On April 4, India’s Polar Satellite Launch Vehicle (PSLV) marked its 25th consecutive successful mission by lofting the second spacecraft required for the Indian Regional Navigation Satellite System (IRNSS). The IRNSS will function much like America’s widely-used Global Positioning System (GPS), albeit on a regional scale. The GPS is based on a constellation of 24 satellites that transmit signals, which suitably equipped receivers pick up and utilise to establish their position with a great level of accuracy. Originally intended for the U.S. armed forces, the use of unencrypted GPS signals have spawned a wide range of civilian applications. Vehicles, aircraft and ships increasingly rely on equipment with satellite navigation capability. Smartphones and other mobile devices providing map and location-based services too take the aid of GPS signals. Russia has a similar satellite system in place, called GLONASS. Europe is in the process of establishing a navigation satellite system of its own, named Galileo. China’s BeiDou Navigation Satellite System began offering regional services in December 2012 and is expected to achieve global coverage by around 2020. Japan wants to create a satellite system to improve GPS coverage over that country.

The IRNSS, being wholly under Indian control, serves an important security requirement — making sure that so critical a service is available at all times. Military operations have come to rely on satellite navigation and there is no guarantee that another country’s system will be accessible during a crisis situation. To keep costs down, the Indian Space Research Organisation has opted for a constellation of just seven satellites to provide accurate navigation signals over India and up to 1,500 km from its borders. The first of those satellites, IRNSS-1A, was launched in July last year. The performance of that satellite has been extensively analysed and found to be very satisfactory. The second satellite, IRNSS-1B, has now been put into orbit, and two more will follow later this year. Once the four IRNSS satellites are up and functioning, it will be possible to ascertain whether the system’s signals provide the required positional accuracy. The remaining three satellites are to be launched by the middle of next year. The option exists to extend the coverage area by adding four more satellites. ISRO is working with industry so that receivers that utilise the IRNSS signals become available. Some of these receivers will be capable of taking signals from other navigation satellite systems as well, like the GPS. The use of IRNSS must extend well beyond India’s security services, and ISRO will need to take the lead in promoting the widespread utilisation of the system.

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