Chandrayaan 2, India's Rs 1,000 crore moon mission, will be launched today (File Photo)

Highlights The 20-hour countdown for the launch began Sunday evening

The countdown is progressing normally, sources in ISRO told NDTV

ISRO chief has called Chandrayaan-2 "most complex mission ever"

India's space scientists have a narrow one-minute window for their second attempt at launching moon mission Chandrayaan 2 today, a week after the mission was aborted 56 minutes before lift-off. Chandrayaan 2 will be launched this afternoon at 2.43 pm from Andhra Pradesh's Sriharikota.

Scientists of the Indian Space Research Organisation (ISRO) offered prayers at temples near the base and said there would be no repeat of last week's problem.

The 20-hour countdown for the launch of the Rs 1,000-crore mission began Sunday evening at 6.43 pm. Similar time slots for launch attempts will be available till July 31, say scientists, after which a window will be available only in September.

In tweets, ISRO said it had completed the fuelling the liquid core stage of the Geosynchronous Satellite Launch Vehicle Mark 3 (GSLV Mk 3) rocket, nicknamed 'Baahubali'.

The countdown is progressing normally, sources in ISRO told NDTV.

The weather looks benign with a slightly cloudy sky. Rockets usually do not get affected by rain but lightning could be an issue. As of now all systems are set for the 2.43 pm lift off, said sources.

The success of Chandrayaan 2 mission will make India the fourth country after the US, Russia and China to pull off a soft landing on the moon.

#ISROMissions

The launch countdown of #GSLVMkIII-M1/#Chandrayaan2 commenced today at 1843 Hrs IST. The launch is scheduled at 1443 Hrs IST on July 22nd.

More updates to follow... pic.twitter.com/WVghixIca6 - ISRO (@isro) July 21, 2019

The mission was stopped 56 minutes and 24 seconds before its launch last Monday after a technical snag was discovered in the unmanned launch vehicle system. ISRO said the decision was taken "as a measure of abundant precaution".

A senior ISRO official had earlier told NDTV that had the problem not been rectified, Chandrayaan 2 would have been a "total failure".

"The problem was serious, but simple to resolve. Luckily, we caught the problem. Alertness, prayers and the good wishes of one billion Indians helped avert the mission's total failure," the official said.

An issue emerged in the critical cryogenic stage, which is the last stage space vehicles enter just before launch.

Highly flammable liquid hydrogen and oxygen used in the cryogenic stage had to be removed from 'Baahubali' and an errant component was "tightened", the ISRO official told NDTV.

The success of Chandrayaan 2 mission will make India the fourth country after the US, Russia and China to pull off a soft landing on the moon.

'Baahubali', a 640-tonne rocket, is 44 metres long or as tall as a 15-storey building.

The rocket will propel into space an orbiter, a lander 'Vikram' (named after ISRO founder and eminent Indian scientist Vikram Sarabhai) and a moon rover 'Pragyaan'.

A soft landing on the moon, or as ISRO chairman K Sivan terms it, the "fifteen minutes of terror", will then be attempted, after which the rover will carry out research, including a thorough mapping of the moon's resources, looking for the presence of water on the moon and clicking high resolution images as well.

K Sivan has called Chandrayaan 2 the "most complex mission ever undertaken by ISRO".

Considering ISRO's budget is less than 20 times that of USA's NASA, a success story for the Rs 1,000-crore moon mission, which cost less than Hollywood blockbuster 'Avengers: Endgame', would be a giant boost for India's space plans.