GSLV Mk II Mission Overview (June 18, 2025)

India’s next major spaceflight is the June 18, 2025 launch of the NISAR (NASA-ISRO Synthetic Aperture Radar) satellite aboard the GSLV Mk II rocket. The mission is scheduled to lift off from the Satish Dhawan Space Centre (Sriharikota) on June 18, 2025. This liftoff (from the Second Launch Pad) will place NISAR into a Sun-synchronous low Earth orbit for Earth observation. NISAR is a joint NASA-ISRO satellite designed to systematically scan Earth’s land and ice surfaces. Its goal is to monitor ecosystems, ice sheets, and surface deformations (from earthquakes, volcanoes, etc.) with unprecedented precision.

GSLV Mk II: Rocket Specs and Capabilities

Figure: A model of India’s GSLV Mk II launch vehicle (on display in a museum). The Mk II rocket stands about 51.7 meters tall with a lift-off mass around 420 tonnes. It uses four liquid-fueled strap-on boosters (each powered by a Vikas engine) clustered around a central solid core, and a three-stage design including an indigenous cryogenic upper stage. Key performance parameters are:

• Height: ~51.7 m
• Lift-off Thrust: ~7,887 kN (total)
• Stages: 3 stages (solid first + boosters, liquid second, cryogenic third)
• Boosters: 4 liquid strap-ons (Vikas engines)
• Cryogenic Engine (3rd stage): India’s CE-7.5 LH₂/LOX engine (thrust ~75 kN)
• Payload Capacity: ~2,250–2,500 kg to GTO (geostationary transfer orbit); about 5,000–6,000 kg to LEO.

These figures make GSLV Mk II a medium-heavy launcher: it can loft roughly 2.3 t into GTO (e.g. large geostationary communications satellites) and ~5–6 t into low Earth orbit. (By comparison, India’s smaller PSLV launcher handles lighter payloads, while the newer GSLV Mk III heavy-lifter can carry up to ~4 t to GTO.) The Mk II’s first flight was in 2001, and its fully indigenous cryogenic stage was first used in 2014. The robust design (three stages plus boosters) provides the high thrust needed to reach orbit.

NISAR Satellite: Objectives and Payload

Figure: An artist’s concept of the NISAR satellite in orbit (NASA/JPL). NISAR carries two advanced radar instruments – one L-band SAR (provided by NASA) and one S-band SAR (provided by ISRO). Together they can radar-map the Earth’s surface regardless of weather or daylight. NISAR weighs about 2,800 kg and will operate in a polar, Sun-synchronous orbit (~747 km altitude). Its large deployable 12 m antenna reflector will scan nearly the entire Earth’s land and ice cover twice every 12 days.

NISAR’s scientific mission is to measure and map surface changes on global scales. In particular, it will:

• Monitor ecosystems and biomass: track forest growth, deforestation, and land use changes.
• Track ice and water: measure ice-sheet and glacier dynamics, snow cover, and monitor groundwater and sea-level changes.
• Detect natural hazards: map ground deformation from earthquakes, volcanic activity, landslides, and tsunamis.
• Climate and Earth science: provide high-resolution data on changing landscapes, aiding climate models and resource management.

These objectives leverage NISAR’s dual-band capability. NASA notes the $1.5 billion NISAR mission “will measure the Earth’s changing ecosystems, dynamic surfaces and ice sheet collapses, providing information about biomass, sea level rise, groundwater and natural hazards, including earthquakes, tsunamis, volcanoes and landslides”. By combining L-band and S-band data, NISAR can detect centimeter-scale surface movements even through clouds or dense vegetation. All science data (radar images and change maps) will be made freely available shortly after acquisition, enabling researchers and disaster responders worldwide to benefit.

Under the NASA–ISRO partnership (formalized in 2014), each agency built major parts of the satellite. NASA delivered the L-band SAR instrument, high-rate communications and data subsystems, solid-state recorder, and related hardware. ISRO provided the satellite bus and structure, the S-band SAR, and is supplying the GSLV Mk II launch services. In fact, NISAR is the first space mission in history that is jointly built by NASA and ISRO on an Earth science project – a true symbol of international cooperation.

GSLV Program Background

India’s Geosynchronous Satellite Launch Vehicle (GSLV) family was developed to put heavy communication satellites into geostationary orbit. The program began in 2001. Early GSLV rockets (Mark I) used a Russian-made cryogenic upper stage. From 2014 onward, all GSLV Mk II launches have used India’s own CE-7.5 cryogenic engine. This indigenization was a major milestone: India can now fully launch its INSAT and GSAT satellites domestically.

In ISRO’s launch vehicle fleet, GSLV Mk II fills the mid-heavy class. For context:

• PSLV (Polar SLV): India’s versatile medium launcher, routinely sending satellites (~1–1.5 t) to Sun-synchronous orbits.
• GSLV Mk II: Introduced with a domestic cryogenic stage in 2014, capable of ~2.3 t to GTO. It has successfully deployed many ISRO satellites (e.g. GSAT communications series).
• GSLV Mk III (LVM3): India’s newest heavy-lift rocket, three stages with a 5 m fairing. It can carry ~4 t to GTO, and has already launched higher-profile payloads (e.g. Chandrayaan-2, Gaganyaan missions).

Together these vehicles allow ISRO to serve a wide range of missions, from small Earth-observation satellites on PSLV to large commsats and science payloads on GSLV Mk II and Mk III. NISAR represents one of the most ambitious payloads ever assigned to GSLV Mk II.

Mission Significance and Global Collaboration

This NISAR launch is a landmark for India and for world science. For India, it demonstrates mature cryogenic launch capability and supports the country’s growing space ambitions. In press briefings, India’s space leaders noted that these high-profile missions (an astronaut flight and NISAR) underscore a “new era” for the program. Successfully orbiting a nearly 3-tonne radar satellite on a three-stage launcher will be a testament to ISRO’s engineering.

For science, NISAR’s data will be invaluable. Because it repeatedly images the whole globe with high resolution, it will create detailed maps of changing glaciers, forests, wetlands, and coastlines. Open access to NISAR data means researchers worldwide – from climate scientists to disaster management agencies – can monitor floods, earthquakes or deforestation in near real time. NASA emphasizes that NISAR will “deliver critical data” on ice sheets, infrastructure and natural disasters globally.

Perhaps above all, the mission solidifies NASA–ISRO partnership in exploration. NISAR is the first hardware collaboration for an Earth mission between the two agencies. It builds on earlier science cooperation (like Chandrayaan-1 and Mars Orbiter), but is unique in scale and technical sharing. The joint success of NISAR will lay a foundation for future collaborations, from space science to climate studies.

In summary, the June 18, 2025 GSLV-F16 launch of NISAR unites cutting-edge rocketry with global science goals. It leverages India’s heavy-lift rocket (GSLV Mk II) and world-class radar instrumentation to advance our understanding of Earth’s changing environment – a milestone for India and a gift to the world’s scientific community.

Sources: Official mission news and ISRO/NASA publications provide the details above, along with recent coverage by The Times of India and NASA. Each technical fact is cited to these authoritative sources.