ISRO’s 100th rocket launch: A milestone for India’s regional satellite navigation system-OxBig News Network

The Indian Space Research Organisation (ISRO) on Tuesday began its final countdown for the launch of its 100th rocket into space – a milestone in its largely successful exploratory odyssey beyond the Earth’s atmosphere.

A Geosynchronous Satellite Launch Vehicle (GSLV), designated F-15, is scheduled to lift-off from the spaceport at Sriharikota, off the coast of Odisha, at 6:23 pm on January 29. It is carrying the navigation satellite NVS-02 that would form a vital element of India’s independent regional navigation satellite system that has civilian as well as military applications.

GSLV-F15 is the 17th flight of this type of rocket and the 8th operational flight with an indigenous Cryogenic stage engine. Cryogenics are critical because they require optimal functioning at extremely low temperatures – around minus 160 degrees Celsius encountered in outer space.

The GSLV is designed to inject heavy satellites into a geosynchronous transfer orbit which enables them to be maneuvered into a geosynchronous orbit (GSO) about 36,000 km above the Earth.

The GSLV has two variants – Mark-II that can carry payloads weighing up to 2,500 kg into GSO and 6,000 kg to low earth orbit (LEO) at altitudes of about 600 km, and the LVM-III with a payload capacity of 4,000 kg and 8,000 kg respectively.

The NVS-02 will be part of the Navigation with Indian Constellation (NavIC) system designed to provide accurate position, velocity and timing (PVT) service to users in India as well as the region extending about 1,500 km beyond the Indian landmass.

According to ISRO, NavIC is providing two types of services – Standard Positioning Service (SPS) that provides a position accuracy of better than 20 meters and timing accuracy better than 40 nano-seconds over the primary service area, and Restricted Service (RS) through encrypted links available only to authorised users for specific purposes, including the military.

Five second-generation NavIC satellites, NVS-01/02/03/04/05 are envisaged to augment the NavIC base layer constellation with enhanced features for ensuring continuity of services.

It was recognised by the International Maritime Organisation (IMO) as a part of the World-Wide Radio Navigation System (WWRNS) for operation in the Indian Ocean Region in 2020. The potential uses of NavIC listed by ISRO include terrestrial, aerial and marine navigation, disaster management, vehicle tracking and fleet management, integration with mobile phones, and mapping and geodetic data capture.

The NVS satellites additionally incorporate L1 band signals, the most used GPS frequency band for navigation and considered effective for wearable devices, to widen their services. The lead satellite of this series was launched onboard the GSLV F12 on May 29, 2023. It was also for the first time that an indigenous atomic clock was flown into space.

The second, NVS-02, weighing about 2250 kg, is configured with navigation payload in L1, L5 and S bands, which increase interoperability with other satellite-based navigation systems, in addition to a ranging payload in the C-band like its predecessor, the NVS-01.

The L5 is the preferred aeronautical band while the S-band is used for telecommunications, remote sensing, weather monitoring, and scientific research. C-Band is an open general purpose band having a wide reach.

NVS-02 satellite was designed, developed and integrated at ISRO’s UR Satellite Centre (URSC) in collaboration with other satellite-based work centres.

On completion of assembly and integrated testing, it was subjected to a thermos-vacuum test in November-December 2024 to validate its design and performance in a simulated space environment, followed by a dynamic test to determine its ability to withstand the stress load during launch.

The satellite was flagged off to the Satish Dhawan Space Centre in Sriharikota on January 5, 2025 for integration with the rocket and other pre-launch activities. On January 26, ISRO posted on its official X handle that integration of the F-15 and its positioning at the launch-pad was complete.

NVS-02 will replace the IRNSS-1E, the fifth of seven earlier generation spacecrafts in Indian Regional Navigational Satellite System (IRNSS) that had been placed into orbit on January 20, 2016 onboard a Polar Satellite Launch Vehicle.

ISRO is also working on setting up ground stations in countries like Japan, France, and Russia. These additional ground stations will enhance the accuracy and coverage of NavIC signals through better triangulation.

According to ISRO, NavIC signals reach India at a 90-degree angle, making it easier for them to penetrate congested areas, dense forests, and mountainous terrain, and are aimed to reach even remote or hard-to-reach areas. In contrast, GPS signals arrive at an angle, which can sometimes pose challenges for reception in certain locations.

At present, four global navigation networks are available. These are the Global Positioning System (GPS) from the USA, GLONASS from Russia, Galileo from the European Union and BeiDou from China.