India's maiden lunar mission, the Chandrayaan-1 spacecraft that launches Oct 22, between 06.15 a.m. and 06.35 a.m.(which is the most optimal time for lift-off, as moon is inclined 28 degrees towards earth at the equator) will orbit about 100 km from the lunar surface for two years, performing remote sensing of the dark side or hidden portion of the moon to unravel its mysteries, scientists working on the project said. Chandrayaan-I would be launched just like any other satellite using the Polar Satellite Launch Vehicle (PSLV). But while other ISRO satellite launches, such as INSAT and IRS, targeted the earth's orbit and went a maximum distance of 36,000 km, Chandrayaan will travel nearly 10 times further, since the moon is 3,86,000 km from the earth. Scientists of the Indian Space Research Organisation (ISRO) are striving to integrate the 1,380-kg spacecraft with the 316-tonne rocket, fitted with six strap-on motors for the D-Day. The 45-metre tall, updated version PSLV is the trusted workhorse launch vehicle of the Indian space agency, with a record of 12 consecutive launches since 1994. The four-stage rocket is equipped with solid and liquid propellants that will fire the strap-on boosters to catapult Chandrayaan into the lunar orbit 18 days after the lift-off, on Nov 8. As India's first spacecraft mission beyond earth orbit, Chandrayaan is aimed at expanding our knowledge about earth's only natural satellite - moon. Orbiting about 100 km from the lunar surface, the spacecraft will perform remote sensing of moon for about two years using 11 scientific payloads, including five instruments designed and developed indigenously. "Moon is the nearest celestial body to earth at a distance of 384,000 km. Formation and evolution of moon are central to understanding the solar system. Though there have been many manned and unmanned lunar explorations, Chandrayaan will be the first spacecraft to explore the dark side or hidden portion of moon and unravel the mystery behind," SDSC deputy director M.S.N. Prasad says.With Chandrayaan, India will join the elite space club comprising the US, Russia, European Space Agency, China and Japan by demonstrating its capability to explore moon with its own spacecraft and launch vehicle. Shaped like a cuboid, Chandrayaan is powered by a single solar panel generating about 700 watts. A 36 ampere-hour (AH) lithium ion battery supplies power when the solar panel, projecting from one of its sides, is not illuminated by sun. The spacecraft's dual gimballed antenna will transmit the precious scientific data collected by its instruments to earth. Within 25 seconds of the lift-off from the second launch pad, the two strap-on motors will fire the rocket to place Chandrayaan into a highly elliptical transfer orbit around earth in the next 110 seconds. After circling earth in its transfer orbit for a while, the spacecraft will be put into more elliptical orbits by repeatedly firing its liquid apogee motor (LAM) at opportune moments.

The LAM onboard will be fired again to make the spacecraft travel to the vicinity of moon by following a path called lunar transfer trajectory (LTT), whose apogee - farthest point from earth - is at 387,000 km. After a detailed observation of the lunar orbit perturbations, the orbital height of Chandrayaan will be finally lowered to its intended 100 km height from the lunar surface. Over its two year period, the mission will survey the lunar surface to produce a complete map of its chemical characteristics and topography. ISRO is likely to launch the spacecraft by October or December this year. "The prime objective of the lunar mission is to expand scientific knowledge about the moon, to upgrade India's technological capability and to provide opportunities for planetary research to Indian scientists," ISRO director S. Satish said.