As part of its aspirations to build a regional navigational system equivalent to the GPS of the US, ISRO plans to send seven satellites to put its Indian Regional Navigational Satellite System (IRNSS) in place.

Chennai: The 67-hour countdown for the launch of India's navigation satellite IRNSS 1C began today at the spaceport of Sriharikota. The IRNSS 1C is the third of seven satellites in a series which aims to build an Indian navigation system that will be on par with US' Global Positioning System, on board PSLV C 26.

Following the clearance from the Launch Authorisation Board (LAB) yesterday, the countdown commenced at 6.32 am today as planned and was proceeding smoothly, Isro said.

Based on the mission requirements, the launch window is 01:32 AM to 01:47 AM (IST) on 16 October. The lift-off is scheduled at the opening of the launch window at 1.32 am, the national space agency had earlier announced.

The earlier planned launch on 10 October was postponed due to technical reasons.

IRNSS 1C with a lift-off mass of 1,425.4 kg will be shot into a sub Geosynchronous Transfer Orbit (sub GTO).

As part of its aspirations to build a regional navigational system equivalent to the Global Positioning System of the US, ISRO plans to send seven satellites to put its Indian Regional Navigational Satellite System (IRNSS) in place.

The first two satellites in the series, IRNSS 1A and IRNSS 1B were launched from Sriharikota on 1 July 2013 and 4 April this year respectively.

ISRO needs to launch at least four of the seven satellites to start operations of the IRNSS, ISRO officials said.

Being developed by India, IRNSS is designed to provide accurate position information service to users in the country as well as the region extending upto 1,500 km from its boundary, which is its primary service area.

IRNSS's applications include terrestrial and marine navigation, disaster management, vehicle tracking and fleet management.

IRNSS is similar to US' Global Positioning System, Russia's Glonass and Europe's Galileo.

China and Japan also have similar systems - Beidou and Quasi Zenith.

PTI