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ISRO’s clock to prop up India’s own GPS

Time is running out for the seven-satellite Indian Regional Navigation Satellite System (IRNSS), also known as NavIC (Navigation in Indian Constellation). NavIC, whose seventh satellite was launched in April 2016, was expected to provide India a satellite-based navigation system independent of the U.S.-controlled GPS (Global Positioning System). But India’s own ‘regional GPS’ is yet to become officially operational owing to repeated failures of the atomic clocks on the satellites.

In view of the cascade of failing imported atomic clocks — nine out of the 21 clocks in the fleet have failed — ISRO has decided to add buffers to the NavIC by adding four more satellites. It hopes to have an indigenous atomic clock in each of them. “We are in the process of getting approval [from the government] for at least another four IRNSS satellites,” ISRO Chairman K.Sivan told The Hindu, confirming the failure of clocks. “However, they will have some advanced technology, apart from the atomic clocks developed by ISRO.” NavIC is meant to give Indian civil and military users reliable location and time information, for which the performance of the atomic clocks is critical.

The indigenous atomic clock is being developed by the Space Applications Centre, Ahmedabad, Mr. Sivan said, adding that once it passes qualification tests, “We will first demonstrate the indigenous clock in an upcoming navigation satellite, along with the imported ones. Work on them is going on in full steam.”

The cost and timing of the new satellites are not finalised, Mr. Sivan said. The development and eventual use of an indigenous atomic clock, at a cost of a few hundred crore rupees, was part of the NavIC concept, he added.

First failures in 2016 ::

The rubidium atomic clocks from Europe started failing on the first navigation satellite, IRNSS-1A, around 2016, soon after ISRO put the last and seventh satellite in orbit. Until a few months ago, three more satellites were said to have suffered “one or two dysfunctional clocks” each, while two satellites did not have any problematic clocks. Each satellite carries three atomic clocks, including a standby.

ISRO is concerned that if more clocks fail, it may render the ₹1,400-crore fleet a dud in space. NavIC, which will be controlled solely by India, unlike the American GPS or Russian Glonass navigation systems, will be useful as navigation aids for the armed forces.

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