Story of NavIC: crucial indigenous SatNav system, a few hurdles in development path

An indigenous seven-satellite constellation serving both defence and civilian needs was proposed to be put in place by 2016, and the first satellite, IRNSS 1A, was launched on July 1, 2013.

Eleven years later, however, only five of the 11 satellites launched in the Rs 2,250 crore NavIC program – including replacements for failed satellites – are fully operational, the Indian Space Research Organisation (ISRO) has said.

After IRNSS-1A in 2013, the IRNSS-1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, and 1K were launched between April 4, 2014 and January 29, 2025. Following the launch of IRNSS-1G, the seventh in the series on April 28, 2016, ISRO had said that “the successful launch… [of the satellite] signifies the completion of the IRNSS constellation”.

What went wrong with the satellites?

Mid-2016 onward, there were reports of failures of the rubidium atomic clocks used in several navigation satellites, including ISRO’s IRNSS and the European Space Agency’s (ESA’s) Galileo Global Navigation Satellite System (GNSS). There are three atomic clocks on each IRNSS satellite.

Then ISRO chairman A S Kiran Kumar announced in July 2016 that all the atomic clocks on IRNSS 1A had “stopped working”, even though the “overall performance of our navigation system” had not been affected, and the “rest of the satellite components [were] functioning perfectly”. A replacement satellite, IRNSS 1H, with modified clocks, would be launched in 2017, the space agency said.

An ISRO satellite navigation program official had said at the time that “six of the seven IRNSS satellites that were launched [until April 2016] are still working”, but there were “inherent hardware related problems on the rubidium atomic clocks in some of these satellites”. The clocks used in the Galileo system had developed similar problems, the official had said.

The atomic clocks on four other IRNSS satellites – 1C, 1D, 1E, and 1G – also developed problems subsequently. The engine failure on the IRNSS-1K (or NVS-02) launched last month, which has left it in a sub-optimal orbit around Earth, means that six of the 11 IRNSS satellites launched so far have been partial failures.

Also, the IRNSS-1H, launched on August 31, 2017 to replace the IRNSS-1A, did not reach the desired orbit after a heat shield protecting the satellite on board the PSLV-C39 rocket did not detach during the launch.

So how many satellites in the NavIC system are operational currently?

It is estimated that only four IRNSS satellites are fully operational currently – 1B, 1F, 1I (the replacement for 1A after the launch of 1H, the original replacement, failed), and 1J (the replacement for the partially failed 1G).

ISRO’s 2023-24 annual report says that following the launch of NVS-01 on May 28, 2023, five NavIC satellites are operational – IRNSS-1B, 1C, 1F, and 1I, and NVS-01 (IRNSS-1J). However, according to some estimates, 1C is only partially operational due to the presence of the old series of atomic clocks that were reported to be malfunctioning.

First-generation IRNSS satellites launched after July 2016 – that is, 1H and 1I – carried modified versions of the original clocks provided by a European supplier under a Euro 4 million deal for an estimated 45 clocks.

1J, which is operational, and 1K, which reported an engine failure last month, belong to the next generation of IRNSS satellites, and are, on that account, called NVS-01 and NVS-02 respectively. These satellites are equipped with a mix of indigenous and foreign clocks instead of the defective clocks used in the first generation satellites.

Why is the IRNSS/ NavIC system important for India?

The NavIC satellites provide two types of services – Standard Positioning Service which is for general and commercial use, and Restricted Service which is meant for the defence forces – over the Indian landmass and neighbouring regions.

According to A S Ganeshan, a former director of ISRO’s Satellite Navigation Program, the indigenous system provides positioning data “at all times with position accuracy better than 20 metres during all weather conditions, anywhere within India and a region extending about 1,500 km around India on dual frequencies in L5 and S band”. (‘Benefits of an Indian Navigation System’, Science and Culture, 2017)

A primary reason to develop an indigenous satellite navigation system like the IRNSS despite the existence of global systems such as the GPS (US), GLONASS (Russia), Galileo (Europe), Beidou (China), and QZSS (Japan), is the reliability that it offers in defence use.

“Since the first Global NSS systems (GPS and GLONASS) were primarily developed for military purposes, the military applications are one of the drivers for these systems. …GPS offers encrypted Precise Positioning Service which is available only to the US military and its allies. GNSS is used for different types of military applications such as military navigation and target acquisition,” Ganeshan wrote.

For NavIC to become ubiquitous in the Indian subcontinent, ISRO will have to sell its capabilities to general positioning service providers such as mobile phone and vehicle manufacturers, etc.

In December 2023, a few months after the successful launch and deployment of the NVS-01 (IRNSS-1J) satellite on May 29, 2023, the American mobile communications chipmaker Qualcomm reported an agreement to incorporate NavIC support in some of its chipsets.

The partial failure of NVS-02 (1K) notwithstanding, ISRO plans to launch three more second-generation NavIC satellites – NVS-03, 04, and 05 – “to augment NavIC base layer constellation with enhanced features for ensuring continuity of services”.