Maarg Manthan · Topic 12.30

NASA-ISRO Synthetic Aperture Radar (NISAR) Mission

Science & Technology › Space Technology and ISRO · Topic 12.30

NISAR, the NASA-ISRO Synthetic Aperture Radar, is a joint Earth observation satellite of NASA and ISRO and is the first mission to carry radars of two different frequencies, an L-band radar from NASA with a wavelength of about 24 centimetres and an S-band radar from ISRO with a wavelength of about 12 centimetres. It was launched on 30 July 2025 by GSLV-F16 from Sriharikota into a sun-synchronous orbit at about 743 kilometres. Using a 12-metre deployable mesh reflector antenna and a technique called SweepSAR, it images a swath 242 kilometres wide and covers nearly all land and ice surfaces of the Earth every 12 days, day and night and through cloud, to track changes such as ground movement, ice sheets, forests, crops and disasters.

5 min read · UPSC Prelims · Science & Technology · Space Technology and ISRO

At a Glance

Partners NASA and ISRO
Radars L-band (NASA), S-band (ISRO)
Launched 30 July 2025, GSLV-F16
Orbit About 743 km, sun-synchronous
Repeat cycle 12 days
Exam link UPSC Prelims, Science & Technology: Space Technology and ISRO

Where Does It Fit?

This topic follows the account of space chips. It presents the largest cooperative Earth observation project between India and the United States, which draws on many ideas of radar and remote sensing met earlier. Previous topic: ISRO-Developed Satellite-Based Chip System. Next topic: GSAT-17 as ISRO’s Heaviest Communication Satellite.

What Is NISAR and How Does It Work?

Feature	Details
Partners	NASA and ISRO. NASA built the L-band radar, the antenna reflector, the solid state recorder and the science data system. ISRO built the satellite bus, the S-band radar and the launcher, and operates the satellite
Radar bands	L-band (about 24 cm wavelength) penetrates forests and soil, and S-band (about 12 cm) is more sensitive to small plants and surface roughness
Antenna	A 12 m diameter deployable mesh reflector, the largest ever flown on an Earth observation satellite
SweepSAR	A method that illuminates a wide strip and receives with many beams, giving a swath of about 242 km while keeping fine resolution
Orbit and cycle	Sun-synchronous, about 743 km, 98.4 degrees inclination, repeating every 12 days
Launch	30 July 2025 from the Second Launch Pad at Sriharikota by GSLV-F16
Mission life	Planned for at least three years, with a total cost of about 1.5 billion dollars, among the costliest Earth observation satellites

What Will NISAR Observe?

Ground deformation: radar interferometry measures centimetre scale movements from earthquakes, volcanoes, landslides and land sinking
Ice sheets and glaciers: monitors flow and melt of Greenland and Antarctic ice and Himalayan glaciers
Sea ice and sea level: tracks changes in sea ice and coastal change
Forests and carbon: L-band measures forest biomass and changes in carbon storage
Agriculture: crop growth, soil moisture and wetland changes
Disaster response: maps floods, landslides and damage after earthquakes quickly
Infrastructure: watches settlement of dams, roads and buildings
Free data: NASA and ISRO plan to release data openly, supporting scientists and decision-makers

What Else Should You Remember?

Synthetic aperture radar: a radar that uses motion of the satellite to form a long synthetic antenna, so it gives sharp images, as in Remote Sensing Applications and Ground Segment Services
Why two bands: different wavelengths interact with different features, so using both gives a fuller picture of vegetation and soil
Interferometry: comparing the phase of radar signals from two passes to measure tiny changes in distance
Work share: NASA’s Jet Propulsion Laboratory led its part, and ISRO’s U R Rao Satellite Centre and Space Applications Centre led Indian parts
Earlier mission: the RISAT series gave India its own radar imaging experience, as in Satellite Systems: INSAT, GSAT, IRS (Remote Sensing)
Launch delays: the mission was delayed from the original plans by several years, partly because of the antenna reflector and the coronavirus pandemic
Launch vehicle: GSLV Mk II with indigenous cryogenic stage, as in GSLV Engine Variants and Cryogenic Rocket Technology
Data processing: ground stations in India and the United States process the data
Applications for India: monitoring glacier lake outburst floods, landslides in the Himalayas, subsidence in cities such as Joshimath and crop condition
International role: shows the strength of India-United States space cooperation, along with the Artemis Accords and the Axiom mission with an Indian astronaut
Climate science: helps in measuring the global carbon cycle
Check: operational status and data release details should be checked from official NASA and ISRO sources

Why Does It Matter for the Exam?

Partners and bands: NASA L-band, ISRO S-band
Facts: launch date, rocket, 12-day cycle
Technology: SweepSAR and 12 m antenna
Current affairs link: NISAR data and disaster use
Common errors: saying that NISAR was launched by LVM3 or that it studies the Sun

As an analytical point, NISAR gives a regular, global radar view of the changing Earth. For India, it offers new data on Himalayan hazards, agriculture and coasts, and demonstrates mature partnership in space science.

Why Is This Topic Important?

Partners NASA and ISRO
Technology Two radar bands
Use Hazards and climate

What Came Next?

The last topic of the macro covers GSAT-17, the heavy communication satellite of ISRO. Next topic: GSAT-17 as ISRO’s Heaviest Communication Satellite.

Key People and Terms

SAR Synthetic aperture radar
L-band Long wavelength radar band
S-band Medium wavelength radar band
SweepSAR Wide swath radar technique
InSAR Interferometric SAR
Biomass Plant dry mass

Exam Corner

Points to Remember

NISAR launched: 30 July 2025 by GSLV-F16.
L-band by NASA; S-band by ISRO.
Antenna: 12 m mesh reflector.
Repeat cycle: 12 days.
Swath: about 242 km.

Do Not Confuse With

NISAR and RISAT Joint dual band mission versus ISRO’s earlier radar satellites
L-band and S-band Longer penetrating wavelength versus medium wavelength
SAR and optical imaging Radar through cloud versus light based

Memory Hook

L from NASA, S from ISRO, twelve metres of mesh; every twelve days the whole world is seen.

Mains Angle

Questions ask about the partnership, technology and uses. These points help.

Cooperation India-US partnership
Use Hazards and climate
Technology Dual radar

A Question You May Face

An original practice question, not a past paper question.

“Discuss the significance of the NISAR mission for earth science and for India-United States cooperation in space.”

How to Answer

Facts NISAR basics.
Technology Two bands.
Uses Hazards, forests, ice.
Cooperation Partnership.

GS Relevance

Prelims: NISAR partners, radar bands, launch details, uses. GS Paper 3: science and technology, space, disaster management, international cooperation.

Frequently Asked Questions

What is the NISAR mission?

NISAR, the NASA-ISRO Synthetic Aperture Radar mission, is a joint Earth observation satellite launched on 30 July 2025 by GSLV-F16. It carries two radars, an L-band one from NASA and an S-band one from ISRO, and maps almost all land and ice on Earth every 12 days to measure changes in the surface.

What are the two radar bands of NISAR?

NISAR carries an L-band radar built by NASA with a wavelength of about 24 centimetres and an S-band radar built by ISRO with a wavelength of about 12 centimetres. L-band penetrates vegetation and soil, useful for forest biomass and ground movement, while S-band is sensitive to small crops and surface features.

What is SweepSAR?

SweepSAR is a radar imaging technique used by NISAR in which a wide strip of ground is illuminated and the echo is received by many beams from a large antenna. It allows the satellite to cover a swath of about 242 kilometres wide while keeping fine detail, which is needed to cover the globe every 12 days.

How will NISAR help India?

NISAR will help India to monitor landslides, glaciers and glacial lakes in the Himalayas, subsidence in cities, floods and cyclone damage, crop growth and soil moisture, and forest biomass. Its data, which are planned to be freely available, will support disaster response, agriculture and climate research.

Which rocket launched NISAR?

NISAR was launched by the Geosynchronous Satellite Launch Vehicle, flight GSLV-F16, from the Second Launch Pad of the Satish Dhawan Space Centre at Sriharikota on 30 July 2025. It was placed in a sun-synchronous orbit about 743 kilometres high, an unusual orbit for a GSLV, which usually serves geosynchronous transfer orbits.

PYQ Practice — Statement Analysis

1 NISAR carries an L-band radar built by NASA and an S-band radar built by ISRO.

True

Two frequencies in one satellite.

2 NISAR was launched by LVM3.

False

It was launched by GSLV-F16.

3 NISAR covers nearly all land and ice on Earth every 12 days.