News Item

Clocks fail on Indian navigation satellite

All 3 clocks have failed on the oldest of the 7 satellites forming the Indian Regional Navigation Satellite System.

The 3 rubidium atomic frequency standards (RAFS) - from the same company that manufactures those in Galileo - have all stopped working, rendering the satellite IRNSS-1A unusable for precise navigation.

The Chairman of the Indian Space Research Organisation (ISRO) confirmed the problem with the clocks, but added that the satellite was otherwise functioning - and the other satellites in the constellation were working. He added however that, without its clocks, IRNSS-1A 'will give a coarse value. It will not be used for computation. Messages from it will still be used.'

He added that ISRO was trying to revive the clocks on 1A and readying one of the 2 back-up satellites to replace it in space in the second half of this year.

The Chairman continued: '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 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. A minimum of 4 working satellites was sufficient to realise the full use of the navigation system.'

IRNSS-1A was launched in July 2013, with an expected life span of 10 years. The 7th and last satellite, IRNSS-1G, was launched in April 2016. 1A is in a geo-synchronous orbit at 55ºE, with an inclination of 29º.

The Swiss firm Spectratime manufactured the clocks and both types of clock - 3 RAFS and 7 passive hydrogen masers - that have failed on Galileo satellites.

Further details from the links below . .

  • 30 January 2017
  • RIN

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