CHENNAI:  The 67-hour countdown for the launch of India's third navigation satellite is progressing smoothly though a thunder storm Wednesday delayed some operations, a senior space agency official said.

" We moved the mobile service tower (MST) backwards. The operation was delayed by around two hours owing to thunderstorm in the morning. There is sufficient time cushion built in for such unforeseen delays in the countdown period," M.Y.S. Prasad, director, Satish Dhawan Space Centre at Sriharikota, told IANS.

"At 10 p.m., based on the climatic conditions like thunderstorm, we will decide on the launch. Currently everything is normal," he added.

Prasad said the filling of propellants in the second stage/engine would be completed by 2 p.m.

Following that the gases in the various stages would be pressurised.

At 1.32 a.m. Thursday, Indian rocket Polar Satellite Launch Vehicle (PSLV-C26) carrying the 1,425-kg third Indian navigational satellite badged as Indian Regional Navigation Satellite System-1C (IRNSS-1C) will kiss final goodbye to Mother Earth.

The 44.4 metres tall rocket, weighing around 320 tonnes is expected to spit out the satellite into the space around 20 minutes after the blast-off.

Once the satellite is successfully placed in its orbit, India will be just one more satellite away from having its own satellite based navigation system.