Navigation Indian Constellation (NavIC) is an independent Indian satellite-based positioning system for critical national applications. The purpose is to provide “reliable position, navigation and timing services over India and its neighbourhood.” NavIC consists of a constellation of seven satellites and was named so by Prime Minister Narendra Modi.
Three of the satellites are in a geostationary orbit and four in a geosynchronous one. This means they will be visible at all times in the Indian region. All the seven satellites of NavIC, namely, IRNSS-1A, 1B, 1C, ID,1E, 1F and 1G were successfully launched on July 2, 2013, April 4, 2014, Oct. 16, 2014, March 28, 2015, Jan. 20, 2016, March 10, 2016 and April 28, 2016 respectively.
Because navigation requires the most accurate clocks, the ₹1,420-crore NavIC relies on rubidium clocks. Each of the seven satellites has three of them on-board. However, this January, the Indian Space Research Organisation confirmed that the clocks on the first satellite, IRNSS-1A had failed on June 2016.
According to the Indian space agency, the applications of IRNSS are: terrestrial, aerial and marine navigation, vehicle tracking and fleet management, terrestrial navigation for hikers and travellers, disaster management, integration with mobile phones, mapping and geodetic data capture and visual and voice navigation for drivers. Though six of the satellites are working fine, the one, faulty one means the “GPS” isn’t working as accurately as it ought to be.
A. S.Kiran Kumar, Chairman, Indian Space Research Organisation, told the Hindu that without its clocks, the IRNSS-1A “will give a coarse value. It will not be used for computation. Messages from it will still be used.”
ISRO was trying to revive the clocks on 1A and readying one of the two back-up navigation satellites to replace it in space in the second half of this year. Rubidium clocks were the previous standard in accurate clocks and most organisations, that need precise time estimates, need cesium clocks. It is learnt that future clocks on such satellites, each with a lifespan of 10 years, will host such clocks.
