ISRO chairman says fleet is fine, trying to revive failed clocks

NavIC, the indigenously built satellite- based positioning system, has developed a technical snag in the atomic clocks on its first satellite.

In the NavIC, a constellation of seven satellites, one of the three crucial rubidium timekeepers on IRNSS-1A spacecraft failed six months ago. The other two followed subsequently.

A. S. Kiran Kumar, Chairman of the Indian Space Research Organisation, confirmed the glitch in the clocks but clarified that the satellite was otherwise all right, and the rest of the satellites were performing its core function of providing accurate position, navigation and time. However, 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, he said, 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.

“There are some anomalies in the atomic clock system on board. We are trying to restart it. Right now we are working out a mechanism for operating it,” he told The Hindu.

“The problem is only with the clock system of one spacecraft. The signals are all coming, we are getting the messages, everything else is working and being used, except the stability portion which is linked to the clock,” he said. A minimum of four working satellites was sufficient to realise the full use of the navigation system”.

NavIC has 21 atomic clocks on seven spacecraft. “How would the other clocks fare? Would ISRO reconsider the supplier of its atomic clocks? Such questions are not easy to answer. Generally any [space] hardware is an issue. We have to find ways of going around it,” he said.

The troubled IRNSS-1A spacecraft was put in space in July 2013 and has an expected life span of 10 years. The seventh navigation satellite, IRNSS-1G, was launched in April 2016.

The satellites of the ₹1,420-crore NavIC, short for Navigation with Indian Constellation, and also known as the Indian Regional Navigation Satellite System, give precise information on position, navigation and time (PNT) of objects or persons to users on ground, sea and air.