3 atomic clocks fail on 1 Indian satellite, replacement prepped

IRNSS-1B, launched April 4, 2014.

Three atomic clocks onboard a single satellite of the NAVIC Indian regional navigation satellite system have failed.

Indian Space Research Organization (ISRO) Chairman A.S. Kiran Kumar told The Hindu newspaper that the agency is trying to restart the clocks. Kumar said the affected satellite, IRNSS-1A, is otherwise healthy, and the rest of the constellation is performing its core function of providing accurate position, navigation and time.

Last week, the European Space Agency discussed clock failures on board Galileo satellites. Rubidium atomic clocks onboard both constellations were manufactured by Spectratime of Switzerland, but the cause of the failures has not been identified and could involve factors other than clock design.

IRNSS-1A is equipped with one primary and two back-up clocks. At this time, it “will give a coarse value. It will not be used for computation. Messages from it will still be used,” Kumar said. “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.”

The ISRO is readying one of the two back-up navigation satellites — IRNSS-1H — to replace it in space in the second half of this year. IRNSS-1A was launched in July 2013 and has an expected lifespan of 10 years.

The Indian Regional Navigation Satellite System (IRNSS) constellation was completed April 28, 2016. It was then renamed NAVIC — Navigation Indian Constellation, by India’s Prime Minister Narendra Modi.

With seven satellites in orbit, the constellation’s primary focus is to provide information in the Indian region and 1,500 kilometers around the mainland.