As ISRO launch fails, glitch in space waits for fix

As ISRO launch fails, glitch in space waits for fix

The Indian Express explains what went wrong with the launch of IRNSS-1H, and what it was meant to do

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The IRNSS-1H spacecraft integrated with PSLV-C39 (Photo source: ISRO)

What went wrong in the launch of the IRNSS-1H satellite by ISRO Thursday?

ISRO declared the IRNSS-1H launch a failure after a heat shield failed to separate, preventing the satellite from being deployed in space by PSLV-C39, the launch vehicle. The performance of PSLV-C39 went to plan up to the point when the satellite had to be inserted in orbit. “During the operation the heat shield has not separated. Further analysis will be carried out subsequently,” said ISRO’s range operation director at the Satish Dhawan Space Centre in Sriharikota.

What is a heat shield?

The heat shield is a protective cover provided around the satellite to help it withstand the adverse temperatures felt when a rocket is launched into space. Separation of the heat shield occurs mid-flight when the rocket leaves Earth’s atmosphere.

What was IRNSS-1H supposed to do?

IRNSS-1H was the eighth in a series of IRNSS (Indian Regional Navigation Satellite Systems) satellites launched by ISRO since July 2013. This was to create a constellation to provide satellite-based navigation services over the Indian subcontinent on the lines of the global positioning system (GPS) created by the United States. The Indian navigation satellite constellation, called NavIC, essentially comprises seven satellites. IRNSS-1H was intended to replace IRNSS-1A, which developed problems last year. IRNSS-1H would have augmented “the existing seven satellites of NavIC constellation”. It was supposed to sit in a sub-Geosynchronous Transfer Orbit (sub-GTO).

What kind of problems made a replacement necessary?


ISRO stated last January that three Rubidium Atomic Frequency Standard (RAFS) clocks on IRNSS-1A, the first satellite launched on July 1, 2013, had developed problems, rendering the satellite ineffective for navigation services. “Three atomic clocks of IRNSS-1A have stopped working. But the rest of satellite components are functioning perfectly. In fact, we are using this satellite for messaging activity. The stopping of these atomic clocks has not affected the overall performance of our navigation system. We are planning to launch a replacement satellite,” ISRO chairman A S Kiran Kumar had said.

After the failed launch, what can ISRO do?

IRNSS-1H was among nine satellites (seven for the navigation service, two backup) indented at Rs 1,420 crore for IRNSS. ISRO has one more satellite in its kitty. A new satellite could be launched in the next few months to make up for the loss. ISRO chairman Kumar has also hinted in recent times that the constellation could go up to 11 satellites. In that case, more satellites could be built and launched.

Also read | ISRO launch fails after heat shield does not detach

How do these satellites work?

IRNSS is intended to provide two services — Standard Positioning Service for general users and a Restricted Service, which is an encrypted service only for authorised users like the defence forces. NavIC is designed to provide accurate position information services to users in India as well as the region, up to 1,500 km from the boundary. For NavIC to become ubiquitous in the subcontinent, ISRO will sell its capabilities to general positioning service providers like mobile phone manufacturers, vehicle manufacturers etc.

Couldn’t existing satellite systems have provided such services?

One of the primary reasons for the development of the indigenous Indian system despite the existence of global systems — the American GPS, the Russian GLONASS, the European Galileo, the Chinese BeiDou — is the reliability that it offers when used for defence purposes. ISRO started work on the IRNSS programme in 1999 after the Kargil War, where Indian defence forces could not use American GPS in the conflict zone to locate its soldiers.

What is the payload on IRNSS-1H?

Like the previous satellites in the series, IRNSS-1H had a navigation payload and a ranging payload. The ranging payload of IRNSS satellites has a C-band transponder to determine the range of the satellite. The navigation payload is meant to transmit navigation service signals to users on earth while operating in the L5-band and S-band. Part of the navigation payload is high-accuracy RAFS clocks.

Why are these clocks important?

Atomic clocks are a key component in a navigation system. The ISRO satellites are equipped with three clocks each — one clock being the primary timekeeper and two acting as backup. On IRNSS-1A, all three clocks had failed. Accurate timekeeping lies at the heart of navigation systems since the determination of a person’s position on earth is subject to the accurate calculation of delays in signal transmission from the satellite to earth. “The critical point of a satellite navigation system are the clocks on board. Because they are so important there is more than one clock on board. They are necessary because if you don’t have the right clocks and even if you don’t consider the relativity theory of Einstein the error would be more than 500 metres in one hour,’’ states the European Space Agency on its website.

What went wrong with the clocks?

The problems were similar to those reported last January by the European Space Agency. Three RAFS clocks supplied by an European manufacturer, Spectratime, which were used by the ESA for its Galileo satellite navigation system, developed problems. No satellite in the 18-satellite Galileo system, however, was lost by the ESA since backup clocks remained operational. “These failures seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground,” ESA stated in January this year.

How has ISRO addressed the problems with the IRNSS clocks?

The atomic clocks in new satellites are modified versions of the original clocks provided by Spectratime under a 4-million-euro deal signed in 2008. ISRO has been carrying out modifications of clocks procured from Spectratime to overcome technical issues.

Who built IRNSS-1H?


A consortium led by Alpha Design Technologies, a defence equipment supplier from Bengaluru, built it over eight months. The Rs 400-crore company was tasked with making two satellites. The second is expected to be complete by April 2018. Alpha Designs was assisted by a team of 70 ISRO scientists.