Why in News: ISRO is set to launch the NASA-ISRO NISAR satellite on July 30 from Sriharikota aboard a GSLV Mk-II rocket. This marks the first joint Earth-observation mission by NASA and ISRO, aimed at tracking changes on Earth’s surface.
Full form: NASA-ISRO Synthetic Aperture Radar.
Joint Mission: First collaboration between NASA and ISRO on a major Earth-observation satellite.
Dual-Band Radar: First mission using both L-band (1.257 GHz) and S-band (3.2 GHz) synthetic aperture radars.
All-weather Performance: Can penetrate clouds, smoke, and vegetation, and works day and night, in all weather.
What is Synthetic Aperture Radar (SAR)
Working Principle:
- Sends radar pulses to the Earth’s surface.
- Measures return time and phase shift of echoes.
Synthetic Aperture:
- Mimics a giant antenna using onboard movement and signal processing.
- Achieves high resolution without a physically large antenna.
NISAR’s Configuration:
- L-band SAR: Penetrates deep vegetation and soil; tracks ground deformations.
- S-band SAR: Captures fine surface features; ideal for agriculture, soil moisture, water surfaces.
Application Areas of NISAR
1. Solid Earth Processes
- Tracks earthquakes, volcanic activity, and land deformation
- Helps detect fault lines and land subsidence in urban areas
2. Ecosystems
- Monitors forests, wetlands, and natural habitats
- Tracks changes in vegetation cover, deforestation, and biomass
- Supports efforts in biodiversity conservation and carbon stock assessment
3. Ice Dynamics
- Observes glaciers, ice sheets, and polar regions
- Tracks melting patterns, ice flow, and sea-level rise indicators
4. Coastal and Ocean Processes
- Monitors shoreline erosion, flooding, and tidal patterns
- Helps assess coastal vulnerability due to storms and sea-level rise
5. Disaster Response
- Provides rapid damage assessment after disasters (within 5 hours)
- Tracks flooded vs dry land, landslides, and earthquake impact zones
6. Additional Applications
- Monitors groundwater levels, oil reservoirs, and underground shifts
- Observes large infrastructure like dams, levees, and bridges
How Will NISAR Serve India’s Needs?
Although NISAR has global utility, the mission is also customized for India’s national priorities, thanks to ISRO’s dedicated control over the S-band radar. Here’s how:
Agriculture:
- Quarterly maps of active vs inactive cropland.
- Monitoring crop health, yield estimation, and water usage.
Forestry:
- Annual maps of aboveground woody biomass at 1-hectare resolution.
- Helps in carbon stock assessment and tracking deforestation.
Disaster Management:
- Rapid mapping of flooded areas vs dry zones.
- Delivery of damage proxy maps within 5 hours of disaster.
- Monitoring land subsidence, urban risks, and infrastructure integrity.
How Was NISAR Built: The mission is a true collaboration, with equal-scale contributions from both agencies.
ISRO contributed:
- I-3K spacecraft bus (platform for power, propulsion, command systems)
- S-band radar electronics
- Ka-band high-rate telecom system
- Gimballed high-gain antenna
NASA contributed:
- Complete L-band SAR system.
- 12-m wide mesh reflector antenna and 9-m carbon-composite boom.
Electronics and avionics, including:
- GPS receiver
- Solid-state recorder
- Ka-band communication subsystem
- Payload data system
Assembly & Testing:
- Initial radar integration: JPL (Jet Propulsion Lab), USA
- Final integration: ISRO Satellite Centre, Bengaluru
Limitations
- At latitudes above ~60°, ground tracks converge, causing skipped observations.
- About 10% of the Earth’s surface may not be scanned from both directions in a given 12-day cycle.
- Highest resolution modes may not be globally available.
UPSC Relevance
General Studies Paper III –
- Science and Technology: Developments and their applications in everyday life
- Awareness in space technology and related international collaboration
UPSC Mains Practice Question
Q. “India’s participation in the NISAR mission marks a significant leap in the use of space-based technology for sustainable development and disaster preparedness.” Discuss with reference to its applications in agriculture, forestry, and disaster management