In its 100th launch, the Indian Space Research Organisation (ISRO) is geared to send off a 2,250-kg navigation satellite on-board GSLV-F15 from Sriharikota on January 29 at 06.23 am, the space agency said. The NVS-02 is the second of the five second-generation satellites developed by the space agency to replace the existing satellites in the country’s navigation constellation Indian Regional Navigation Satellite System. The new generation of satellites have a longer lifespan of 12 years and are also equipped with indigenously developed, more accurate atomic clocks. The new generation of satellites also utilise L1 frequency, which is most commonly used in the US Global Positioning System (GPS), and is likely to lead to more utilisation by smaller devices such as fitness trackers. The launch on January 29 will be the 17th flight of the GSLV vehicle, with the 11th flight using the indigenously developed cryogenic engine. The mission will last just over 19 minutes, with the satellite being injected into a 170 x 36,577 km Geostationary Transfer Orbit — an orbit that satellites use to go into the high geostationary orbit. IRNSS — sometimes referred to as NavIC or Navigation with Indian Constellation — is a seven satellite system that provides positioning, navigation and timing services over the Indian mainland and 1,500 km in its neighbourhood. The first satellite in the constellation IRNSS-1A was launched in 2013, with a mission life of 10 years. The next two satellites IRNSS-1B and 1C were launched in the subsequent years. Replacements were needed for some of the satellites in the constellation even before the end of their mission life since the atomic clocks on-board the satellites malfunctioned. A satellite-based positioning system determines the location of objects by accurately measuring the time it takes for a signal to travel to and from it using the atomic clocks on board. The constellation, however, ran into more trouble. One of the replacement satellites IRNSS-1H did not make it to orbit after the heat shield on ISRO’s most reliable launch vehicle PSLV failed to open. There were also criticisms that the services of the navigation constellation were not being optimally utilised. A 2018 report by the CAG said that even though the Cabinet cleared funding of `200 crore to develop user receivers in 2006, work on the project started only in March 2017, by which time seven launches had already taken place. And, several years of mission life of the initial satellites had been wasted. Since then, however, several receivers and applications for the navigation constellation have been developed. With cellphone chipsets capable of receiving IRNSS data becoming available, several of the new phones are capable of using signals from the Indian constellation. The first of the new generation of navigation satellites was launched in May last year by the same launch vehicle.
