NISAR: A Landmark Indo-US Earth Observation Mission

Syllabus Areas:

GS III - Science and Technology

The NISAR (NASA-ISRO Synthetic Aperture Radar) satellite is scheduled to launch on July 30, 2025 from Sriharikota using GSLV-F16.

It marks the first dual-band radar satellite mission jointly developed by NASA and ISRO.

The launch comes 50 years after the SITE project, the first Indo-US space collaboration aimed at rural development through satellite-based broadcasting.

What is NISAR?

  • NISAR is an advanced Earth observation satellite designed to detect even minute surface changes across the globe.
  • It uses Synthetic Aperture Radar (SAR) to observe the Earth day and night and through clouds and smoke.
  • The satellite combines NASA’s L-band radar and ISRO’s S-band radar into one platform for high-resolution monitoring.

Objectives of NISAR

  • Monitor earthquakes, landslides, volcanoes, and other geological events.
  • Track glacier movement, snow cover, and glacial lake formation—especially relevant for GLOF (Glacial Lake Outburst Flood)
  • Assess forest density, deforestation, and carbon sequestration using radar that penetrates vegetation.
  • Evaluate crop health, agricultural yield, and losses—supporting food security.
  • Aid in disaster response by detecting changes post-earthquake, flood, oil spill, or wildfire.
  • Monitor coastal erosion, wetland loss, and urban sprawl over time.
NISAR: A Landmark Indo-US Earth Observation Mission

Key Features of NISAR

  • Launch vehicle: GSLV-F16 (ISRO)
  • Launch site: Sriharikota
  • Orbit: 748 km polar sun-synchronous orbit
  • Coverage: 240 km wide swath per scan
  • Repeat cycle: Every 12 days
  • Planned mission life: 3 years
  • Resolution: Detects surface movements of a few centimetres; interferometric accuracy up to millimetres
  • Data generation: 80 TB of data per day (equal to about 150 hard drives of 512 GB)
  • Cost: Approx. $1.5 billion

Technological Innovations

  • Uses Synthetic Aperture Radar (SAR) technology to generate high-resolution images in all weather and lighting conditions.
  • Features dual-band radar:
    • L-band radar (NASA): Penetrates vegetation, ice, and soil. Helps in studying glaciers, subsurface changes, and forest biomass.
    • S-band radar (ISRO): Captures surface details such as crops, buildings, coastlines.
  • Interferometry: By comparing repeated scans, it can measure changes like ground displacement, subsidence, or seismic shifts.
  • Provides a time-series view of Earth's surface changes, much like frames in a moving film.

Applications and Benefits

  • Disaster Management:
    • Early warning for earthquakes, floods, glacial lake outbursts, and landslides.
    • Tracks post-disaster ground movement and damage for better response.
  • Agriculture:
    • Forecasts crop yields and evaluates crop loss.
    • Helps governments plan compensation and food distribution.
  • Climate and Environmental Monitoring:
    • Studies glacial retreat, ice sheet collapse, and snow accumulation.
    • Monitors vegetation growth and forest degradation.
  • Urban and Coastal Planning:
    • Detects coastal erosion and land use changes in cities.
    • Useful for infrastructure planning, especially in vulnerable regions.
  • Ocean and Ship Surveillance:
    • Tracks ship movements, useful for maritime security and illegal fishing detection.

Historical Context: SITE (1975–76)

  • SITE (Satellite Instructional Television Experiment) was a 1-year Indo-US collaboration launched in August 1975.
  • Used NASA’s ATS-6 satellite to beam educational TV content to 2,400 villages in 6 Indian states.
  • Delivered content on agriculture, health, family planning, and primary education in local languages.

Impact of SITE

  • Reached around 2 lakh rural viewers.
  • Helped train 50,000 science teachers.
  • Increased awareness on nutrition, disease prevention, and hygiene.
  • Improved school attendance and learning outcomes in targeted villages.
  • Led to electrification of remote villages to support television infrastructure.
  • Described by Arthur C. Clarke as “the greatest communications experiment in history.”

From SITE to NISAR: 50 Years of Progress

  • In 1975, India used NASA’s satellite; in 2025, India is launching the payload aboard its own rocket.
  • SITE focused on rural development through communication; NISAR focuses on global Earth system monitoring.
  • SITE was a broadcast mission; NISAR is a scientific and observational mission.
  • The collaboration has evolved from a pilot experiment to a cutting-edge space mission with global impact.

Scientific and Strategic Significance

  • Enhances India’s role in global scientific research and disaster resilience.
  • Demonstrates ISRO’s growth from a receiving partner to a technologically capable launcher and developer.
  • Offers free and open access to data for researchers worldwide, supporting international cooperation on climate and sustainability.
  • Strengthens Indo-US relations in space diplomacy and technological innovation.

The launch of NISAR represents a milestone in space-based Earth observation and a testament to 50 years of Indo-US space collaboration. From SITE’s community-focused satellite education to NISAR’s global-scale scientific imaging, this journey showcases how space technology can empower humanity—from the smallest villages to global climate systems.

Prelims Questions:

  1. Which of the following statements about the NISAR satellite mission is/are correct?
    1. NISAR is equipped with Synthetic Aperture Radar (SAR) capable of imaging Earth’s surface during day and night.
    2. NISAR is the first Earth observation satellite developed entirely by ISRO.
    3. NISAR uses dual-band radar systems contributed by both NASA and ISRO.
    1. 1 and 2 only
    2. 1 and 3 only
    3. 2 and 3 only
    4. 1, 2 and 3

    Answer: B. 1 and 3 only

    • Statement 1 is correct – NISAR uses SAR which allows imaging irrespective of lighting conditions.
    • Statement 2 is incorrect – NISAR is a joint NASA-ISRO mission, not developed entirely by ISRO.
    • Statement 3 is correct – NASA provides the L-band radar; ISRO provides the S-band radar.
  2. The 1975 Satellite Instructional Television Experiment (SITE) was significant because:
    1. It was India’s first successful Mars mission
    2. It was the first attempt at direct-to-home television in urban India
    3. It was a joint Indo-US experiment to educate rural India through satellite television
    4. It marked India’s first satellite launch from Sriharikota

    3. Answer: C. It was a joint Indo-US experiment to educate rural India through satellite television

    Explanation: SITE used NASA’s ATS-6 satellite to beam educational content to 2,400 villages in six Indian states, improving awareness on health, agriculture, and education.

  3. What is the primary advantage of NISAR’s dual-band radar system (L-band and S-band)?
    1. It increases the launch speed of the satellite
    2. It allows for two-way communication with rural areas
    3. It enables deeper and more detailed observation of Earth’s surface across different terrains
    4. It reduces the satellite's weight and cost

    4. Answer: C. It enables deeper and more detailed observation of Earth’s surface across different terrains

    Explanation: L-band penetrates deeper through vegetation and snow; S-band captures finer surface features. Together, they allow for comprehensive Earth monitoring.