The countdown for the lift of an Indian rocket with the country’s fourth navigation satellite as the sole passenger began, the ISRO said.

According to Indian Space Research Organisation (ISRO), the 59 and half hours countdown for the launch of rocket Polar Satellite Launch Vehicle (PSLV–27) carrying Indian Regional Navigation Satellite System-IRNSS-1D began in the Sriharikota rocket port in Andhra Pradesh.

The rocket is expected to blast off at 5.19 p.m. on March 28 to put into orbit the 1,425 kg IRNSS-1D satellite.

India has so far launched three regional navigational satellites as part of a constellation of seven satellites to provide accurate position information service to users across the country and the region, extending up to an area of 1,500 km.

Though the full system comprises of nine satellites – seven in orbit and two on the ground as stand-by – the navigation services could be made operational with four satellites, ISRO officials said.

Each satellite costs around Rs.150 crore and the PSLV-XL version rocket costs around Rs.130 crore. The seven rockets would involve an outlay of around Rs.910 crore.

The entire IRNSS constellation of seven satellites is planned to be completed this year itself.

The first satellite IRNSS-1A was launched in July 2013, the second IRNSS-1B in April 2014 and the third on October 16, 2014.

Once the regional navigation system is in place, India need not be dependent on other platforms.