ISRO wastes no time in fixing atomic clock issues

Navigation satellite components. Image courtesy of ISRO's Space Application Centre (SAC).

After three atomic clock failures on its IRNSS-1A satellite, rendering the satellite inadequate, the Indian Space Research Organisation (ISRO) has taken steps to remedy the situation.

IRNSS-1A is the first of ISRO’s Indian Regional Navigation Satellite System (IRNSS) satellites for a satellite navigation system known as NavIc. The failures took place in 2016, 3 years after the launch of IRNSS-1A, and involves the malfunctioning of one primary atomic clock and two back-up ones. Including IRNSS-1A, the NavIC constellation currently consists of 7 satellites in orbit.

These atomic clocks were manufactured by Spectracom, a manufacturer of precision time and frequency instruments, and had been integrated with ISRO satellites by India’s Council of Scientific and Industrial Research’s  (CSIR) National Physical Laboratory (NPL). The cause of the failures has not been revealed.

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Over the past few days, ISRO made two announcements to recover from its time-keeping issues.

First, it has set a definite window for the launch of IRNSS-1A’s replacement satellite, IRNSS-1H, which will open in late August. IRNSS-1H will be launched from Sriharikota using the Polar Satellite Launch Vehicle (PSLV), ISRO’s most popular launcher. The satellite has already been delivered to Sriharikota from ISRO’s Space Applications Centre (SAC), Ahmedabad, where it was developed.

Second, it has signed a new Memorandum of Understanding (MoU) with India’s CSIR-NPL, the organization responsible for ISRO’s the integration and tracking of ISRO’s atomic clocks.  Under the new MoU, which will last 5 years, CSIR-NPL will provide time and frequency traceability services necessary for the proper functioning of the IRNSS constellation.

CSIR-NPL is also currently developing an indigenous rubidium atomic clock in collaboration with SAC, based on an announcement made by ISRO Chairman A. S. Kiran Kumar in 2015.

In early June, ISRO and the Israeli Space Agency (ISA) also signed an MoU, which contained an agreement to cooperate on atomic clocks. Israel is one of the world’s leading nations in atomic clock development, with manufacturer Accubeat providing atomic clocks to the U.S. Air Force, Boeing and others, and with Ben-Gurion University designing and producing them in collaboration with Accubeat.


  1. It will be good if SAC-NPL could develop Space qualified Rb atomic clocks for IRNSS.But it appears very unlikely in many many years to come.To put facts straight, before my superannuation we developed two Rb atomic clocks under the joint project and afterwards no progress worth the mention has been made.I am the first Indian scientist who had developed indigenous
    know how of Rb atomic clocks in India.Had this know- how and my expertise been used, India could have by now developed space qualified Rb atomic clocks for IRNSS. There should be a impartial committee to find out why my expertise in this field was not used being the only scientist in field of Rb atomic clock and specially it critical part -the Physics package.Is any one listening to MAKE IN INDIA theme of PM Modi ji !!


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