NISAR Earth Observation Satellite

ISRO announced that the NASA–ISRO Synthetic Aperture Radar (NISAR) satellite has officially entered its final science operations phase.

About NISAR Satellite

• NISAR (NASA-ISRO Synthetic Aperture Radar) is the world’s first dual-frequency SAR mission, using both L-band and S-band radars to provide high-resolution, all-weather, day-and-night imaging of Earth.

Key Features

• Dual-Band Radar Capability:
• • L-band radar (1–2 GHz): Developed by NASA, penetrates dense forests and vegetation.
  • S-band radar (2–4 GHz): Developed by ISRO, offers detailed surface imaging.
• Antenna: Equipped with a 12-meter  stationary antenna reflector mounted on a 30-foot (9 m) boom.
• Technology: NISAR uses SweepSAR, allowing efficient and detailed Earth surface mapping over large areas.
  • It will enable NISAR  to  observe earth with a swath of 242 km and high spatial resolution for the first time.

Phases of the Mission

• Four-Phase Structure: The mission consists of Launch, Deployment, Commissioning, and Science Operations.
• Science Phase: This phase begins after commissioning and continues for the satellite’s five-year mission life.
  • The satellite will be maintained in a dedicated science orbit through regular manoeuvres.
  • The phase also involves extensive calibration and validation work to ensure the accuracy and reliability of the radar data.

Key Developments of the Mission

• Antenna Deployment:
  • The 12-meter antenna reflector, essential for both ISRO’s S-Band and NASA’s L-Band SAR payloads, was deployed successfully.
  • The antenna was launched in a stowed configuration on a 9-meter-long boom developed by NASA.
  • Deployment of the boom began on August 9 and was completed by August 15.
• Imaging and Calibration Activities
  • Since August 19, the NISAR S-Band SAR has been imaging the Indian landmass as well as several global calibration and validation sites.
  • Calibration Targets: Ground-based corner reflectors were placed around Ahmedabad and other locations for image calibration.
  • Global Calibration: Data from Amazon rainforests were used to fine-tune spacecraft pointing and SAR imaging accuracy.

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Science and Application Areas

Early analysis demonstrates strong potential for the S-Band SAR data in a wide range of applications, including:

• Agriculture: Crop monitoring, drought assessment
• Forestry: Forest cover, biomass estimation
• Geo-sciences: Land deformation, tectonics, earthquakes
• Hydrology: Flood mapping, water resource assessment
• Cryosphere Studies: Himalayan glacier and snow monitoring
• Oceanic Studies: Coastal erosion, sea-surface roughness, cyclones

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