The two more navigation satellites will be launched during the second half of 2014.
Prior to that, ISRO will be launching the French satellite SPOT-7 and four other foreign satellites in a PSLV rocket and also test its heavier rocket - the Geosynchronous Satellite Launch Vehicle (GSLV) Mark III version, said Radhakrishnan.
The IRNSS-1B satellite with a design life span of 10 years will be part of the seven-satellite Indian regional navigational system. The first navigational satellite IRNSS-1A was launched in July 2013.
The navigational system, developed by India, is designed to provide accurate position information service to users within the country and up to 1,500 km from the nation's boundary line.
The system is similar to the global positioning system of the US, Glonass of Russia, Galileo of Europe, China's Beidou or the Japanese Quasi Zenith Satellite System.
The system will be used for terrestrial, aerial and marine navigation, disaster management, vehicle tracking and fleet management, integration with mobile phones, mapping and geodetic data capture and others.
While the ISRO is silent on the navigation system's strategic application, it is clear that the IRNSS will be used for defence purposes as well.
According to the ISRO, the IRNSS-IB has been realised within seven months of the launch of the IRNSS-1A.
Satish Dhawan Space Centre (SDSC)-SHAR director M.Y.S.Prasad told IANS: "Even if a navigation system has more than four satellites, the final precise data is picked from four satellites."
Meanwhile Indian space agency officials are getting ready for the 58 and half hour launch countdown slated to begin April 2 around 6.45 a.m.
"Normally 53 hour countdown is sufficient. But we have decided to an extended countdown so that some break time could be given for the officials," Prasad said.
On the issue of INSAT-3E satellite, Radhakrishnan said the satellite was launched in 2003 and its life span has come to an end.
"Users are being migrated to other satellites," he said.
