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RISAT-2B Launch - Radar Imaging Satellite

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May 23, 2019

Why in news?

The RISAT-2B satellite was launched with the PSLV-C46 by the Indian Space Research Organisation (ISRO).

What is the RISAT?

  • Two satellites in RISAT (radar imaging satellite) 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.

What are the key features?

  • The RISAT, or radar imaging satellite, is equipped with a sensor known as ‘synthetic aperture radar’, to take "radar images".
  • It works much like the flashlights of a camera, which release visible light to illuminate an object and then use the reflected light to create an image.
  • The synthetic aperture radar transmits hundreds of radio signals (microwave pulses) every second towards the ground.
  • It then captures the signals reflected back by the objects, to create a radio image, which can then be used by computers to build a real image.
  • The moisture and texture of the object will determine the strength of the microwave signal that gets reflected.
  • The strength of the reflected signal will help determine different targets.
  • Likewise, the time between the transmitted and reflected signals will help determine the distance to the object.
  • Unlike visible light, microwaves have longer wavelength and so will not be susceptible to atmospheric scattering.
  • In other words, the very large wavelength radio waves are not obstructed by clouds, dust or other such obstacles in the atmosphere.
  • So they produce reliable images during day and night and all seasons.
  • The RISAT-2B satellite uses X-band synthetic aperture radar for the first time, which was developed indigenously.
  • Unlike the C-band that was used by RISAT-1, the X-band allows for higher resolution imagery for target identification and discrimination.
  • [C-band and X-band are the designations for a band of frequencies in the microwave radio region of the electromagnetic spectrum.]
  • 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.

What is the significance?

  • RISAT-2B adds to India’s capability to observe the earth in all weathers and all conditions.
  • It will enhance India’s monitoring capabilities for civil and military purposes, which include -
    1. crop monitoring during the monsoon season
    2. forestry mapping for forest fires and deforestation
    3. flood mapping as part of the national disaster management programme
  • Given that overcast skies are a constant during monsoon season and 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.
  • Services of such satellites are in great demand from national security agencies as well.

 

Source: Indian Express, The Hindu

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