The weather conditions over the Sriharikota spaceport were being closely monitored and officials said there is no chance of the launch being postponed unless a cylonic threat emerged, as the polar rocket that will put the spacecraft into lunar orbit was being fuelled.

"Everything is going in order. We are ready to launch on the dot," a space official said, as hundreds of scientists went through the 49-hour countdown drill with precision.

The 1,380 kg spacecraft would be put into orbit by India's home-grown rocket PSLV-C11 which is due to blast off at at 6.20 am on Wednesday from the second launch pad at Satish Dhawan Space Centre Associate Director(SDSC).

The work on filling of propellant for the first stage of the polar launch vehicle had been completed and the second stage filling would be over on Tuesday night, SDSC Associate Director Dr M Y S Prasad told PTI.

"The countdown, which started at 5.22 am yesterday, is progressing smoothly and the propellant filling of PS-2 (first stage) has been completed," he said adding a total of about 43 tonnes of propellant would be filled.

Asked about weather conditions in this space port town, which is witnessing isolated rains, Prasad said the rains would not affect the launch. "The rain does not matter as the spacecraft is fully rain proof. Even if it is drenched, the launch would take place as per schedule."

However, the launch might have to be rescheduled if there was cyclonic weather conditions, he added.

Elite status

Chandrayaan-1 would put India in the elite lunar club comprising Russia, US, Japan, China and European Space Agency, who had undertaken unmanned exploratory missions to the moon.

The mission intends to put an unmanned spacecraft into an orbit around the moon and to perform remote sensing of the nearest cleestial neighbour for about two years with eleven payloads (scientific instruments).

It would reach the moon surface in the second week of November RPT in the second week of November. Later, the moon impact probe would be ejected from Chandrayaan-1 over RPT over the moon surface in a chosen area.

Following this, cameras and other scientific instruments were turned on and throughly tested. This leades to the operational phase of the mission.

This phase lasts about two years during which Chandrayaan-1 would explore the lunar surface with its array of instruments that includes cameras and spectrometers.

The solar-powered Chandrayaan-I, carrying 11 payloads, weighs about 1,380 kg at the time of its launch and was shaped like a cuboid with the solar panel projecting from one of its sides.

Of the the eleven payloads, five are entirely designed and developed in India, three from European Space Agency, one from Bulgaria and two from the US.

Chandrayaan-1 aims to achieve scientific knowledge through high-resolution remote sensing of moon in the visible, near infrared, microwave and x-ray regions of electromagnetic spectrum.

With this, preparation of a three-dimensional atlas of the lunar surface and chemical and mineralogical mapping of entire moon surface was invisaged.