New Delhi: The countdown for the Saturday launch of IRNSS-1D, the fourth satellite in the Indian Regional Satellite Navigation Satellite System, began on Thursday at 5:49am.

While Indian Space Research Organisation (Isro) were to launch the satellite on 9 March, the launch was postponed because of an anomaly was found in one of the telemetry transmitters of the spacecraft.

The satellite will be launched onboard Polar Satellite Launch Vehicle (PSLV-C27), the workhorse rocket of the Indian space agency, at 5:19pm on Saturday from Satish Dhawan Space Centre in Sriharikota.

IRNSS is an independent regional navigation satellite system being developed by India consisting of a constellation of seven satellites. It is designed to provide accurate position information service to users in India as well as the region extending up to 1500km from its boundary, which is its primary service area.

The space agency has said that the propellant filling operations for the PSLV-C27 have been completed .

The IRNSS is expected to provide a positional accuracy of better than 20 metres in the primary service area. Three satellites are to be placed in suitable slots in the geostationary orbit, a circular orbit 35,786km above the equator and the remaining four will be placed in geosynchronous, elliptical orbits designed to keep communication satellites within the view of ground stations.

The system will provide two types of services including Standard Positioning Service (SPS) which is provided to all the users and Restricted Service (RS), which is an encrypted service provided only to the authorized users. Some of the applications provided by the IRNSS would be terrestrial, aerial and marine navigation, disaster management, vehicle tracking and fleet management, integration with mobile phones, precise timing, mapping and geodetic data capture, terrestrial navigation aid for hikers and travellers, visual and voice navigation for drivers.

After the launch of a navigational satellite, its solar panels are deployed automatically, and Isro’s master control facility at Hassan, Karnataka, takes control of the satellite. The fifth IRNSS satellite is expected to be launched by September.

The navigational system aims to reduce India’s dependence on foreign systems such as the US global positioning system and the Russian global navigation satellite system. The IRNSS launch will be followed by a commercial satellite launch aboard the PSLV and the GSAT-6 satellite launch aboard the GSLV-D6 with an indigenous cryogenic engine. Before the end of the year, the space agency will launch India’s first dedicated astronomical satellite, ASTROSAT.