Losing the way: On ISRO and issues with its NavIC constellation

NavIC (Navigation with Indian Constellation) is India’s regional satellite navigation system. It was developed to provide accurate position information to users in India and the region extending up to 1,500 km from its boundary, reducing dependence on foreign systems like the U.S. GPS.

For a navigation system to provide accurate 3D position (latitude, longitude, and altitude) and time, a user needs signals from at least four satellites simultaneously. With only three functional satellites, NavIC cannot provide reliable PNT services to users.

The IRNSS-1F satellite, which was launched in 2016, reported a failure in its rubidium atomic clock. This failure is significant because the constellation was already at the bare minimum of four operational satellites, and this loss pushed the number down to three, making the system globally unreliable.

The first generation of NavIC satellites (IRNSS-1A to 1G) used three rubidium atomic clocks each, imported from SpectraTime. However, several of these clocks failed across multiple satellites, forcing ISRO to launch replacement satellites and eventually develop its own indigenous clocks to ensure reliability.

When a satellite is “left in the wrong orbit,” it means the rocket did not put it in the exact path needed for its mission. For navigation satellites, which must stay in specific spots (geostationary or geosynchronous), being in the wrong orbit usually makes the satellite useless for its core mission.

Satellites have a “design life,” which is the amount of time they are planned to operate before their parts wear out or they run out of fuel. While some satellites continue to work past their design life, IRNSS-1F failed almost exactly when its planned life ended.

Out of the 11 satellites launched so far, the 8 inactive ones include models like IRNSS-1A (clock failure), IRNSS-1H (failed to reach orbit), and others that have completed their mission life or developed hardware issues.

After the failure of imported clocks on early NavIC satellites, the Space Applications Centre (SAC) in Ahmedabad developed its own rubidium atomic clock. This was a major step toward technological self-reliance, ensuring that future satellites would not depend on foreign manufacturers for critical components.

NVS-01 was a milestone for ISRO. It was not only the first of the second-generation NavIC satellites but also the first to be equipped with an indigenous rubidium atomic clock, replacing the problematic imported Swiss clocks.

During the 1999 Kargil War, the Indian military needed precise GPS data to target enemy positions. However, the United States denied access to its GPS signals for the region. This incident convinced Indian policy-makers that the country needed its own independent satellite navigation system to ensure national security.

In 2020, India reformed its space sector to allow private participation and created NewSpace India Limited (NSIL) to handle commercial activities. However, without a formal “National Space Law” (like the pending Space Activities Bill), the legal roles and boundaries for agencies like ISRO remain unclear, forcing them to juggle multiple conflicting responsibilities.

Unlike the US and EU, which have dedicated civilian agencies (GPS Directorate and EUSPA) to manage the day-to-day operations and policy of their navigation systems, India relies solely on ISRO. This means ISRO has to build the satellites AND manage their complex daily usage, which is a heavy administrative burden.

Atomic clocks are the most sensitive parts of a navigation satellite. To ensure the satellite keeps working even if one clock fails, engineers use “redundancy” (adding extra backup clocks). By increasing the count from three to five, ISRO aims to make sure each satellite lasts its full 12-year mission even if multiple clocks break down.

NavIC satellites have a limited lifespan. To keep the system working, ISRO must launch “replacement satellites” before the old ones fail. Currently, because ISRO is not launching rockets often enough, the number of working satellites is dropping faster than new ones are being added.

ISRO has a limited budget and workforce, but it must manage many major projects at once. These include the Gaganyaan (human spaceflight), Chandrayaan (moon missions), and various Earth-observation satellites. Because these high-profile missions take up a lot of resources, the routine work of maintaining the NavIC constellation often gets delayed.

With the 2020 reforms, India opened its space sector to private companies. Start-ups like Skyroot Aerospace and Agnikul Cosmos are developing their own rockets. ISRO provides them with technical mentoring and access to its launch pads, but this also takes up time and effort from ISRO’s own scientific staff.

The original NavIC satellites used the L5 and S bands, which most global smartphones and chips did not support. By adding the L1 band in the second-generation (NVS) satellites, India makes its navigation system compatible with the standard chips used in common smartphones, making it much easier for ordinary citizens to use NavIC instead of GPS.

By the end of 2026, ISRO hopes to have a total of six or seven working satellites in the NavIC constellation again. However, the editorial warns that unless the underlying problems (like the lack of a dedicated management agency and the slow launch rate) are fixed first, just launching more satellites might not solve the crisis.