Sriharikota: India's own navigation system has been running short of satellites for months. On Friday night, ISRO will try to fix that.
The GSLV-F18 rocket is scheduled to lift off at 11.51 pm from the second launch pad at the Satish Dhawan Space Centre, carrying NVS-03. The 24-hour countdown began at 11.51 pm on Thursday.
It is the 20th flight of the Geosynchronous Satellite Launch Vehicle. The 50-metre, three-stage rocket, with a lift-off mass of 420 tonnes, will place the 2,232-kg satellite in a geosynchronous transfer orbit with a perigee of 170 km, an apogee of 37,023 km and an inclination of 20.75 degrees.
This time ISRO is doing something it has not done before: NVS-03 will fly with its pyrotechnic valves already open. Standard practice isolates spacecraft propellant during the vibrations of lift-off, and the change was cleared at the Mission Readiness Review specifically to bypass the connector failure that left NVS-02 stranded in January 2025, when the drive signal never reached the pyro valve in the oxidiser line of the orbit-raising engine. Corrective measures recommended by a high-level committee have been built into this flight.
The satellite carries an indigenous rubidium atomic clock developed by the Space Applications Centre, alongside procured clocks. It will transmit in the L1, L5 and S bands. Adding L1 matters for civilians: it is the frequency most smartphone chipsets and wearables use.
NavIC is thin on the ground right now. Only three satellites are providing navigation signals — IRNSS-1B, IRNSS-1I and NVS-01 — against a minimum of four needed to fix a position. Minister Jitendra Singh told the Lok Sabha on July 29 that the constellation therefore "cannot provide standalone positioning service, however timing service is functional".
If NVS-03 reaches its slot and is validated, that count returns to four. ISRO chairman V Narayanan, speaking after prayers at Tirumala on Thursday, called it the fifth mission of the year and said India would then have four operational navigation satellites, including one with an indigenous atomic clock.
The launch is only half the job. The rocket leaves the satellite in an elongated transfer orbit, and NVS-03 must fire its own engine to climb to its geosynchronous slot at 32.5 degrees East. That manoeuvre is exactly where NVS-02 failed.