GSLV Second Stage Flagged Off to Sriharikota for GSLV-F16/NISAR Mission

India’s space programme has taken another significant step forward as the Second Stage (GS2) of the GSLV launch vehicle was officially flagged off on March 24, 2025. The ceremony took place at the ISRO Propulsion Complex (IPRC) in Mahendragiri, with Dr. V. Narayanan, Secretary of the Department of Space (DOS) and Chairman of ISRO, leading the event. Senior officials from the ISRO Propulsion Complex (IPRC) and Vikram Sarabhai Space Centre (VSSC) were also present during this important milestone.

This GS2 stage is crucial for the upcoming GSLV-F16 mission, which is set to launch the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite into space. The NISAR mission is a prestigious joint project between NASA and ISRO, aimed at providing detailed Earth observation data to monitor changes in ecosystems, ice mass, sea levels, and natural disasters.

The Second Stage (GS2) is a liquid-fuel stage of the GSLV (Geosynchronous Satellite Launch Vehicle). It uses a powerful Vikas engine that runs on a combination of UH25 (a mix of unsymmetrical dimethylhydrazine and hydrazine hydrate) and nitrogen tetroxide as propellants. The GS2 stage is designed to ignite after the solid-fueled first stage (S139) burns out, providing the required thrust to carry the satellite further into its orbit.

Specifications of GSLV Second Stage (GS2)

• Engine: Vikas engine

• Propellant Type: Liquid (UH25 and N2O4)

• Propellant Mass: Around 40 tonnes

• Thrust: Approximately 725 kN

• Burn Time: Around 150 seconds

The GS2 stage was transported from Mahendragiri to the launch complex at Sriharikota, where preparations for the GSLV-F16/NISAR mission have already begun in the first week of April 2025. This marks the beginning of a crucial phase in the mission's launch campaign activities.

The NISAR satellite is expected to be one of the most advanced Earth observation satellites ever built, capable of monitoring environmental changes with unmatched accuracy. It carries a dual-frequency radar system, operating in both L-band and S-band, to provide high-resolution data under all weather conditions, day and night.

The successful flagging off and transportation of the GS2 stage underline ISRO’s steady progress toward another landmark launch. The GSLV-F16 mission will not only enhance India’s space capabilities but also strengthen international collaborations in the field of Earth observation and climate monitoring.