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NASA-ISRO Synthetic Aperture Radar (NISAR) Satellite

29 Jul 2025 GS 3 Science & Technology
NASA-ISRO Synthetic Aperture Radar (NISAR) Satellite Click to view full image

Launch Details

  • Launch Vehicle: GSLV-F16

  • Launch Site: Satish Dhawan Space Centre (SDSC), Sriharikota – Second Launch Pad

  • Orbit: Injected into a 743-km Sun-synchronous orbit (SSO)

  • Weight: 2,392 kg

About the Satellite

  • Joint mission: NASA + ISRO collaboration

  • First-of-its-kind:

    • Uses dual-frequency Synthetic Aperture Radar (SAR):

      • NASA’s L-band SAR

      • ISRO’s S-band SAR

    • Integrated with:

      • NASA’s 12-metre unfurlable mesh reflector antenna

      • ISRO’s modified I3K satellite bus

  • Swathe Width: 242 km

  • Technology Used: SweepSAR technology (First-time use)

SweepSAR 

SweepSAR (Swept Synthetic Aperture Radar) is a radar technique that combines a large deployable antenna with a phased array feed to achieve both wide area coverage and fine spatial resolution in radar imaging. It's a key technology used in the NASA-ISRO Synthetic Aperture Radar (NISAR) mission. It enables wide-area coverage >240km.

Working Principle:

  • Uses a one dimensional phased-array feed with individually controllable radar elements.

  • Operates in two distinct modes:

    1. Transmit Mode:

      • All elements emit a narrow strip of electromagnetic energy simultaneously.

      • This energy strikes the reflector → illuminates a wide 242-km swath on Earth.

    2. Receive Mode:

      • The feed sweeps across the reflector to receive radar echoes from different parts of the swath.

      • Each element receives signals independently, enabling precise time-space localization of echoes.

Unique Capability:

  • Beam sweeping in receive mode helps collect data from a wider area.

  • Allows multi-polarimetric observations with full resolution.

  • Real-time processing of radar echoes by each array element.


Mission Life & Phases

  • Duration: 5 years

  • Mission Phases:

    1. Launch Phase – GSLV-F16 places satellite in SSO.

    2. Deployment Phase – 12-metre reflector antenna deployed via multi-stage boom (extends 9 m from satellite).

    3. Commissioning Phase (First 90 days):

      • Initial checks of mainframe and engineering payload

      • Calibration of SAR instruments by NASA's JPL

    4. Science Operations Phase:

      • Regular orbital maneuvers to maintain SSO

      • Observations and data collection continue until mission end

Applications

  • Earth Observation:

    • All-weather, day-and-night monitoring at 12-day intervals

    • High spatial resolution

  • Capabilities:

    • Detect minor ground deformation, vegetation change, ice sheet dynamics

    • Monitor soil moisture, surface water resources

    • Track shorelines, ship movement, storm characterization

    • Support disaster response and climate resilience planning

Significance

  • Enhances India’s EO (Earth Observation) capabilities.

  • Major step in Indo-US space collaboration under the NASA-ISRO framework.

  • Vital for climate change tracking, agriculture planning, and disaster management.



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