ISRO launches its fourth navigational satellite IRNSS-1D

The Indian Space Research Organisation (Isro) today successfully launched the country's fourth navigational satellite, IRNSS-1D, from the Satish Dhawan Space Centre at Sriharikota, about 90 km from Chennai.

The satellite was launched onboard Isro's workhorse PSLV-C27, taking India closer to having its own navigation system.

The 44.4 metre tall PSLV-C27, which has a lift off mass of 1,425 kg, will put the satellite in a geosynchronous orbit at 111.75 degree east longitude with 30.5 degree inclination.

The launch, originally scheduled for 9 March, had to be delayed after an anomaly was found in a telemetry transmitter.

IRNSS-1D is the fourth in the series of seven satellites, planned by Isro to put in place the Indian Regional Navigation Satellite System (IRNSS), currently under development.

Isro plans to follow this up with two more launches this year and a third next year, completing the seven-satellite regional navigational system.

The IRNSS system is unique as it consists of only seven satellites while other systems have more than 20 satellites. While other systems are global, Indian system is regional in nature.

The Indian Regional Navigational Satellite System, when fully operational, would replace the US global positioning system (GPS), Isro officials claim.

The fully operational system is expected to provide accurate position information service to users across the country and the region, extending up to an area of 1,500 km.

The seventh and the last one of the Indian Regional Navigation Satellite System in all probability would go up in the early part of 2016.

Full navigation services are expected to be offered from mid 2016 onwards, according to the officials.

The system would provide two types of services - Standard Positioning Service, which is provided to all the users, and Restricted Service that is an encrypted service provided only to authorised users.