Slow recovery: On the ISRO’s GSLV-F18 mission

The GSLV-F18 mission launched the NVS-03 satellite successfully. This mattered because it was only ISRO’s second successful launch of 2026, after 18 difficult months involving two PSLV failures. The mission therefore provided important operational relief.

NVS-03 was reported to be in healthy condition after launch. However, launch success is not the final step. ISRO must manoeuvre the satellite into its intended orbital slot and then commission it for service.

If those steps succeed, NVS-03 can help restore NavIC’s planned capability. The navigation system has been at least one functional satellite short for six months, leaving it unable to provide standalone positioning services over the Indian subcontinent. The mission is therefore both a launch achievement and a potential NavIC rescue.

The GSLV, or Geosynchronous Satellite Launch Vehicle, is designed to place heavier spacecraft into higher geosynchronous-transfer orbits. The PSLV, or Polar Satellite Launch Vehicle, is widely used for satellites headed toward polar and sun-synchronous orbits. Both are expendable rockets developed and operated by ISRO.

Their relationship is not that they are identical vehicles. They are separate launch-vehicle families with different configurations and missions. However, the article states that they share some design aspects. That commonality made the two recent PSLV failures relevant to confidence in the GSLV-F18 mission.

GSLV-F18’s successful launch was therefore important beyond one satellite. It showed a successful mission in a launch-vehicle family connected in design to the PSLV. The result gave ISRO some relief after a constrained 18 months, although the article also highlights wider reliability and capacity problems.

Satellite-navigation systems need enough functioning satellites in suitable orbital positions to provide reliable coverage and calculate a receiver’s location. NavIC’s primary purpose is to provide standalone positioning services over the Indian subcontinent. Being short of at least one functional satellite weakened its ability to meet that purpose.

NVS-03 is intended to add another operational spacecraft to the constellation. Its healthy status after launch is encouraging, but the satellite must first be manoeuvred into its final intended orbital slot. It must then be commissioned, meaning prepared and approved for operational use.

If both steps succeed, NavIC would regain an important part of its planned satellite coverage and service capability. The article calls this a rescue mission because the programme has remained at least one functional satellite short for the last six months. The improvement would depend on successful orbital placement and commissioning.

At the time of the article, ISRO had completed two successful launches in 2026, counting the GSLV-F18 mission. The article describes F18 as only the second successful launch of the year. That unusually low total highlights the pressure on India’s national space programme.

The preceding 18 months had also been affected by two launch failures involving PSLV rockets. PSLV and GSLV share some design aspects, so those failures had consequences beyond the PSLV programme. They contributed to uncertainty around launch reliability while ISRO prepared the F18 mission.

The successful F18 launch offered ISRO some relief, but it did not solve the broader problem. The article notes that two successful orbital missions in five-sixths of a year is inadequate for a programme planning human spaceflight, a space station, and reusable launch vehicles. More capacity and reliability are needed.

The newer NVS satellites carry indigenously made atomic clocks to reduce reliance on imported equipment. The article connects this shift to recommendations from the Parliamentary Standing Committee on Science and Technology and India’s investment in quantum timekeeping. First-generation IRNSS satellites carried imported clocks instead.

Atomic clocks provide extremely precise time references. A navigation satellite transmits a signal with a timestamp. A receiver compares that timestamp with its arrival time and estimates how long the signal travelled. Since radio signals move at a known speed, tiny timing differences become distance estimates. Signals from several satellites then allow the receiver to calculate its position.

Clock errors can create position errors, so stable onboard timing is essential. The three second-generation NVS satellites launched or developed so far are distinguished by having at least one indigenous atomic clock onboard. This supports technological self-reliance and the accuracy needed by NavIC.

The article identifies several linked weaknesses that threaten NavIC and India’s wider space programme. Manufacturing must expand for launch vehicles and replacement satellites. Procurement must become faster, especially for specialised components, qualification tests, and vendor readiness. Workforce growth is also needed because ISRO is described as having an inadequate staff base.

The Electronics Component Manufacturing Scheme and Semiconductor Laboratory modernisation programme could be adjusted for space needs. Dedicated electronics funding is proposed for specialised components and their tests over five to seven years. The article also calls for around ₹17,000 crore for the Department of Space in 2027-28, up from ₹13,705.6 crore in 2026-27.

NavIC needs a dedicated operator so ISRO can focus on its core mandate. India also needs a national space law covering private participation and liability. Together, these measures aim to improve supply chains, replacement capacity, staffing, governance, and mission reliability.

Each navigation satellite broadcasts a radio signal containing its identity, position information, and transmission time. A receiver on Earth records when the signal arrives. By comparing transmission and arrival times, it estimates how long the signal travelled. Multiplying that travel time by the signal’s known speed gives an approximate distance from the satellite.

One distance places the receiver somewhere on a sphere around a satellite. Distances from several satellites produce intersecting spheres, narrowing the possible location. In practice, signals from at least four satellites help determine three-dimensional position and correct the receiver’s clock offset. This process is called trilateration, not triangulation.

The quality of the answer depends on accurate satellite positions, signal timing, and atmospheric corrections. Atomic clocks provide the stable time reference needed aboard satellites. That is why indigenous atomic clocks on the NVS satellites matter for NavIC’s positioning performance and technological independence.