Why in news?

India’s regional navigation system NavIC has faced another setback after the atomic clock onboard the IRNSS-1F satellite stopped functioning, leading to the loss of its positioning data.

Although the satellite will still provide messaging services, atomic clocks are essential for accurate navigation signals used in mapping, vehicle navigation, and infrastructure planning. The issue is compounded by the NVS-02 replacement satellite failing to reach its final orbit, further affecting the system’s positioning capability.

What’s in Today’s Article?

• About IRNSS or NavIC
• Status of NavIC Satellites Providing Positioning Data
• NVS-02 Satellite and Its Failure
• Global Satellite Navigation Systems

About IRNSS or NavIC

• The Indian Regional Navigation Satellite System (IRNSS), also known as Navigation with Indian Constellation (NavIC), is India’s satellite-based navigation system designed to provide positioning services over India and up to 1,500 km beyond its borders.
• NavIC was planned as a seven-satellite constellation, similar in concept to the U.S. Global Positioning System (GPS), to deliver reliable navigation and timing information across the region.
• When fully operational, NavIC is designed to provide location accuracy of about 10 metres over India and neighbouring areas.
• Because its satellites are positioned directly above the region, signals are stronger and more reliable in challenging terrains such as valleys and forests.
• Despite its strategic importance, the NavIC system has faced technical issues since its inception, affecting the consistent availability of accurate positioning services.

Status of NavIC Satellites Providing Positioning Data

• After the 2023 launch, five satellites in the NavIC constellation were capable of providing positioning data: IRNSS-1B, IRNSS-1C, IRNSS-1F, IRNSS-1I, and NVS-01 (a new-generation NavIC satellite).
• With the failure of the atomic clock on IRNSS-1F, the satellite can no longer provide positioning data, reducing the number of operational satellites in the system.
• Many early NavIC satellites are approaching or exceeding their design life.
  • IRNSS-1A (2013) is almost defunct due to earlier atomic clock failures.
  • IRNSS-1B and IRNSS-1C, launched in 2014, have also crossed their 10-year mission life.
• ISRO attempted to maintain the constellation through replacement missions:
  • IRNSS-1H (2017) failed to reach orbit after the heat shield did not open.
  • IRNSS-1I (2018) was successfully launched later as a replacement satellite.

NVS-02 Satellite and Its Failure

• NVS-02, the second satellite of the new-generation NavIC series, was launched in January 2025 aboard GSLV-F15 during ISRO’s 100th mission and placed in a highly elliptical transfer orbit.
• The satellite failed to move into its intended operational orbit due to an electrical malfunction that prevented the engine from igniting.
• A review committee found that the signal required to activate the pyro valve in the oxidiser line did not reach the engine.
  • This likely occurred because a connector contact disengaged, breaking the electrical circuit.
• Delays in Developing the User Segment
  • The NavIC programme has also faced criticism for delays in developing user receivers.
  • A 2018 CAG report noted that although funding was approved in 2006, work began only in 2017, by which time several satellites had already been launched.
  • Despite these setbacks, NavIC services are already used in aviation, shipping, and railways, and many modern smartphones support NavIC signals alongside GPS and GLONASS.

Advancements in New-Generation NavIC Satellites

• Indigenous Atomic Clocks - A key upgrade is the development of indigenous atomic clocks by ISRO, reducing dependence on foreign systems and addressing earlier failures that affected positioning accuracy.
• Importance of Atomic Clocks - Satellite navigation relies on precise time measurement to calculate location. Failures in atomic clocks previously disrupted accurate positioning, making this upgrade crucial for reliability.
• Extended Mission Life - The new-generation satellites have an extended lifespan of 12 years, compared to 10 years for earlier satellites, ensuring longer operational stability.
• Addition of L1 Frequency Band - Along with existing L5 and S bands, new satellites transmit in the L1 frequency, which is widely used by global systems like GPS.
• Improved Interoperability and Usability - The inclusion of the L1 band enhances compatibility with global navigation systems and enables usage in low-power devices like smartphones and smartwatches, expanding NavIC’s applications.

Global Satellite Navigation Systems

• There are four primary global navigation satellite systems (GNSS):
  • US – GPS (Global Positioning System)
  • Russia – GLONASS
  • Europe – Galileo
  • China – BeiDou
• These systems provide worldwide positioning, navigation, and timing services.
• Regional Navigation Systems
  • Some countries operate regional systems:
    • India – NavIC (IRNSS) with 7 satellites
    • Japan – QZSS (Quasi-Zenith Satellite System) with 4 satellites, mainly augmenting GPS over Japan
  • Orbital Configurations
    • GPS, GLONASS, Galileo: Over 20 satellites each in Medium Earth Orbit (~20,000 km)
    • BeiDou: Over 40 satellites in mixed orbits (Medium Earth + Geosynchronous ~35,000 km)
    • India and Japan systems: Fewer satellites placed in Geosynchronous orbits, optimised for regional coverage
    • Global systems ensure worldwide coverage, while regional systems like NavIC and QZSS are designed for higher accuracy within specific geographic areas.