Only three satellites left active: Centre acknowledges NavIC standalone navigation gap 

India’s homegrown satellite constellation NavIC has lost its ability to deliver standalone navigation services after dropping below the critical threshold of operational spacecraft.

Following the end of mission life for IRNSS-1F, the regional system is running on just three active Positioning, Navigation and Timing (PNT) satellites — one short of the four required to pinpoint a user’s position.

The admission came in a written response in the Lok Sabha by Union Minister of State for Space Dr. Jitendra Singh.

"To provide basic positioning service, a minimum of four operational satellites are required in orbit. Hence, the NavIC constellation cannot provide standalone positioning service; however, timing service is functional," Singh said.

Calculating a user's exact latitude, longitude, altitude, and time independently requires signals from at least four visible satellites. At present, the operational constellation relies on just IRNSS-1B, IRNSS-1I, and NVS-01.

Despite the operational shortfall, the government clarified that users face no security or operational vulnerabilities. NavIC functions seamlessly within a multi-constellation Global Navigation Satellite System (GNSS) environment, operating alongside global networks like GPS, Galileo, and GLONASS. The Indian Armed Forces also utilize this hybrid GNSS framework to maintain operational capabilities without interruption.

The current deficit follows recent setbacks in ISRO's second-generation satellite lineup. While NVS-01 launched successfully in 2023, the subsequent NVS-02 mission suffered propulsion glitches that left it unable to reach its intended operational orbit.

ISRO is now moving to rebuild the constellation and restore full independent service across India and regions extending roughly 1,500 kilometers beyond its borders. The NVS-03 satellite is fully prepared for launch, while NVS-04 and NVS-05 are currently in advanced stages of realisation.

What is NavIC?

NavIC (Navigation with Indian Constellation), officially operationalised as the IRNSS (Indian Regional Navigation Satellite System), is India's indigenous satellite navigation system developed by the Indian Space Research Organisation (ISRO).

It is designed to provide accurate position, velocity, and timing (PNT) services to users in India and the surrounding region extending up to 1,500 km beyond the nation's borders.

Core specifications & Capabilities

• Coverage Area: Entire Indian landmass and an area extending up to 1,500 km around the Indian boundary. 
• Accuracy: Better than 10 meters for civilian users across the primary coverage area. Better than 5 meters within the core Indian landmass. 

Service Types

1. Standard Positioning Service (SPS): Open to all civilian users (integrated into modern consumer smartphones and vehicle tracking systems). 
2. Restricted Service (RS): An encrypted signal reserved exclusively for authorized strategic users, such as the Indian Armed Forces and security agencies.

Because NavIC satellites operate in higher GEO and GSO orbits (36,000 km altitude) placed continuously over the Indian region, their signals face minimal blockage from high-rise buildings and mountainous terrain compared to global MEO systems.

India developed NavIC to achieve strategic autonomy in space-based positioning. During the 1999 Kargil conflict, foreign navigation access was restricted over the combat region, highlighting the necessity for a sovereign satellite system for defense applications, critical infrastructure timing, fleet tracking, and disaster management.