Chennai: Indian Space Research Organisation (ISRO) is all set to launch Chandrayaan-1, the country’s first unmanned moon mission, with the beginning of 49-hour countdown early today.

“The countdown for the launch of Chandrayaan-1, which began this morning at 5:22am is progressing smoothly, SDSC associate director Dr M Y S Prasad told PTI.

The Chandrayaan-1 sits on the second launch pad of Satish Dhawan space centre at Sriharikota, about 100km north of Chennai, 11 October. Reuters

All operations were progressing satisfactorily for the launch of the spacecraft. “The 49-hour countdown has number of activities including the major propellant filling of PS-2 and PS-4," he said.

Earlier the countdown was set to 52 hours. “Since all the formal activities for the launch was finished three hours earlier from the original schedule, the countdown time was set at exactly 5:22am today, Prasad said.

“About 43 tonnes of propellant would be filled during the countdown period. Pressurisation of actuators (mechanisms) will also be done at the same time," he added.

Prasad said it would take about 32 hours for both filling of propellants and pressurisation. Other things, including couple of launch testing will also be done during the period.

He said after the rehearsals, SDSC officials had ensured that everything was in place before the countdown. “All the preparatory works, including the checking of 11 payloads, were done successfully before the countdown," he said.

The officials were optimistic that weather would not interrupt the launch of Chandrayaan-I. “Rain does not matter for us as the spacecraft is fully rain proof. Even if it is drenched with water there is no problem. The launch would take place as per schedule," Prasad said.

However, he said if it was a cyclone threat, there was a possibility of rescheduling the launching time.

According to the statistics given by the SDSC officials, Chandrayaan-I spacecraft carrying 11 payloads (scientific instruments) weighs about 1,380kg at the time of its launch and was shaped like a cuboid with a solar panel projecting from one of its sides.

The eleven payloads, five entirely designed and developed in India, three from European Space Agency, one from Bulgaria and two from US, would expand various scientific knowledge about the moon, he said.

The spacecraft was powered by a single solar panel generating maximum of 700 W. A 36 Ampere-Hour (AH) Lithium ion battery supplies power when the solar panel was not illuminated by the Sun.

To make the spacecraft escape from orbiting the earth and to travel towards moon, its Liquid Apogee Motor (LAM) was used. Officials said the journey to Moon would take five and half days. In its two-year life, the satellite would also search for water in the Moon.

Explaining about the ground segment, the officials said the ground facilities of Chandrayaan-I perform the highly important task of receiving the microwave containing the health information of the spacecraft as well as the valuable scientific information, which the spacecraft sends. It also transmits the radio commands to be sent to the spacecraft during all the phases of its mission.