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Prelims – Science & Technology

1. RISAT-2B satellite is due to be launched on May 22 from Sriharikota.

About Radar Imaging Earth Observation Satellite (RISAT)

1. The RISAT series is the first all-weather earth observation satellites from ISRO.

2. Previous ISRO satellites relied primarily on regular remote-sensing or optical imaging satellites, which work like a light-dependent camera. It cannot perceive hidden or surreptitious objects on the ground and also gets hampered by cloud cover.

3. RISAT satellites are equipped with an active sensor, the synthetic aperture radar (SAR), can sense or ‘observe’ Earth in a special way from space- day and night, rain or cloud.

4. The all-weather seeing feature is crucial for security forces and disaster relief agencies.

5. ISRO orbited its first two radar satellites in 2009 – RISAT-1 and in 2012 – RISAT- 2.

6. RISAT-2B is to be followed by RISAT-2BR1, 2BR2, RISAT-1A, 1B, 2A and so on, at least 6 RISAT series satellites would be launched in 2019 alone.

Reasons for the delay

1. A radar imaging satellite is complex to assemble. Interpreting its images is equally complex.

2. ISRO took almost 10 years to realize RISAT-1. It sends much heavier data than plain remote sensing satellites.

3. However, India has almost kept pace with the world with radar satellites. Worldwide, quite a few countries have planned to launch similar satellites.

Applications of the RISAT-1

1. In India, RISAT imaging has been used for crop estimation because the main crop growing season of Kharif is in May-September when it rains and gets cloudy. 

2. The data has been extensively used for forestry, soil, land use, geology and during floods and cyclone.

Source: The Hindu