The 49-hour countdown for the launch of India's maiden unmanned moon mission scheduled to blast off on Wednesday from Sriharikota is progressing smoothly and there is no chance of the launch being postponed unless a cyclonic threat emerged, officials said.

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 tonight, Satish Dhawan Space Centre Associate Director Dr M Y S Prasad told PTI in Sriharikota (AP), 80 km north of Chennai.

"The countdown, which started at 5.22 am on Monday, 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, he 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," he said.

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

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