The 44-metre-tall Polar Satellite Launch Vehicle-XL (PSLV-XL) weighing 320 tonnes at lift-off is a four-stage rocket powered by solid and liquid propellants alternatively will blast off from Sriharikota at 11.41 pm.
ISRO has been launching satellites either late evening and early morning. But this is the first time ISRO is launching a satellite around midnight.
The 64.5 hour countdown began at 7.11 am on Saturday.
The launch time has been fixed taking into account the orbit and inclination at which the satellite will be injected into the space.
India's first navigational satellite the IRNSS (Indian Regional Navigational Satellite System)-1A is a 1,425 kg payload.
Around 20 minutes into the launch, the rocket PSLV-XL will eject the navigational satellite at an altitude of 501 km.
The satellite is intended to provide terrestrial, aerial and marine navigation services and help in disaster and fleet management.
The satellite with a life span of around 10 years is one of the seven satellites constituting the IRNSS space system (total cost of Rs 14.2 billion rupees) -- a regional navigational system developed by India to provide accurate position information to users within the country and up to 1,500 km from the nation's boundary. The accuracy of the location could be between 10 meters to 20 meters.
The next one, IRNSS-1B, is due in early 2014 and the full constellation is planned to be completed in 2015. The services cannot begin until the other navigation spacecraft are also up in orbit.
India's push for its own navigation system follows that of China, whose Beidou (Compass) system's global coverage rivals the GPS footprint. Europe has been promoting its Galileo satellite navigation system. US already has a system called Global Positioning System (GPS) with 24 satellites. Russia has GLONASS system with 21 satellites.
The IRNSS will provide two types of services -- standard positioning service for all users and restricted service for authorised users.