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RISAT 2B Earth Observation Satellite launched by ISRO

RISAT 2B Earth Observation Satellite launched by ISRO

Tag: GS 3 || Science & Technology || Space || Satellites & Launch Vehicles

Why in news?

  • The RISAT-2B satellite, launched by the Indian Space Research Organisation (ISRO), adds to India’s capability to observe the earth in all weathers and all conditions.


  • Radar imaging satellite: Two satellites in RISAT series have earlier been launched by ISRO.
    • RISAT-2 was the first one to be launched, in 2009, while RISAT-1, which had got delayed, was launched only in 2012.
    • RISAT-1 is no longer operational.
  • After a very long time, ISRO’s PSLV rocket was used to launch just one satellite into space. In recent times, ISRO has been launching multiple satellites at one go.


  • Synthetic aperture radar: The RISAT, or radar imaging satellite, is equipped with a sensor known as ‘synthetic aperture radar’ that takes what are known as ‘radar images’.
  • Works much like flashlights of the camera: Very much like –
    • the flashlights of the camera, which release visible light to illuminate an object and then use the reflected light to create an image,
    • the synthetic aperture radar send out hundreds of radio signals every second towards the subject (in this case, the earth) and capture the reflected signals to create a radio image, which can then be used by computers to build a real image.
  • Microwave pulses: The moisture and texture of the object will determine the strength of the microwave signal that gets reflected.
    • While the strength of the reflected signal will help determine different targets, the time between the transmitted and reflected signals will help determine the distance to the object.
    • Much like the RISAT-1 satellite that was launched by ISRO in April 2012, RISAT-2B will also use microwave radiation.
      • Unlike visible light, microwaves have longer wavelength and so will not be susceptible to atmospheric scattering.
      • Microwave radiation can thus easily pass through the cloud cover, haze and dust, and image the ground.
      • Hence, RISAT-2B satellite will be able to image under almost all weather and environmental conditions.
      • Since it does not rely on visible light for imaging, it will be able to image the ground during both day and night.
    • X-band synthetic aperture radar: The RISAT-2B satellite uses X-band synthetic aperture radar for the first time; the synthetic aperture radar was developed indigenously.
      • Unlike the C-band that was used by RISAT-1, the shorter wavelength of the X-band allows for higher resolution imagery for target identification and discrimination.
      • Since it has high resolution, the satellite will be able to detect objects with dimensions of as little as a metre.
      • This capacity to study small objects and also movement could be useful for surveillance.


  • With the successful pre-dawn launch of RISAT-2B satellite on May 22, the Indian Space Research Organisation (ISRO) has added another feather to its cap.
  • The satellite will enhance India’s capability in –
    • crop monitoring during the monsoon season,
    • forestry mapping for forest fires and deforestation, and
    • flood mapping as part of the national disaster management programme.
  • Given that overcast skies are a constant during the monsoon season and during times of flood, the ability to penetrate the cloud cover is essential.
  • While optical remote sensing that relies on visible light for imaging gets obstructed by clouds, RISAT-2B will not.

Mains question

  • Examine the features and the significance of RISAT 2B Earth observation satellite launched by ISRO.