Indian space agency ISRO’s latest navigation satellite, NVS-02, will not reach geostationary orbit because a pyro valve, meant to let in the oxidiser, failed to open. Without the oxidiser, the fuel will not burn. This sets the clock back not only on the ‘Navigation with Indian Constellation’ (NavIC) programme but also ISRO’s human space flight mission, Gaganyaan.
The NVS-02 cost ₹300 crore; another ₹300 crore was spent on the GSLV rocket. Because of the unopened valve, ISRO cannot steer the 2,250 kg satellite from its elliptical geosynchronous transfer orbit (GTO) to the circular geostationary orbit, where it was meant to be positioned above a chosen region on earth at all times.
ISRO is now saying that all is not lost, and the satellite could still be nudged up to some extent; moreover, if this too fails, then the satellite could be repurposed. However, experts note it could, at best, be used for testing the performance of the onboard India-made atomic clock and for messaging services.
Chequered history
ISRO, which has tasted success with several missions, has not been so lucky with NavIC.
India decided to develop its own satellite navigation system — NavIC — for strategic reasons because, as it found out during the Kargil war, access to global systems is uncertain. Originally called Indian Regional Navigation Satellite System (IRNSS), NavIC is meant to provide accurate position information service to users across India and its 1,500-km neighbourhood.
NavIC is designed to provide two types of services — standard positioning service (SPS) with accuracy greater than 20 metres and timing accuracy of 20 nanoseconds for civilian use; and a restricted service (RS), which is encrypted and offered only to authorised users.
The first navigation satellite, IRNSS-A, was orbited in 2013 and others — IRNSS-1B to -1L — followed until 2018. Trouble started with the first satellite, when the imported atomic clocks failed. Subsequently, the atomic clocks in a few other satellites, too, failed.
Another setback was in 2017, when the IRNSS-1H satellite (the replacement for IRNSS-1A) remained inside the Polar Satellite Launch Vehicle as its heat shield failed to open during the flight.
Second-gen shift
After orbiting nine IRNSS satellites, ISRO decided to go in for the heavier, second-generation navigation satellites — NVS. Five of these — NVS-01 to -05 — will augment NavIC’s primary constellation with enhanced features for continuity of services.
The NVS series will work alongside the earlier satellites in the L5 and S bands. The L1 band is only in the NVS-01 and -02 satellites.
Of the 10 navigation satellites sent up earlier, only four are fully functional, providing position, navigation and timing services; some are partially functioning, offering safety-of-life messaging services.
One comfort is that a navigation solution requires four satellites, and India has four functional ones.
(The writer is an independent journalist)