut to the Soviet space station Salyut-7.

In recent years, India concentrated much of its space development on sophisticated satellites, aiming to capture a part of the global commercial satellite launch market.

Scientists said they expect Chandrayaan-1 would be a stepping stone for the 2011 unmanned Chandrayaan-2 mission, a collaboration between Indian's and Russia's space agencies, which would include a lander and a rover. That mission could be followed by the country's first manned mission to the moon by 2015.

"Indian scientists say Chandrayaan could be a small step for space missions but a giant leap for India's space programme," said Kalyan Ray, a science writer with the Bangalore-based Deccan Herald. (dpa)